UTILIZATION OF A LEFT- VENTRICULAR PRESSURE SENSOR FOR MEASUREMENT OF LEFT-ATRIAL AND AORTIC PRESSURE
CROSS-REFERENCES TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63/614,242, filed December 22, 2023, the full disclosure of which is incorporated herein by reference in its entirety for all purpose.
BACKGROUND
[0001] Ventricular assist devices, known as VADs, are used for both short-term (i.e., days, months) and long-term blood circulation assistance (i.e., years or a lifetime) where a patient's heart is incapable of providing adequate circulation, commonly referred to as heart failure or congestive heart failure. According to the American Heart Association, more than five million Americans are living with heart failure, with about 670,000 new cases diagnosed every year. People with heart failure often have shortness of breath and fatigue. Years of living with blocked arteries and/or high blood pressure can leave a heart too weak to pump enough blood to the body. As symptoms worsen, advanced heart failure develops.
[0002] A patient suffering from heart failure may use a VAD while awaiting a heart transplant or as a long term destination therapy. A patient may also use a VAD while recovering from heart surgery. Thus, a VAD can supplement a weak heart (i.e., partial support) or can effectively replace the natural heart's function.
BRIEF SUMMARY
[0003] The following presents a simplified summary of some systems and methods of the present disclosure in order to provide a basic understanding of the present disclosure. This summary is not an extensive overview of the present disclosure. It is not intended to identify key/critical elements of the present disclosure or to delineate the scope of the present disclosure. Its sole purpose is to present some systems and methods of the present disclosure in a simplified form as a prelude to the more detailed description that is presented later. [0004] Systems and methods described herein are directed to mechanical circulatory assist systems and related methods in which a left ventricular assist device (LVAD) includes a blood flow inlet pressure sensor that measures blood pressure within the left ventricle of a patient. The measured left ventricular blood pressures can be used to monitor blood pressure within the left atrium of the patient over time via determining time frames in which the mitral valve of the patient is open to determine when the left ventricular blood pressures are indicative of the left atrial pressures (i.e., substantially equal due to the mitral valve being open). The measured left ventricular blood pressures can be used to monitor blood pressure within the aorta (when the aortic valve is open) over time via determining time frames in which the aortic valve of the patient is open to determine when the left ventricular blood pressures are indicative of the aortic pressures (i.e., substantially equal due to the aortic valve being open). The measured left ventricular blood pressures can be employed to monitor blood pressure within the aorta by determining pressure of the blood output from the LVAD and calculating pressure loss over an outflow conduit via which the LVAD is fluidly coupled to the aorta. The LVAD can further includes an outlet blood pressure sensor for measuring pressure of the blood output from the LVAD. The measured left ventricular blood pressures can be used in conjunction with the aortic blood pressures to generate aortic valve pressure drop data for use in assessing extent of aortic valve stenosis or incompetence. The measured left ventricular blood pressures, the left atrial blood pressures, the aortic blood pressures, and or the aortic valve pressure drop data can be displayed such that a clinician may select operational parameters for the LVAD and/or assess the hemodynamic status of the patient, and/or can be used in algorithms to automatically adjust operational parameters for the LVAD such as, for example, rotational speed of the LVAD.
[0005] Thus, in one aspect, a mechanical circulatory assist system includes a left ventricular assist device (LVAD) and a controller operatively coupled with the LVAD. The LVAD includes a blood flow inlet, a blood flow outlet, and a blood flow inlet pressure sensor. The LVAD is implantable and operable so that the blood flow inlet receives a blood flow from the left ventricle of a patient and the blood flow is pumped out through the blood flow outlet to the aorta of the patient. The blood flow inlet pressure sensor is configured to measure blood pressure within the blood flow inlet. The controller is configured to control operation of the LVAD to pump the blood flow and process output of the blood flow inlet pressure sensor to generate left ventricular pressure data indicative of blood pressure within the left ventricle over a monitored period of time. [0006] The controller can be configured to output the left ventricular pressure data. For example, the controller can be configured to output the left ventricular pressure data for display and/or further processing.
[0007] The controller can be configured to monitor blood pressure within the left ventricle. For example, the controller can be configured to process the left ventricular pressure data to monitor for one or more instances where the blood pressure within the left ventricle is outside a normal operating range for left ventricular pressure and generate an output indicative of the blood pressure within the left ventricle being outside the normal operating range for left ventricular pressure in response to detection of the one or more instances where the blood pressure within the left ventricle is outside the normal operating range for left ventricular pressure.
[0008] The controller can be configured to monitor blood pressure within the left atrium. For example, the controller can be configured to determine time frames during which the mitral valve of the patient is open; generate left atrial pressure data based on subsets of the left ventricular pressure data corresponding to the time frames during which the mitral valve of the patient is open, wherein the left atrial pressure data is indicative of blood pressure within the left atrium of the patient over the monitored period of time; and output the left atrial pressure data for display and/or further processing. The controller can further be configured to determine the time frames during which the mitral valve of the patient is open based on the left ventricular pressure data. The controller can further be configured to generate blood flow rate data indicative of blood flow rate through the LVAD over the monitored period of time; and determine the time frames during which the mitral valve of the patient is open further based on the blood flow rate data. The LVAD can include a microphone configured to generate output indicative of sounds of opening and closing of the mitral valve and the controller is configured to determine the time frames during which the mitral valve of the patient is open further based on the output of the microphone. The controller can be configured to process the left atrial pressure data to monitor for one or more instances where the blood pressure within the left atrium of the patient is outside a normal operating range for left atrial pressure and generate an output indicative of the blood pressure within the left atrium being outside the normal operating range for left atrial pressure in response to detection of the one or more instances where the blood pressure within the left atrium is outside the normal operating range for left atrial pressure. [0009] The controller can be configured to monitor blood pressure within the aorta. For example, the controller can be configured to determine time frames during which the aortic valve of the patient is open; generate aortic pressure data based on subsets of the left ventricular pressure data corresponding to the time frames during which the aortic valve of the patient is open, wherein the aortic pressure data is indicative of blood pressure within the aorta of the patient over the monitored period of time; and output the aortic pressure data for display and/or further processing. The LVAD can include a microphone configured to generate output indicative of sounds of opening and closing of the aortic valve and the controller is configured to determine the time frames during which the aortic valve of the patient is open further based on the output of the microphone. The controller can be configured to process the aortic pressure data to monitor for one or more instances where the blood pressure within the aorta of the patient is outside a normal operating range for aortic pressure and generate an output indicative of the blood pressure within the aorta being outside the normal operating range for aortic pressure in response to detection of the one or more instances where the blood pressure within the aorta is outside the normal operating range for aortic pressure. The mechanical circulatory assist system can further include an outflow conduit configured for fluidically coupling the blood flow outlet to the aorta of the patient and the controller is configured to generate blood flow rate data indicative of at least one rate of flow of blood through the LVAD, determine a pump pressure differential between the blood flow inlet and the blood flow outlet, determine a pressure loss differential between the blood flow outlet and the aorta based on the blood flow rate data and a flow resistance of the outflow conduit, and generate aortic pressure data indicative of at least one blood pressure within the aorta based on the left ventricular pressure data, the pump pressure differential, and the pressure loss differential. The controller can be configured to process the aortic pressure data to monitor for one or more instances where the blood pressure within the aorta of the patient is outside a normal operating range for aortic pressure and generate an output indicative of the blood pressure within the aorta being outside the normal operating range for aortic pressure in response to detection of the one or more instances where the blood pressure within the aorta is outside the normal operating range for aortic pressure. The LVAD can include a magnetically levitated and rotated blood flow impeller and hall effect sensors for monitoring position and rotation of the blood flow impeller within a blood flow channel of the LVAD and the controller is configured to generate the blood flow rate data and estimate the pump pressure differential based at least in part on output of the hall effect sensors. [0010] The controller can be configured to operate the LVAD so that the aortic valve of the patient opens and closes and generate aortic valve pressure drop data indicative of a pressure drop across the aortic valve while the aortic valve is open based on the left ventricular pressure data and the aortic pressure data. The LVAD can include a microphone configured to generate output indicative of sounds of opening and closing of the aortic valve and the controller is configured to determine time frames during which the aortic valve of the patient is open based on the output of the microphone. The LVAD can include an accelerometer configured to generate output indicative of accelerations generated via opening and closing of the aortic valve of the patient and the controller is configured to determine time frames during which the aortic valve of the patient is open based on the output of the accelerometer.
[0011] The LVAD can further include an outflow conduit and a blood flow outlet pressure sensor. The outflow conduit can be configured for fluidically coupling the blood flow outlet to the aorta of the patient. The blood flow outlet pressure sensor can be configured to measure a blood pressure within the blood flow outlet. The controller can be configured to generate blood flow rate data indicative of at least one rate of flow of blood through the LVAD, estimate an outflow conduit pressure loss differential between the blood flow outlet and the aorta based on the blood flow rate data and a flow resistance of the outflow conduit, and generate aortic pressure data indicative of at least one blood pressure within the aorta based on the blood pressure within the blood flow outlet and the outflow conduit pressure loss differential. The LVAD can include a magnetically levitated and rotated blood flow impeller and hall effect sensors for monitoring position and rotation of the blood flow impeller within a blood flow channel of the LVAD and the controller is configured to generate the blood flow rate data based at least in part on output of the hall effect sensors. The controller can be configured to operate the LVAD so that the aortic valve of the patient opens and closes and generate aortic valve pressure drop data indicative of a pressure drop across the aortic valve while the aortic valve is open based on the left ventricular pressure data and the aortic pressure data. The LVAD can include a microphone configured to generate output indicative of sounds of opening and closing of the aortic valve of the patient and the controller can be configured to determine time frames during which the aortic valve of the patient is open based on the output of the microphone. The LVAD can include an accelerometer configured to generate output indicative of accelerations generated via opening and closing of the aortic valve of the patient and the controller can be configured to determine time frames during which the aortic valve of the patient is open based on the output of the accelerometer.
[0012] In another aspect, a method of monitoring hemodynamic parameters of a patient with an implanted left ventricular assist device (LVAD) is provided. The LVAD includes a blood flow inlet, a blood flow outlet, and a blood flow inlet pressure sensor configured for measuring blood pressure within the blood flow inlet. The method includes operating the LVAD to pump blood from the left ventricle of a patient to the aorta of the patient and processing, by a controller, output of the blood flow inlet pressure sensor to generate left ventricular pressure data indicative of blood pressure within the left ventricle over a monitored period of time.
[0013] The method can include outputting the left ventricular pressure data. For example, the method can include outputting, by the controller, the left ventricular pressure data for display and/or further processing.
[0014] The method can include monitoring blood pressure within the left ventricle. For example, the method can include processing, by the controller, the left ventricular pressure data to monitor for one or more instances where the blood pressure within the left ventricle of the patient is outside a normal operating range for left ventricular pressure and generating, by the controller, an output indicative of the blood pressure within the left ventricle being outside the normal operating range for left ventricular pressure in response to detection of the one or more instances where the blood pressure within the left ventricle is outside the normal operating range for left ventricular pressure.
[0015] The method can include monitoring blood pressure within the left atrium. For example, the method can further include determining, by the controller, time frames during which the mitral valve of the patient is open, generating, by the controller, left atrial pressure data based on subsets of the left ventricular pressure data corresponding to the time frames during which the mitral valve of the patient is open (wherein the left atrial pressure data is indicative of blood pressure within the left atrium of the patient over the monitored period of time) and outputting, by the controller, the left atrial pressure data for display and/or further processing. The controller can be configured to determine the time frames during which the mitral valve of the patient is open based on the left ventricular pressure data. The method can include generating, by the controller, blood flow rate data indicative of blood flow rate through the LVAD over the monitored period of time and determining, by the controller, the time frames during which the mitral valve of the patient is open further based on the blood flow rate data. The method can further include generating, via a microphone, output indicative of sounds of opening and closing of the mitral valve, and the controller can determine the time frames during which the mitral valve of the patient is open further based on the output of the microphone. The method can further include processing, by the controller, the left atrial pressure data to monitor for one or more instances where the blood pressure within the left atrium of the patient is outside a normal operating range for left atrial pressure and generating, by the controller, an output indicative of the blood pressure within the left atrium being outside the normal operating range for left atrial pressure in response to detection of the one or more instances where the blood pressure within the left atrium is outside the normal operating range for left atrial pressure.
[0016] The method can include monitoring blood pressure within the aorta. For example, the method can further include determining, by the controller, time frames during which the aortic valve of the patient is open, generating, by the controller, aortic pressure data based on subsets of the left ventricular pressure data corresponding to the time frames during which the aortic valve of the patient is open (wherein the aortic pressure data is indicative of blood pressure within the aorta of the patient over the monitored period of time) and outputting, by the controller, the aortic pressure data for display and/or further processing. The method can further include generating, via a microphone, output indicative of sounds of opening and closing of the aortic valve. The controller can be configured to determine the time frames during which the aortic valve of the patient is open further based on the output of the microphone. The method can further include processing, by the controller, the aortic pressure data to monitor for one or more instances where the blood pressure within the aorta of the patient is outside a normal operating range for aortic pressure and generating, by the controller, an output indicative of the blood pressure within the aorta being outside the normal operating range for aortic pressure in response to detection of the one or more instances where the blood pressure within the aorta is outside the normal operating range for left atrial pressure. The method can further include generating, by the controller, blood flow rate data indicative of at least one rate of flow of blood through the LVAD, determining, by the controller, a pump pressure differential between the blood flow inlet and the blood flow outlet, determining, by the controller, a pressure loss differential between the blood flow outlet and the aorta based on the blood flow rate data and a flow resistance of an outflow conduit fluidly coupling the blood flow outlet to the aorta, and generating, by the controller, aortic pressure data indicative of at least one blood pressure within the aorta based on the left ventricular pressure data, the pump pressure differential, and the pressure loss differential. The method can further include processing, by the controller, the aortic pressure data to monitor for one or more instances where the blood pressure within the aorta of the patient is outside a normal operating range for aortic pressure and generating, by the controller, an output indicative of the blood pressure within the aorta being outside the normal operating range for aortic pressure in response to detection of the one or more instances where the blood pressure within the aorta is outside the normal operating range for aortic pressure. The method can further include magnetically levitating and rotating a blood flow impeller within a blood flow channel of the LVAD to pump blood from the left ventricle of a patient to the aorta of the patient, monitoring position and rotation of the blood flow impeller within the blood flow channel via hall effect sensors, generating, by the controller, the blood flow rate data based at least in part on output of the hall effect sensors, and estimating, by the controller, the pump pressure differential based at least in part on the output of the hall effect sensors. The method can further include operating the LVAD so that the aortic valve of the patient opens and closes and generating, by the controller, aortic valve pressure drop data indicative of a pressure drop across the aortic valve while the aortic valve is open based on the left ventricular pressure data and the aortic pressure data. The method can further include generating, via a microphone, output indicative of sounds of opening and closing of the aortic valve. The controller can be configured to determine the time frames during which the aortic valve of the patient is open further based on the output of the microphone. The method can further include generating, via an accelerometer, output indicative of accelerations induced via opening and closing of the aortic valve. The controller can be configured to determine the time frames during which the aortic valve of the patient is open further based on the output of the accelerometer. The method can further include generating, by the controller, blood flow rate data indicative of at least one rate of flow of blood through the LVAD, estimating, by the controller, an outflow conduit pressure loss differential between the blood flow outlet and the aorta based on the blood flow rate data and a flow resistance of an outflow conduit fluidly coupling the blood flow outlet to the aorta, and generating, by the controller, aortic pressure data indicative of at least one blood pressure within the aorta based on the blood pressure within the blood flow outlet and the outflow conduit pressure loss differential. The method can further include magnetically levitating and rotating a blood flow impeller within a blood flow channel of the LVAD to pump blood from the left ventricle of a patient to the aorta of the patient, monitoring position and rotation of the blood flow impeller within the blood flow channel via hall effect sensors, and generating, by the controller, the blood flow rate data based at least in part on output of the hall effect sensors.
[0017] The method can include generating aortic valve pressure drop data for assessing the aortic valve. For example, the method can further include operating the LVAD so that the aortic valve of the patient opens and closes and generating, by the controller, aortic valve pressure drop data indicative of a pressure drop across the aortic valve while the aortic valve is open based on the left ventricular pressure data and the aortic pressure data. The method can further include generating, via a microphone, output indicative of sounds of opening and closing of the aortic valve. The controller can be configured to determine the time frames during which the aortic valve is open further based on the output of the microphone. The method can further include generating, via an accelerometer, output indicative of accelerations induced via opening and closing of the aortic valve of the patient. The controller can be configured to determine the time frames during which the aortic valve is open further based on the output of the accelerometer.
[0018] For a fuller understanding of the nature and advantages of the present disclosure, reference should be made to the ensuing detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is an illustration of a mechanical circulatory support system that includes a ventricular assist device (VAD) implanted in a patient’s body, in accordance with the present disclosure.
[0020] FIG. 2 is an exploded view of implanted components of the circulatory support system of FIG. 1.
[0021] FIG. 3 is an illustration of the VAD of FIG. 1 attached to the patient’s heart to augment blood pumping by the patient’s left ventricle.
[0022] FIG. 4 is a cross-sectional view of the VAD of FIG. 3.
[0023] FIG. 5 is an illustration of an example of a control unit for the VAD of FIG. 3. [0024] FIG. 6 is a heart-side view of the control unit of FIG. 5 showing a three-axis accelerometer included in the control unit, in accordance with the present disclosure.
[0025] FIG. 7 is a schematic diagram of a control system architecture, in accordance with the present disclosure, of the mechanical circulatory support system of FIG. 1.
[0026] FIG. 8 is a plot of left ventricular pressure, left atrial pressure, and aortic pressure over a cardiac cycle. [0027] FIG. 9 is a plot of blood flow rate through a blood pump of a left ventricular assist device over a cardiac cycle.
[0028] FIG. 10 is a simplified block diagram of a method of monitoring left atrial pressure via an LVAD with an inlet pressure sensor, in accordance with the present disclosure.
[0029] FIG. 11 illustrates triggering of a notification in response to left atrial pressure trending above a normal operating pressure range for left atrial pressure, in accordance with the present disclosure.
[0030] FIG. 12 is a simplified block diagram of a method of monitoring left atrial pressure via an LVAD with an inlet pressure sensor, in accordance with the present disclosure.
[0031] FIG. 13 is a simplified block diagram of a method of monitoring aortic pressure via an LVAD with an inlet pressure sensor, in accordance with the present disclosure.
[0032] FIG. 14 is a simplified block diagram of a method of assessing an aortic valve via an LVAD with an inlet pressure sensor, in accordance with the present disclosure.
DETAILED DESCRIPTION
[0033] In the following description, various systems and methods of the present disclosure will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present disclosure. However, it will also be apparent to one skilled in the art that systems and methods in accordance with the present disclosure may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the systems and methods being described.
[0034] In systems and methods described herein, a left ventricular assist device (LVAD) includes an inlet pressure sensor for generating left ventricular pressure data for use in measuring hemodynamic parameters of a patient. The hemodynamic parameters can be used to determine adjustments to control operational parameters of the LVAD, either manually by a physician interpreting the displayed values, e.g., on a clinical monitor, or automatically via algorithms devised to adjust pump operation, e.g., adjusting pump rotor speed. Using the approaches described herein, the left ventricular pressure data can be used to directly measure and monitor left ventricular pressure (LVP), intermittently measure left atrial pressure (when the mitral valve of the patient is open), intermittently measure aortic pressure (when the aortic valve of the patient is open), and indirectly measure aortic pressure by accounting for the pressure differential across the LVAD in conjunction with a pressure loss due to blood flow through an outlet conduit via which the LVAD is fluidly coupled with the aorta of the patient. Additionally, for patients with sufficient residual blood pumping capability, the LVAD can be operated at a sufficiently low output so that the pressure generated via natural contraction of the left ventricle of the patient is sufficient to produce opening and closing of the aortic valve of the patient, thereby providing for the generation of aortic valve pressure drop data by subtracting the aortic pressure from the measured left ventricular pressure. The resulting aortic valve pressure drop data may be indicative of extent of stenosis or incompetence of the aortic valve and/or monitored to detect development and/or progression of stenosis or incompetence of the aortic valve.
[0035] Referring now to the drawings, in which like reference numerals represent like parts throughout the several views, FIG. 1 is an illustration of a mechanical circulatory support system 10 that includes a ventricular assist device (VAD) 14 implanted in a patient’s body 12. The mechanical circulatory support system 10 includes the VAD 14, a ventricular cuff 16, an outflow cannula 18, an external system controller 20, and power sources 22. A VAD 14 can be attached to an apex of the left ventricle, as illustrated, or the right ventricle, or a separate VAD can be attached to each of the ventricles of the heart 24. The VAD 14 can be capable of pumping the entire flow of blood delivered to the left ventricle from the pulmonary circulation (i.e., up to 10 liters per minute). Related blood pumps applicable to systems and methods in accordance with the present disclosure are described in greater detail below and in U.S. Patent Nos. 5,695,471, 6,071,093, 6,116,862, 6,186,665, 6,234,772, 6,264,635, 6,688,861, 7,699,586, 7,976,271, 7,997,854, 8,007,254, 8,152,493, 8,419,609, 8,652,024, 8,668,473, 8,852,072, 8,864,643, 8,882,744, 9,068,572, 9,091,271, 9,265,870, and 9,382,908, all of which are incorporated herein by reference for all purposes in their entirety. With reference to FIG. 1 and FIG. 2, the VAD 14 can be attached to the heart 24 via the ventricular cuff 16, which can be sewn to the heart 24 and coupled to the VAD 14. The output of the VAD 14 connects to the ascending aorta via the outflow cannula 18 so that the VAD 14 effectively diverts blood from the left ventricle and propels it to the aorta for circulation through the rest of the patient’s vascular system.
[0036] FIG. 1 illustrates the mechanical circulatory support system 10 during battery 22 powered operation. A driveline 26 that exits through the patient’s abdomen 28 connects the VAD 14 to the external system controller 20, which monitors system 10 operation. Related controller systems applicable to systems and methods in accordance with the present disclosure are described in greater detail below and in U.S. Patent Nos. 5,888,242, 6,991,595, 8,323,174, 8,449,444, 8,506,471, 8,597,350, and 8,657,733, EP 1812094, and U.S. Patent Publication Nos. 2005/0071001 and 2013/0314047, all of which are incorporated herein by reference for all purposes in their entirety. The system 10 can be powered by either one, two, or more batteries 22. It will be appreciated that although the system controller 20 and power source 22 are illustrated outside/extemal to the patient body 12, the driveline 26, the system controller 20 and/or the power source 22 can be partially or fully implantable within the patient 12, as separate components or integrated with the VAD 14. Examples of such modifications are further described in U.S. Patent No. 8,562,508 and U.S. Patent No. 9,079,043, all of which are incorporated herein by reference for all purposes in their entirety. [0037] With reference to FIG. 3 and FIG. 4, the VAD 14 has a circular shaped housing 110 and is shown implanted within the patient 12 with a first face 111 of the housing 110 positioned against the patient's heart 24 and a second face 113 of the housing 110 facing away from the heart 24. The first face 111 of the housing 110 includes an inlet cannula 112 extending into the left ventricle LV of the heart 24. The second face 113 of the housing 110 has a chamfered edge 114 to avoid irritating other tissue that may come into contact with the VAD 14, such as the patient's diaphragm. To construct the illustrated shape of the puck-shaped housing 110 in a compact form, a stator 120 and electronics 130 of the VAD 14 are positioned on the inflow side of the housing toward first face 111, and a rotor 140 of the VAD 14 is positioned along the second face 113. This positioning of the stator 120, electronics 130, and rotor 140 permits the edge 114 to be chamfered along the contour of the rotor 140, as illustrated in at least FIG. 3 and FIG. 4, for example.
[0038] Referring to FIG. 4, the VAD 14 includes a dividing wall 115 within the housing 110 defining a blood flow conduit 103. The blood flow conduit 103 extends from an inlet opening 101 of the inlet cannula 112 through the stator 120 to an outlet opening 105 defined by the housing 110. The rotor 140 is positioned within the blood flow conduit 103. The stator 120 is disposed circumferentially about a first portion 140a of the rotor 140, for example about a permanent magnet 141. The stator 120 is also positioned relative to the rotor 140 such that, in use, blood flows within the blood flow conduit 103 through the stator 120 before reaching the rotor 140. The permanent magnet 141 has a permanent magnetic north pole N and a permanent magnetic south pole S for combined active and passive magnetic levitation of the rotor 140 and for rotation of the rotor 140. The rotor 140 also has a second portion 140b that includes impeller blades 143. The impeller blades 143 are located within a volute 107 of the blood flow conduit such that the impeller blades 143 are located proximate to the second face 113 of the housing 110. [0039] The puck-shaped housing 110 further includes a peripheral wall 116 that extends between the first face 111 and a removable cap 118. As illustrated, the peripheral wall 116 is formed as a hollow circular cylinder having a width W between opposing portions of the peripheral wall 116. The housing 110 also has a thickness T between the first face 111 and the second face 113 that is less than the width W. The thickness T is from about 0.5 inches to about 1.5 inches, and the width W is from about 1 inch to about 4 inches. For example, the width W can be approximately 2 inches, and the thickness T can be approximately 1 inch. [0040] The peripheral wall 116 encloses an internal compartment 117 that surrounds the dividing wall 115 and the blood flow conduit 103, with the stator 120 and the electronics 130 disposed in the internal compartment 117 about the dividing wall 115. The removable cap 118 includes the second face 113, the chamfered edge 114, and defines the outlet opening 105. The cap 118 can be threadedly engaged with the peripheral wall 116 to seal the cap 118 in engagement with the peripheral wall 116. The cap 118 includes an inner surface 118a of the cap 118 that defines the volute 107 that is in fluid communication with the outlet opening 105.
[0041] Within the internal compartment 117, the electronics 130 are positioned adjacent to the first face 111 and the stator 120 is positioned adjacent to the electronics 130 on an opposite side of the electronics 130 from the first face 111. The electronics 130 include circuit boards 131 and various components carried on the circuit boards 131 to control the operation of the VAD 14 (e.g., magnetic levitation and/or drive of the rotor) by controlling the electrical supply to the stator 120. The housing 110 is configured to receive the circuit boards 131 within the internal compartment 117 generally parallel to the first face 111 for efficient use of the space within the internal compartment 117. The circuit boards also extend radially inward towards the dividing wall 115 and radially outward towards the peripheral wall 116. For example, the internal compartment 117 is generally sized no larger than necessary to accommodate the circuit boards 131, and space for heat dissipation, material expansion, potting materials, and/or other elements used in installing the circuit boards 131. Thus, the external shape of the housing 110 proximate the first face 111 generally fits the shape of the circuits boards 131 closely to provide external dimensions that are not much greater than the dimensions of the circuit boards 131.
[0042] With continued reference to FIG. 4, the stator 120 includes a back iron 121 and pole pieces 123a-123f arranged at intervals around the dividing wall 115. The back iron 121 extends around the dividing wall 115 and is formed as a generally flat disc of a ferromagnetic material, such as steel, in order to conduct magnetic flux. The back iron 121 is arranged beside the control electronics 130 and provides a base for the pole pieces 123a-123f.
[0043] Each of the pole piece 123a-123f is L-shaped and has a drive coil 125 for generating an electromagnetic field to rotate the rotor 140. For example, the pole piece 123a has a first leg 124a that contacts the back iron 121 and extends from the back iron 121 towards the second face 113. The pole piece 123a can also have a second leg 124b that extends from the first leg 124a through an opening of a circuit board 131 towards the dividing wall 115 proximate the location of the permanent magnet 141 of the rotor 140. In an aspect, each of the second legs 124b of the pole pieces 123a-123f is sticking through an opening of the circuit board 131. In an aspect, each of the first legs 124a of the pole pieces 123a-123f is sticking through an opening of the circuit board 131. In an aspect, the openings of the circuit board are enclosing the first legs 124a of the pole pieces 123a-123f.
[0044] In a general aspect, the VAD 14 can include one or more Hall sensors that may provide an output voltage, which is directly proportional to a strength of a magnetic field that is located in between at least one of the pole pieces 123a-123f and the permanent magnet 141, and the output voltage may provide feedback to the control electronics 130 of the VAD 14 to determine if the rotor 140 and/or the permanent magnet 141 is not at its intended position for the operation of the VAD 14. For example, a position of the rotor 140 and/or the permanent magnet 141 can be adjusted, e.g., the rotor 140 or the permanent magnet 141 may be pushed or pulled towards a center of the blood flow conduit 103 or towards a center of the stator 120.
[0045] Each of the pole pieces 123a-123f also has a levitation coil 127 for generating an electromagnetic field to control the radial position of the rotor 140. Each of the drive coils 125 and the levitation coils 127 includes multiple windings of a conductor around the pole pieces 123a-123f. Particularly, each of the drive coils 125 is wound around two adjacent ones of the pole pieces 123, such as pole pieces 123d and 123e, and each levitation coil 127 is wound around a single pole piece. The drive coils 125 and the levitation coils 127 are wound around the first legs of the pole pieces 123, and magnetic flux generated by passing electrical current though the coils 125 and 127 during use is conducted through the first legs and the second legs of the pole pieces 123 and the back iron 121. The drive coils 125 and the levitation coils 127 of the stator 120 are arranged in opposing pairs and are controlled to drive the rotor and to radially levitate the rotor 140 by generating electromagnetic fields that interact with the permanent magnetic poles S and N of the permanent magnet 141. Because the stator 120 includes both the drive coils 125 and the levitation coils 127, only a single stator is needed to levitate the rotor 140 using only passive and active magnetic forces. The permanent magnet 141 in this configuration has only one magnetic moment and is formed from a monolithic permanent magnetic body 141. For example, the stator 120 can be controlled as discussed in U.S. Patent No. 6,351,048, the entire contents of which are incorporated herein by reference for all purposes. The control electronics 130 and the stator 120 receive electrical power from a remote power supply via a cable 119 (FIG. 3). Further related patents, namely U.S. Patent Nos. 5,708,346, 6,053,705, 6,100,618, 6,222,290, 6,249,067, 6,278,251, 6,351,048, 6,355,998, 6,634,224, 6,879,074, and 7,112,903, all of which are incorporated herein by reference for all purposes in their entirety.
[0046] The rotor 140 is arranged within the housing 110 such that its permanent magnet 141 is located upstream of impeller blades in a location closer to the inlet opening 101. The permanent magnet 141 is received within the blood flow conduit 103 proximate the second legs 124b of the pole pieces 123 to provide the passive axial centering force though interaction of the permanent magnet 141 and ferromagnetic material of the pole pieces 123. The permanent magnet 141 of the rotor 140 and the dividing wall 115 form a gap 108 between the permanent magnet 141 and the dividing wall 115 when the rotor 140 is centered within the dividing wall 115. The gap 108 may be from about 0.2 millimeters to about 2 millimeters. For example, the gap 108 can be approximately 1 millimeter. The north permanent magnetic pole N and the south permanent magnetic pole S of the permanent magnet 141 provide a permanent magnetic attractive force between the rotor 140 and the stator 120 that acts as a passive axial centering force that tends to maintain the rotor 140 generally centered within the stator 120 and tends to resist the rotor 140 from moving towards the first face 111 or towards the second face 113. When the gap 108 is smaller, the magnetic attractive force between the permanent magnet 141 and the stator 120 is greater, and the gap 108 is sized to allow the permanent magnet 141 to provide the passive magnetic axial centering force having a magnitude that is adequate to limit the rotor 140 from contacting the dividing wall 115 or the inner surface 118a of the cap 118. The rotor 140 also includes a shroud 145 that covers the ends of the impeller blades 143 facing the second face 113 that assists in directing blood flow into the volute 107. The shroud 145 and the inner surface 118a of the cap 118 form a gap 109 between the shroud 145 and the inner surface 118a when the rotor 140 is levitated by the stator 120. The gap 109 is from about 0.2 millimeters to about 2 millimeters. For example, the gap 109 is approximately 1 millimeter. [0047] As blood flows through the blood flow conduit 103, blood flows through a central aperture 141a formed through the permanent magnet 141. Blood also flows through the gap 108 between the rotor 140 and the dividing wall 115 and through the gap 109 between the shroud 145 and the inner surface 108a of the cap 118. The gaps 108 and 109 are large enough to allow adequate blood flow to limit clot formation that may occur if the blood is allowed to become stagnant. The gaps 108 and 109 are also large enough to limit pressure forces on the blood cells such that the blood is not damaged when flowing through the VAD 14. As a result of the size of the gaps 108 and 109 limiting pressure forces on the blood cells, the gaps 108 and 109 are too large to provide a meaningful hydrodynamic suspension effect. That is to say, the blood does not act as a bearing within the gaps 108 and 109, and the rotor is only magnetically levitated. The gaps 108 and 109 can be sized and dimensioned so the blood flowing through the gaps forms a film that provides a hydrodynamic suspension effect. In this manner, the rotor can be suspended by magnetic forces, hydrodynamic forces, or both.
[0048] Because the rotor 140 is radially suspended by active control of the levitation coils 127 as discussed above, and because the rotor 140 is axially suspended by passive interaction of the permanent magnet 141 and the stator 120, no magnetic field generating rotor levitation components are needed proximate the second face 113. The incorporation of all the components for rotor levitation in the stator 120 (i.e., the levitation coils 127 and the pole pieces 123) allows the cap 118 to be contoured to the shape of the impeller blades 143 and the volute 107. Additionally, incorporation of all the rotor levitation components in the stator 120 eliminates the need for electrical connectors extending from the compartment 117 to the cap 118, which allows the cap to be easily installed and/or removed and eliminates potential sources of pump failure.
[0049] In use, the drive coils 125 of the stator 120 generates electromagnetic fields through the pole pieces 123 that selectively attract and repel the magnetic north pole N and the magnetic south pole S of the rotor 140 to cause the rotor 140 to rotate within stator 120. For example, the one or more Hall sensors may sense a current position of the rotor 140 and/or the permanent magnet 141, wherein the output voltage of the one or more Hall sensors may be used to selectively attract and repel the magnetic north pole N and the magnetic south pole S of the rotor 140 to cause the rotor 140 to rotate within stator 120. As the rotor 140 rotates, the impeller blades 143 force blood into the volute 107 such that blood is forced out of the outlet opening 105. Additionally, the rotor draws blood into VAD 14 through the inlet opening 101. As blood is drawn into the blood pump by rotation of the impeller blades 143 of the rotor 140, the blood flows through the inlet opening 101 and flows through the control electronics 130 and the stator 120 toward the rotor 140. Blood flows through the aperture 141a of the permanent magnet 141 and between the impeller blades 143, the shroud 145, and the permanent magnet 141, and into the volute 107. Blood also flows around the rotor 140, through the gap 108 and through the gap 109 between the shroud 145 and the inner surface 118a of the cap 118. The blood exits the volute 107 through the outlet opening 105, which may be coupled to an outflow cannula.
[0050] The VAD 14 can include an inlet pressure sensor 150 within the inlet cannula 112. The inlet pressure sensor 150 is configured to generate an inlet pressure sensor output signal indicative of blood pressure within the blood flow conduit 103 at the inlet opening 101. When the VAD 14 is implanted for use a left ventricular assist device, the inlet cannula 112 extends into the left ventricle of the patient and therefore the inlet pressure sensor output signal is indicative of the left ventricular pressure of the patient. To the extent that the measured pressure differs slightly from left ventricular pressure due to the relatively small resistance within the inflow cannula or the difference between dynamic and static flow, corrections via characterization or calibration can be applied. The inlet pressure sensor 150 can continuously generates the inlet pressure sensor output signal, which can be processed to generate left ventricular pressure data for the patient indicative of the left ventricular pressure of the patient over any suitable monitored period of time.
[0051] Optionally, the VAD 14 can include a microphone 155 configured for generating a microphone output signal that can be processed to identify time frames in which the mitral valve is open (bounded by the sound of opening of the mitral valve and the sound of closing of the mitral valve) and/or time frames in which the aortic valve is open (bounded by the sound of opening of the aortic valve and the sound of closing of the aortic valve). When the VAD 14 is implanted for use a left ventricular assist device, the inlet cannula 112 extends into the left ventricle of the patient and therefore the microphone 155 is positioned to generate output in response to sound waves transmitted through blood within the left ventricle of mitral valve and aortic valve openings and closings. The microphone 155 can continuously generate a microphone output signal, which can be processed to determine time frames in which the mitral valve is open and time frames in which the aortic valve is open over any suitable monitored period of time.
[0052] Optionally, the VAD 14 can include an outlet pressure sensor 160 within the blood flow conduit 103 downstream of the rotor 140. The outlet pressure sensor 160 can be configured to generate an outlet pressure sensor output signal indicative of blood pressure within the blood flow conduit 103 at the outlet opening 105. The outlet pressure sensor 160 can be configured to continuously generate the outlet pressure sensor output signal, which can be processed to generate VAD outlet pressure data indicative of the blood pressure at the outlet opening 105 over any suitable monitored period of time.
[0053] FIG. 5 shows a Hall Sensor assembly 200 for the VAD 14, in accordance with the present disclosure. The Hall Sensor assembly 200 includes a printed circuit board (PCB) 202 and six individual Hall Effect sensors 208 supported by the printed circuit board 202. The Hall Effect sensors 208 are configured to transduce a position of the rotor 140 of the VAD 14. In the illustrated configuration, the Hall Effect sensors 208 are supported so as to be standing orthogonally relative to the PCB 202 and a longest edge of each of the Hall Effect sensors 208 is aligned to possess an orthogonal component with respect to the surface of the PCB 202. Each of the Hall Effect sensors 208 generates an output voltage, which is directly proportional to a strength of a magnetic field that is located in between at least one of the pole pieces 123a-123f and the permanent magnet 141. The voltage output by each of the Hall Effect sensors 208 is received by the control electronics 130, which processes the sensor output voltages to determine the position and orientation of the rotor 140. The determined position and orientation of the rotor 140 is used to determine if the rotor 140 is not at its intended position for the operation of the VAD 14. For example, a position of the rotor 140 and/or the permanent magnet 141 may be adjusted, for example, the rotor 140 or the permanent magnet 141 may be pushed or pulled towards a center of the blood flow conduit 103 or towards a center of the stator 120. The determined position of the rotor 140 can also be used to determine rotor eccentricity or a target rotor eccentricity, which can be used as described in U.S. Patent No. 9,901,666, all of which is incorporated herein by reference for all purposes in its entirety, to estimate flow rate of blood pumped by the VAD 14.
[0054] FIG. 6 is a heart-side view of the control electronics 130 showing an accelerometer 210 included in the control electronics 130, in accordance with the present disclosure. The accelerometer 210 can be a three-axis accelerometer that measures accelerations experienced by the control electronics 130 (and thereby the VAD 14) in three orthogonal axes (i.e., an X-axis 212, a Y-axis 214, and a Z-axis 216). The X-axis 212 and the Y-axis 214 can each be oriented orthogonal to an axis of rotation of the rotor 140, and the Z- axis 216 can be parallel to the axis of rotation of the rotor 140.
[0055] FIG. 7 is a schematic diagram of a control system architecture of the mechanical support system 10. The driveline 26 couples the implanted VAD 14 to the external system controller 20, which monitors system operation via various software applications. [0056] The VAD 14 includes the control electronics 130, the inlet pressure sensor 150, optionally the microphone 155, optionally the outlet pressure sensor 160, the Hall Effect Sensor assembly 200, the motor stator 120, the rotor/impeller 140. The control electronics can include a processor 218, a memory device 220 (which can include read-only memory and/or random access-memory), the accelerometer 210, a motor control unit 222, and a communication unit 224. The memory device 220 can store one or more software applications that are executable by the processor 218 for various functions. For example, the one or more software applications can effectuate control the motor control unit 222 to effectuate radial levitation and rotational drive of the rotor 140 during operation. The one or more programs can effectuate processing of output from the accelerometer 210 and/or operational parameters for the VAD 14 (e.g., drive current, rotational speed, flow rate, pressure differential across the impeller) as described herein to detect and/or measure patient physiological events and/or activity (e.g., patient orientation, patient activity level, heart wall motion, heart sounds, heart rate, respiratory rate, diaphragm contraction, cardiac cycle timing). The one or more programs can effectuate control of the motor control unit 222 to synchronize variation in output of the VAD 14 with the patient’s cardiac cycle timing as described herein. For example, the output of the VAD 14 can be increased over a period of time during ventricular systole so as to augment pumping of blood that occurs via contraction of the ventricle, thereby reducing the associated load on the ventricle. The one or more programs can effectuate control of the motor control unit 222 to vary output of the VAD 14 based on patient activity level. For example, the output of the VAD 14 can be increased in response to increased patient activity and decreased in response to decreased patient activity. The one or more programs can also be used to effectuate processing of the output from the accelerometer 210 and/or the operational parameters for the VAD 14 to generate patient monitoring data and/or VAD monitoring data as described herein. The communication unit 224 provides for wired and/or wireless communication between the VAD 14 and the external system controller 20. The motor control unit 222 can be included in the VAD 14. Alternatively, the motor control unit 222 can be included in the external system controller 20. [0057] The external system controller 20 can in turn be coupled to the batteries 22 or an AC power module 30 that connects to an AC electrical outlet. The external system controller 20 can include a processor 226, a memory device 228 (which can include read-only memory and/or random access-memory), an emergency backup battery (EBB) to power the system (e.g., when the batteries 22 are depleted), one or more display units 230, one or more input/output devices 232, and a communication unit 234, which can have Bluetooth capabilities for wireless data communication. An external computer having a system monitor 32 (which can be operated by a clinician or patient) may further be coupled to the circulatory support system 10 for configuring the external system controller 20, the implanted VAD 14, and/or patient specific parameters; updating software on the external system controller 20 and/or the implanted VAD 14; monitoring system operation; and/or as a conduit for system inputs or outputs.
[0058] The memory device 228 can store one or more software applications that are executable by the processor 226 for various functions. For example, the one or more software applications can effectuate control the motor control unit 222 to effectuate radial levitation and rotational drive of the rotor 140 during operation. The one or more programs can effectuate processing of output from the accelerometer 210 and/or operational parameters for the VAD 14 (e.g., drive current, rotational speed, flow rate, pressure differential across the impeller) as described herein to detect and/or measure patient physiological events and/or activity (e.g., patient orientation, patient activity level, heart wall motion, heart sounds, heart rate, respiratory rate, diaphragm contraction, cardiac cycle timing). The one or more programs can effectuate control of the motor control unit 222 to synchronize variation in output of the VAD 14 with the patient’s cardiac cycle timing as described herein. For example, the output of the VAD 14 can be increased over a period of time during ventricular systole so as to augment pumping of blood that occurs via contraction of the ventricle, thereby reducing the associated load on the ventricle. The one or more programs can effectuate control of the motor control unit 222 to vary output of the VAD 14 based on patient activity level. For example, the output of the VAD 14 can be increased in response to increased patient activity and decreased in response to decreased patient activity. The one or more programs can also be used to effectuate processing of the output from the accelerometer 210 and/or the operational parameters for the VAD 14 to generate patient monitoring data and/or VAD monitoring data as described herein. The communication unit 234 provides for wired and/or wireless communication between the external system controller 20 and the VAD 14 and/or the system monitor 32.
[0059] FIG. 8 is a plot of left ventricular pressure 302, left atrial pressure 304, and aortic pressure 306 over a cardiac cycle. At the start of the cardiac cycle, the atrioventricular (AV) valves are open and blood flows into the left ventricle and the right ventricle from the left atrium and the right atrium, respectively. During ventricular systole, contraction of the ventricles closes the AV valves and increases the ventricular pressures. During left ventricular systole, the left ventricular pressure 302 increases to a level slightly greater than the aortic pressure 306, thereby causing the native aortic valve to open. Continued contraction of the left ventricle ejects blood from the left ventricle, through the native aortic valve, into the aorta. The ejection of blood into the aorta raises the aortic pressure 306, which is slightly lower than the left ventricular pressure 302 over an initial portion of the blood ejection from the left ventricle and slightly higher than the left ventricular pressure 302 over an end portion of the blood ejection from the left ventricle. At the end of the ejection of blood from the left ventricle to the aorta, the native aortic valve closes in response to the left ventricular pressure 302 being slightly less than the aortic pressure 306. Subsequent relaxation of the left ventricle results in a dramatic reduction of the left ventricular pressure 302 down to a level where the left ventricular pressure 302 is slightly less than the left atrium pressure 304, thereby causing the left AV valve to open.
[0060] The flow rate of blood through a blood pump of a ventricular assist device typically varies over a cardiac cycle of a patient in response to variation in the pressure differential across the blood pump during the cardiac cycle. For example, FIG. 9 is a plot of an example blood flow rate 308 through a blood pump of a left ventricular assist device over a cardiac cycle of a patient. The illustrated blood flow rate 308 is for a constant rotational speed operation of the blood pump. The blood flow rate 308 in FIG. 9 is aligned with the cardiac cycle of FIG. 8 to better correlate variation in the blood flow rate 308 with pressure differentials illustrated in FIG. 8. At the start of the cardiac cycle, the blood flow rate 308 is relatively low due to the relatively large differential between the aortic pressure 306 and the left ventricular pressure 302. During the initial portion of ventricular systole, the increase in the left ventricular pressure 302 reduces the differential between the aortic pressure 306 and the left ventricular pressure 302, thereby causing a corresponding increase in the blood flow rate 308 due to the decreased pressure differential across the blood pump. During the ejection of blood from the left ventricle into the aorta, the blood flow rate 308 decreases gradually as the aortic pressure 306 gradually increases relative to the left ventricular pressure 302.
Following the closure of the native aortic valve, the blood flow rate 308 decreases substantially in response to the increased pressure differential across the blood pump resulting from the decrease in the ventricular pressure 302. Following opening of the AV valves, the blood flow rate 308 gradually increases in response to a gradually decreasing pressure differential across the blood pump resulting primarily from a gradually decrease in the aortic pressure 306.
[0061] The rotational speed of a continuous flow blood pump of a VAD is typically limited to avoid inducing a suction event in which blood is extracted from the venticle at an excessive rate. Accordingly, a physician will typically set the rotational speed of the blood pump low enough to ensure that the blood flow rate through the blood pump is low enough to not induce a ventricular suction event.
[0062] Left Ventricular Pressure Data
[0063] The inlet pressure sensor 150 can be used to continuously measure the left ventricular pressure over a monitored period of time. Accordingly, the inlet pressure sensor output signal can be processed to generate left ventricular pressure data that defines the measured ventricular pressure as a function of time, thereby allowing the measured ventricular pressure within any time frame during the monitored period of time to be determined. The left ventricular pressure data can be monitored by any suitable device (e.g., by the LVAD 14 via the processor 218, by the external system controller 20 via the processor 226) to automatically generate a notification in response to the left ventricular pressure increasing above a normal operating range for left ventricular pressure and/or generate a notification in response to the left ventricular pressure decreasing below the normal operating range for left ventricular pressure. The left ventricular pressure data can also be output for display and/or further processing for use in assessing the hemodynamic state of the patient and/or for use in adjusting operational parameters of the LVAD 14.
[0064] Left Atrial Pressure Data
[0065] When the mitral valve of the patient is open (which occurs during ventricular diastole as illustrated in FIG. 8), blood flows from the left atrium into the left ventricle. Except for a relatively small pressure drop occurring across the mitral valve resulting from the flow of blood through the mitral valve, the left atrial pressure is substantially equal to the left ventricle pressure. Accordingly, for time frames when the mitral valve is open, the left atrial pressure data can be set equal to the left ventricular pressure data.
[0066] FIG. 10 is a simplified block diagram of a method 400 of monitoring left atrial pressure via an LVAD with an inlet pressure sensor, in accordance with the present disclosure. While the method 400 is described herein with reference to the LVAD system described herein, the method 400 can be practiced in conjunction with any suitable LVAD system. In act 402, left ventricular pressure (LVP) data is generated. For example, the inlet pressure sensor 150 can be used to continuously monitor blood pressure within the left ventricle over any suitable monitored period of time. Any suitable device can be used to process the output signal from the inlet pressure sensor 150, such as the processor 218 of the VAD 14 or the processor 226 of the external system controller 20. The LVP data can be stored in any suitable form, such as a data table with time and pressure entries for a sequence of times over the monitored period of time. In act 404, time frames when the mitral valve is opened are determined. Any suitable approach can be used to determine the time frames when the mitral valve is open. For example, the LVP data can be processed to identify when the downward slope of the left ventricular pressure changes from a large negative slope to a small negative slope indicative of the opening of the mitral valve as shown in FIG. 8. Optionally, output from the microphone 155 can be processed to identify the sound of opening of the mitral valve in a suitable period of time during which the downward slope of the left ventricular pressure changes from a large negative slope to a small negative slope indicative of the opening of the mitral valve as shown in FIG. 8. Optionally, output from the accelerometer 210 can be processed to identify accelerations induced by opening of the mitral valve in a suitable period of time during which the downward slope of the left ventricular pressure changes from a large negative slope to a small negative slope indicative of the opening of the mitral valve as shown in FIG. 8. Likewise, the LVP data can be processed to identify when the slope of the left ventricular pressure exceeds a suitable positive slope indicative of the closing of the mitral valve at the start of ventricular systole as shown in FIG. 8. Optionally, output from the microphone 155 can be processed to identify the sound of closing of the mitral valve in a suitable period of time during which the slope of the left ventricular pressure attains a suitable positive slope indicative of the closing of the mitral valve at the start of ventricular systole as shown in FIG. 8. Optionally, output from the accelerometer 210 can be processed to identify accelerations induced by closing of the mitral valve in a suitable period of time during which the slope of the left ventricular pressure attains a suitable positive slope indicative of the closing of the mitral valve at the start of ventricular systole as shown in FIG. 8. In act 406, the left atrial pressure data is generated from the left ventricular pressure data by setting the left atrial pressure data equal to the left ventricular pressure data in the time frames in which the mitral valve is open. In act 408, the left atrial pressure data is monitored for occurrences of left atrial pressure values outside of a normal operating range for left atrial pressure. The normal operating range for left atrial pressure can be physician selected to be any suitable range for any particular patient. In response to the occurrence of any suitable number of left atrial pressures falling outside of the normal operating range for left atrial pressure, a notification can be generated and output to alert a health care professional and/or a caregiver of the occurrence. In act 410, the left ventricular pressure data and/or the left atrial pressure data can be output for display or further processing. For example, FIG. 11 shows a plot of left atrial pressure over time and illustrates the left atrial pressure increasing above a normal operating pressure range for left atrial pressure, which can trigger the notification of act 408. When left atrial pressure exceeds a normal operating range for left atrial pressure, it may be indicative of worsening heart failure (e.g., further degradation in the natural output of the patient’s heart) that may require adjustment of the operational parameters of the LVAD to compensate for the reduction in the natural output of the patient’s heart.
[0067] Aortic Pressure Data
[0068] FIG. 12 is a simplified block diagram of a method 500 of monitoring aortic pressure via an LVAD with an inlet pressure sensor, in accordance with the present disclosure. While the method 500 is described herein with reference to the LVAD system described herein, the method 500 can be practiced in conjunction with any suitable LVAD system. In act 502, left ventricular pressure (LVP) data is generated. For example, the inlet pressure sensor 150 can be used to continuously monitor blood pressure within the left ventricle over any suitable monitored period of time. Any suitable device can be used to process the output signal from the inlet pressure sensor 150, such as the processor 218 of the VAD 14 or the processor 226 of the external system controller 20. The LVP data can be stored in any suitable form, such as a data table with time and pressure entries for a sequence of times over the monitored period of time. In act 504, time frames when the aortic valve is opened are determined. Any suitable approach can be used to determine the time frames when the aortic valve is open. For example, output from the microphone 155 can be processed to identify the sound of opening of the aortic valve in a suitable period of time during which the LVP is within a suitable range for opening of the aortic valve. Optionally, output from the accelerometer 210 can be processed to identify accelerations induced by opening of the aortic valve in a suitable period of time during which the LVP is within a suitable range for opening of the aortic valve. Likewise, output from the microphone 155 can be processed to identify the sound of closing of the aortic valve in a suitable period of time during which the LVP is within a suitable range for closing of the aortic valve. Optionally, output from the accelerometer 210 can be processed to identify accelerations induced by closing of the aortic valve in a suitable period of time during which the LVP is within a suitable range for closing of the aortic valve. In act 506, the aortic pressure data is generated from the left ventricular pressure data by setting the aortic pressure data equal to the left ventricular pressure data in the time frames in which the aortic valve is open. In act 508, the aortic pressure data is monitored for occurrences of aortic pressure values outside of a normal operating range for aortic pressure. The normal operating range for aortic pressure can be physician selected to be any suitable range for any particular patient. In response to the occurrence of any suitable number of aortic pressures falling outside of the normal operating range for aortic pressure, a notification can be generated and output to alert a health care professional and/or a caregiver of the occurrence. In act 510, the left ventricular pressure data and/or the aortic pressure data can be output for display or further processing.
[0069] The aortic pressure can be also determined from the blood pressure at the outlet of the LVAD 14 by accounting for the pressure drop over the outflow cannula 18 induced by the flow of blood pumped through the outflow cannula 18 by the LVAD 14. The outlet of the LVAD 14 is fluidly coupled with the aorta by the outflow cannula 18. The pressure drop of the outflow cannula 18 can be estimated using a flow resistance of the outflow cannula 18 (in units of pressure drop per flow rate) multiplied by the rate of flow of the blood pumped through the outflow cannula 18 by the LVAD 14. A suitable flow resistance of the outflow cannula 18 can be determined using any suitable known approach. The flow rate of the blood pumped by the LVAD 14 can also be determined using any suitable know approach based on any suitable operational parameters of the LVAD 14 (e.g., rotational speed, stator drive current, position of the rotor 140 within the blood flow channel 103 as indicated by output from the hall effect sensors 208).
[0070] FIG. 13 is a simplified block diagram of a method 600 of monitoring aortic pressure via an LVAD with an inlet pressure sensor, in accordance with the present disclosure. While the method 600 is described herein with reference to the LVAD system described herein, the method 600 can be practiced in conjunction with any suitable LVAD system. In act 602, the LVAD is operated so that the aortic valve remains closed. In act 604, the inlet pressure sensor 150 is used to generate left ventricular pressure data (e.g., as described herein for act 402). In act 606, flow rate data for the LVAD is generated. The flow rate data for the LVAD is indicative of the flow rate of blood through the LVAD over the monitored period of time and can be stored in a data table with time points and corresponding flow rates. In act 608, outlet pressure data for the LVAD is generated. Any suitable approach can be used to generate the outlet pressure data. For example, pressure differential data for the pump indicative of the increase in blood pressure across the pump can be estimated based on operational parameters of the pump (e.g., rotational speed, stator drive current) and combined with the measured left ventricular pressure data to generate the outlet pressure data. Alternatively, an outlet pressure sensor (e.g., the outlet pressure sensor 160) can be used to directly measure the outlet pressure of the LVAD 14. In act 610, the aortic pressure data is generated by subtracting the pressure loss over the outflow conduit 18 from the outlet pressure data. As described herein the pressure loss over the outflow conduit 18 can be calculated based on the flow of blood pumped through the outflow conduit 18 by the LVAD 14 in conjunction with a suitable flow resistance value for the outflow conduit 18. In act 612, the aortic pressure data is monitored for occurrences of aortic pressure values outside of a normal operating range for aortic pressure. The normal operating range for aortic pressure can be physician selected to be any suitable range for any particular patient. In response to the occurrence of any suitable number of aortic pressures falling outside of the normal operating range for aortic pressure, a notification can be generated and output to alert a health care professional and/or a caregiver of the occurrence. In act 614, the aortic pressure data can be output for display or further processing.
[0071] Aortic Valve Pressure Drop Data
[0072] FIG. 14 is a simplified block diagram of a method 700 of assessing the aortic valve of a patient via an LVAD with an inlet pressure sensor, in accordance with the present disclosure. While the method 700 is described herein with reference to the LVAD system described herein, the method 700 can be practiced in conjunction with any suitable LVAD system.
[0073] In act 702, the LVAD is operated so that the aortic valve opens and closes during ventricular systole. As illustrated in FIG. 8, the difference between the aortic pressure and the left ventricular pressure is maximized during ventricular diastole and minimized during ventricular systole. During ventricular diastole, the LVAD can be operated at a rotational rate that is high enough to prevent retrograde flow through the LVAD while being low enough to produce adequate filling of the left ventricle with blood by the start of ventricular systole. For example, while the mitral valve is open during ventricular diastole, the speed of the LVAD can be controlled to pump a suitably small positive blood flow rate from the left ventricle to the aorta. During an initial phase of ventricular systole (during which the left ventricular pressure is increasing and prior to opening of the aortic valve), the rotational rate of the LVAD can be controlled to produce a suitable start of ventricular systole target aortic pressure that is sufficiently low enough for the natural contraction of the left ventricle to generate left ventricular pressure that exceeds the target aortic pressure to induce opening of the aortic valve. While the aortic valve is open during a middle phase of ventricular systole, the rotational rate of the LVAD at the opening of the aortic valve can be maintained until the aortic valve closes. During an end phase of ventricular systole (during which the aortic valve is closed, the left ventricular pressure is decreasing, and before the opening of the mitral valve at the start of ventricular diastole), the rotational rate of the LVAD can be controlled to produce a suitable end of ventricular systole target aortic pressure.
[0074] In act 704, time frames when the aortic valve is opened are determined. Any suitable approach can be used to determine the time frames when the aortic valve is open. For example, the left ventricular pressure data and the aortic pressure data can be compared to identify a time frame during the initial phase of ventricular systole over which the left ventricular pressure exceeds the aortic pressure. Optionally, output from the microphone 155 can be processed to identify the sound of opening of the aortic valve in a suitable period of time during which the left ventricular pressure is approximately equal to the calculated aortic pressure during the initial phase of ventricular systole. Optionally, output from the accelerometer 210 can be processed to identify accelerations induced by opening of the aortic valve in a suitable period of time during which the left ventricular pressure is approximately equal to the calculated aortic pressure during the initial phase of ventricular systole.
Likewise, the left ventricular pressure data and the aortic pressure data can be compared to identify a time frame during the end phase of ventricular systole over which the aortic pressure exceeds the left ventricular pressure following closure of the aortic valve. Optionally, output from the microphone 155 can be processed to identify the sound of closing of the aortic valve in a suitable period of time during which the left ventricular pressure is approximately equal to the calculated aortic pressure during the end phase of ventricular systole. Optionally, output from the accelerometer 210 can be processed to identify accelerations induced by closing of the aortic valve in a suitable period of time during which the left ventricular pressure is approximately equal to the calculated aortic pressure during the end phase of ventricular systole.
[0075] Acts 706 through 712 correspond to acts 604 through 610. For example, in act 706, the inlet pressure sensor 150 is used to generate left ventricular pressure data (e.g., as described herein for acts 402, 604). In act 708, flow rate data for the LVAD is generated (e.g., as described herein for act 606). In act 710, outlet pressure data for the LVAD is generated (e.g., as described herein for act 608). In act 712, aortic pressure data is generated (e.g., as described herein for act 610). [0076] In act 714, aortic valve pressure drop data is generated. The aortic valve pressure data is calculated by subtracting the aortic pressure from the left ventricular pressure over the time frame during which the aortic valve is open. The aortic valve pressure drop data can include an aortic valve pressure drop for points in time spanning each of the time frames in which the aortic valve is open.
[0077] In act 716, the aortic valve pressure drop data is monitored for occurrences of aortic valve pressure drop values outside of a normal operating range for aortic valve pressure drop. The aortic valve pressure drop can be evaluated at any suitable point in time during any suitable instance of ventricular systole. For example, the maximum observed aortic valve pressure drop during any suitable cardiac cycle can be evaluated relative to baseline aortic valve pressure drops (e.g., for a health aortic valve, for one or more aortic valves with an established extent of stenosis or incompetence) to assess the state of health of the aortic valve. The normal operating range for aortic valve pressure drop can be physician selected to be any suitable range for any particular patient. In response to the occurrence of any suitable number of aortic valve pressure drops falling outside of the normal operating range for aortic valve pressure drop, a notification can be generated and output to alert a health care professional and/or a caregiver of the occurrence. In act 718, the aortic valve pressure drop data can be output for display or further processing.
[0078] Other variations are within the spirit of the present disclosure. Thus, while systems and methods in accordance with the present disclosure are susceptible to various modifications and alternative constructions, certain illustrated systems and methods thereof are shown in the drawings and have been described above in detail. It should be understood, however, that there is no intention to limit systems and methods in accordance with the present disclosure to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the present disclosure, as defined in the appended claims.
[0079] The use of the terms “a” and “an” and “the” and similar referents in the context of describing systems and methods in accordance with the present disclosure (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate systems and methods of the present disclosure and does not pose a limitation on the scope of the present disclosure unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of systems and methods in accordance with the present disclosure.
[0080] Preferred systems and methods of the present disclosure are described herein, including the best mode known to the inventors for carrying out systems and methods of the present disclosure. Variations of those preferred systems and methods of the present disclosure may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for systems and methods in accordance with the present disclosure to be practiced otherwise than as specifically described herein. Accordingly, systems and methods in accordance with the present disclosure include all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the present disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.
[0081] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
[0082] The following relate to numbered aspects of the invention:
1. A mechanical circulatory assist system comprising: a left ventricular assist device (LVAD) comprising a blood flow inlet, a blood flow outlet, and a blood flow inlet pressure sensor, wherein the LVAD is implantable and operable so that the blood flow inlet receives a blood flow from the left ventricle of a patient and the blood flow is pumped out through the blood flow outlet to the aorta of the patient, and wherein the blood flow inlet pressure sensor is configured to measure blood pressure within the blood flow inlet; and a controller operatively coupled with the LVAD, wherein the controller is configured to: control operation of the LVAD to pump the blood flow; and process output of the blood flow inlet pressure sensor to generate left ventricular pressure data indicative of blood pressure within the left ventricle over a monitored period of time. The system of aspect 1, wherein the controller is configured to output the left ventricular pressure data for display and/or further processing. The system of aspect 1, wherein the controller is configured to: process the left ventricular pressure data to monitor for one or more instances where the blood pressure within the left ventricle is outside a normal operating range for left ventricular pressure; and generate an output indicative of the blood pressure within the left ventricle being outside the normal operating range for left ventricular pressure in response to detection of the one or more instances where the blood pressure within the left ventricle is outside the normal operating range for left ventricular pressure. The system of aspect 1, wherein the controller is configured to: determine time frames during which the mitral valve of the patient is open; generate left atrial pressure data based on subsets of the left ventricular pressure data corresponding to the time frames during which the mitral valve of the patient is open, wherein the left atrial pressure data is indicative of blood pressure within the left atrium of the patient over the monitored period of time; and output the left atrial pressure data for display and/or further processing. The system of aspect 4, wherein the controller is configured to determine the time frames during which the mitral valve of the patient is open based on the left ventricular pressure data. The system of aspect 5, wherein the controller is configured to: generate blood flow rate data indicative of blood flow rate through the LVAD over the monitored period of time; and determine the time frames during which the mitral valve of the patient is open further based on the blood flow rate data. The system of aspect 5, wherein: the LVAD comprises a microphone configured to generate output indicative of sounds of opening and closing of the mitral valve; and the controller is configured to determine the time frames during which the mitral valve of the patient is open further based on the output of the microphone. The system of aspect 4, wherein the controller is configured to: process the left atrial pressure data to monitor for one or more instances where the blood pressure within the left atrium of the patient is outside a normal operating range for left atrial pressure; and generate an output indicative of the blood pressure within the left atrium being outside the normal operating range for left atrial pressure in response to detection of the one or more instances where the blood pressure within the left atrium is outside the normal operating range for left atrial pressure. The system of any one of aspects 1 through 8, wherein the controller is configured to: determine time frames during which the aortic valve of the patient is open; generate aortic pressure data based on subsets of the left ventricular pressure data corresponding to the time frames during which the aortic valve of the patient is open, wherein the aortic pressure data is indicative of blood pressure within the aorta of the patient over the monitored period of time; and output the aortic pressure data for display and/or further processing. The system of aspect 9, wherein: the LVAD comprises a microphone configured to generate output indicative of sounds of opening and closing of the aortic valve; and the controller is configured to determine the time frames during which the aortic valve of the patient is open further based on the output of the microphone. The system of aspect 9, wherein the controller is configured to: process the aortic pressure data to monitor for one or more instances where the blood pressure within the aorta of the patient is outside a normal operating range for aortic pressure; and generate an output indicative of the blood pressure within the aorta being outside the normal operating range for aortic pressure in response to detection of the one or more instances where the blood pressure within the aorta is outside the normal operating range for aortic pressure. The system of any one of aspects 1 through 8, further comprising an outflow conduit configured for fluidically coupling the blood flow outlet to the aorta of the patient, and wherein the controller is configured to: generate blood flow rate data indicative of at least one rate of flow of blood through the LVAD; determine a pump pressure differential between the blood flow inlet and the blood flow outlet; determine a pressure loss differential between the blood flow outlet and the aorta based on the blood flow rate data and a flow resistance of the outflow conduit; and generate aortic pressure data indicative of at least one blood pressure within the aorta based on the left ventricular pressure data, the pump pressure differential, and the pressure loss differential. The system of aspect 12, wherein the controller is configured to: process the aortic pressure data to monitor for one or more instances where the blood pressure within the aorta of the patient is outside a normal operating range for aortic pressure; and generate an output indicative of the blood pressure within the aorta being outside the normal operating range for aortic pressure in response to detection of the one or more instances where the blood pressure within the aorta is outside the normal operating range for aortic pressure. The system of aspect 12, wherein: the LVAD comprises a magnetically levitated and rotated blood flow impeller and hall effect sensors for monitoring position and rotation of the blood flow impeller within a blood flow channel of the LVAD; and the controller is configured to generate the blood flow rate data and estimate the pump pressure differential based at least in part on output of the hall effect sensors. The system of aspect 12, wherein the controller is configured to: operate the LVAD so that the aortic valve of the patient opens and closes; and generate aortic valve pressure drop data indicative of a pressure drop across the aortic valve while the aortic valve is open based on the left ventricular pressure data and the aortic pressure data. The system of aspect 15, wherein: the LVAD comprises a microphone configured to generate output indicative of sounds of opening and closing of the aortic valve; and the controller is configured to determine time frames during which the aortic valve of the patient is open based on the output of the microphone. The system of aspect 15, wherein: the LVAD comprises an accelerometer configured to generate output indicative of accelerations generated via opening and closing of the aortic valve of the patient; and the controller is configured to determine time frames during which the aortic valve of the patient is open based on the output of the accelerometer. The system of any one of aspects 1 through 8, wherein the LVAD further comprises an outflow conduit and a blood flow outlet pressure sensor, wherein: the outflow conduit is configured for fluidically coupling the blood flow outlet to the aorta of the patient; the blood flow outlet pressure sensor configured to measure a blood pressure within the blood flow outlet; and the controller is configured to: generate blood flow rate data indicative of at least one rate of flow of blood through the LVAD; estimate an outflow conduit pressure loss differential between the blood flow outlet and the aorta based on the blood flow rate data and a flow resistance of the outflow conduit; and generate aortic pressure data indicative of at least one blood pressure within the aorta based on the blood pressure within the blood flow outlet and the outflow conduit pressure loss differential.
19. The system of aspect 18, wherein: the LVAD comprises a magnetically levitated and rotated blood flow impeller and hall effect sensors for monitoring position and rotation of the blood flow impeller within a blood flow channel of the LVAD; and the controller is configured to generate the blood flow rate data based at least in part on output of the hall effect sensors.
20. The system of aspect 18, wherein the controller is configured to: operate the LVAD so that the aortic valve of the patient opens and closes; and generate aortic valve pressure drop data indicative of a pressure drop across the aortic valve while the aortic valve is open based on the left ventricular pressure data and the aortic pressure data.
21. The system of aspect 20, wherein: the LVAD comprises a microphone configured to generate output indicative of sounds of opening and closing of the aortic valve of the patient; and the controller is configured to determine time frames during which the aortic valve of the patient is open based on the output of the microphone.
22. The system of aspect 20, wherein: the LVAD comprises an accelerometer configured to generate output indicative of accelerations generated via opening and closing of the aortic valve of the patient; and the controller is configured to determine time frames during which the aortic valve of the patient is open based on the output of the accelerometer. 23. A method of monitoring hemodynamic parameters of a patient with an implanted left ventricular assist device (LVAD), the method comprising: operating the LVAD to pump blood from the left ventricle of a patient to the aorta of the patient, wherein the LVAD comprises a blood flow inlet, a blood flow outlet, and a blood flow inlet pressure sensor configured for measuring blood pressure within the blood flow inlet; and processing, by a controller, output of the blood flow inlet pressure sensor to generate left ventricular pressure data indicative of blood pressure within the left ventricle over a monitored period of time.
24. The method of aspect 23, further comprising outputting, by the controller, the left ventricular pressure data for display and/or further processing.
25. The method of aspect 23, further comprising: processing, by the controller, the left ventricular pressure data to monitor for one or more instances where the blood pressure within the left ventricle of the patient is outside a normal operating range for left ventricular pressure; and generating, by the controller, an output indicative of the blood pressure within the left ventricle being outside the normal operating range for left ventricular pressure in response to detection of the one or more instances where the blood pressure within the left ventricle is outside the normal operating range for left ventricular pressure.
26. The method of aspect 23, further comprising: determining, by the controller, time frames during which the mitral valve of the patient is open; generating, by the controller, left atrial pressure data based on subsets of the left ventricular pressure data corresponding to the time frames during which the mitral valve of the patient is open, wherein the left atrial pressure data is indicative of blood pressure within the left atrium of the patient over the monitored period of time; and outputting, by the controller, the left atrial pressure data for display and/or further processing. The method of aspect 26, wherein the controller is configured to determine the time frames during which the mitral valve of the patient is open based on the left ventricular pressure data. The method of aspect 27, further comprising: generating, by the controller, blood flow rate data indicative of blood flow rate through the LVAD over the monitored period of time; and determining, by the controller, the time frames during which the mitral valve of the patient is open further based on the blood flow rate data. The method of aspect 27, further comprising generating, via a microphone, output indicative of sounds of opening and closing of the mitral valve, and wherein the controller determines the time frames during which the mitral valve of the patient is open further based on the output of the microphone. The method of aspect 27, further comprising: processing, by the controller, the left atrial pressure data to monitor for one or more instances where the blood pressure within the left atrium of the patient is outside a normal operating range for left atrial pressure; and generating, by the controller, an output indicative of the blood pressure within the left atrium being outside the normal operating range for left atrial pressure in response to detection of the one or more instances where the blood pressure within the left atrium is outside the normal operating range for left atrial pressure. The method of any one of aspects 23 through 30, further comprising: determining, by the controller, time frames during which the aortic valve of the patient is open; generating, by the controller, aortic pressure data based on subsets of the left ventricular pressure data corresponding to the time frames during which the aortic valve of the patient is open, wherein the aortic pressure data is indicative of blood pressure within the aorta of the patient over the monitored period of time; and outputting, by the controller, the aortic pressure data for display and/or further processing. 32. The method of aspect 31, further comprising generating, via a microphone, output indicative of sounds of opening and closing of the aortic valve, and wherein the controller determines the time frames during which the aortic valve of the patient is open further based on the output of the microphone.
33. The method of aspect 31, further comprising: processing, by the controller, the aortic pressure data to monitor for one or more instances where the blood pressure within the aorta of the patient is outside a normal operating range for aortic pressure; and generating, by the controller, an output indicative of the blood pressure within the aorta being outside the normal operating range for aortic pressure in response to detection of the one or more instances where the blood pressure within the aorta is outside the normal operating range for left atrial pressure.
34. The method of any one of aspects 23 through 30, further comprising: generating, by the controller, blood flow rate data indicative of at least one rate of flow of blood through the LVAD; determining, by the controller, a pump pressure differential between the blood flow inlet and the blood flow outlet; determining, by the controller, a pressure loss differential between the blood flow outlet and the aorta based on the blood flow rate data and a flow resistance of an outflow conduit fluidly coupling the blood flow outlet to the aorta; and generating, by the controller, aortic pressure data indicative of at least one blood pressure within the aorta based on the left ventricular pressure data, the pump pressure differential, and the pressure loss differential.
35. The method of aspect 34, further comprising: processing, by the controller, the aortic pressure data to monitor for one or more instances where the blood pressure within the aorta of the patient is outside a normal operating range for aortic pressure; and generating, by the controller, an output indicative of the blood pressure within the aorta being outside the normal operating range for aortic pressure in response to detection of the one or more instances where the blood pressure within the aorta is outside the normal operating range for aortic pressure. 36. The method of aspect 34, further comprising: magnetically levitating and rotating a blood flow impeller within a blood flow channel of the LVAD to pump blood from the left ventricle of a patient to the aorta of the patient; monitoring position and rotation of the blood flow impeller within the blood flow channel via hall effect sensors; generating, by the controller, the blood flow rate data based at least in part on output of the hall effect sensors; and estimating, by the controller, the pump pressure differential based at least in part on the output of the hall effect sensors.
37. The method of aspect 34, further comprising: operating the LVAD so that the aortic valve of the patient opens and closes; and generating, by the controller, aortic valve pressure drop data indicative of a pressure drop across the aortic valve while the aortic valve is open based on the left ventricular pressure data and the aortic pressure data.
38. The method of aspect 37, further comprising generating, via a microphone, output indicative of sounds of opening and closing of the aortic valve, and wherein the controller determines the time frames during which the aortic valve of the patient is open further based on the output of the microphone.
39. The method of aspect 37, further comprising generating, via an accelerometer, output indicative of accelerations induced via opening and closing of the aortic valve, and wherein the controller determines the time frames during which the aortic valve of the patient is open further based on the output of the accelerometer.
40. The method of any one of aspects 23 through 30, further comprising generating, by the controller, blood flow rate data indicative of at least one rate of flow of blood through the LVAD; estimating, by the controller, an outflow conduit pressure loss differential between the blood flow outlet and the aorta based on the blood flow rate data and a flow resistance of an outflow conduit fluidly coupling the blood flow outlet to the aorta; and generating, by the controller, aortic pressure data indicative of at least one blood pressure within the aorta based on the blood pressure within the blood flow outlet and the outflow conduit pressure loss differential. The method of aspect 40, further comprising: magnetically levitating and rotating a blood flow impeller within a blood flow channel of the LVAD to pump blood from the left ventricle of a patient to the aorta of the patient; monitoring position and rotation of the blood flow impeller within the blood flow channel via hall effect sensors; and generating, by the controller, the blood flow rate data based at least in part on output of the hall effect sensors. The method of aspect 40, further comprising: operating the LVAD so that the aortic valve of the patient opens and closes; and generating, by the controller, aortic valve pressure drop data indicative of a pressure drop across the aortic valve while the aortic valve is open based on the left ventricular pressure data and the aortic pressure data. The method of aspect 42, further comprising generating, via a microphone, output indicative of sounds of opening and closing of the aortic valve, and wherein the controller determines the time frames during which the aortic valve is open further based on the output of the microphone. The method of aspect 42, further comprising generating, via an accelerometer, output indicative of accelerations induced via opening and closing of the aortic valve of the patient, and wherein the controller determines the time frames during which the aortic valve is open further based on the output of the accelerometer.