US20040173222A1 - Magnetic pellets and external electromagnetic device for assisting left ventricular contraction, method of pellet insertion, and method of ventricular electromagnetic assistance - Google Patents

Abstract

A magnetic pellet for use in treating a patient's congestive heart includes a contact portion and a plurality of wings. Each wing has a distal end portion hingedly connected to the contact portion and a proximal end portion. The proximal end portions bend toward each other when an electromagnetic field is applied to the pellet. A method of inserting the pellets into a myocardial wall of a heart includes supplying an electromagnetic field to the pellet attached to a distal end of an electromagnetic rod positioned within a delivery catheter, positioning the magnetic pellet at a target area on the myocardial wall; using an injection syringe, positioned at a proximal end of the catheter, to force the pellet into the myocardial wall; and removing the electromagnetic field previously supplied to the pellet and thereby causing the spring-wings to open.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This application claims priority to U.S. Provisional Patent Application Serial No. 60/285,707 filed on Apr. 24, 2001.[0001]
BACKGROUND OF THE INVENTION
• 1. Field of the Invention[0002]
• The present invention relates to the field of artificially stimulating contraction in the heart. More particularly, the invention relates to a device and a method for stimulating electromagnetically contraction of the left ventricle.[0003]
• 2. Description of the Related Art[0004]
• Despite the significant progress in prevention and medical treatment of cardiovascular disease, congestive heart failure (CHF) affects about 1 percent of adults in the United States (i.e. approximately 4-5 million patients), with 400,000 new cases occurring each year. CHF is the primary diagnosis for about 1 million hospitalizations each year and is a contributing factor in over 250,000 deaths annually. The age-adjusted death rate from CHF is 106.4 per 100,000. The median survival, after diagnosis, is 1.7 years for men and 3.2 years for women; the five year survival rate is less than 50 percent. It is estimated that nearly 60,000 patients annually in the United States could benefit from heart transplantation or long-term mechanical support. Evaluation and care of CHF patients costs our society in excess of $11 billion each year.[0005]
• Currently, heart transplantation is considered the most effective therapy for end-stage CHF. However, heart transplantation presents multiple problems, including: (1) a shortage of donor hearts; (2) a significant perioperative morbidity/mortality rate; (3) the requirement of immune suppression; and (4) a less than ideal long-term survival rate. Accordingly, there is a crucial need for the development of alternatives to heart transplantation.[0006]
• Mechanical support by means of implantable ventricular assist devices presently is the most promising alternative to heart transplantation. Currently available assist devices include extracorporeal oxygenators, univentricular and biventricular extracorporeal devices, and total artificial hearts. Most of these devices require the patients to be connected to cumbersome drive systems which makes their use limited only to hospital in-patients.[0007]
• Lately, the development of an implantable left ventricular assist device (LVAD) and the development of wearable power supplies for this device has made the following possible: (1) a patient's rehabilitation; (2) unrestricted patient mobility; (3) patient discharge to the home; and (4) a patient's ability to return to work. However, while an LVAD may have some advantages over heart transplantation, an LVAD still presents many serious limitations for long-term use. These limitations include: (1) selection of patients (i.e., an LVAD is only available to patients without end-organ failure and qualification for an LVAD is as restricted as heart transplantation); (2) an LVAD is unavailable for patients on long-term glucocorticoid therapy or patients with a small body surface area; (3) it is difficult to assess a patient's ability to manage an LVAD; (4) early post-operative complications such as bleeding, right heart failure, air embolism, and multiple organ failure are possible; and (5) late post-operative complications such as infection, thromboembolism, and LVAD failure are also possible.[0008]
• For these and other reasons, a new device is needed which can assist contraction of the left ventricle, which is available to a wide variety of patients, and which does not cause at least some of the early and late post-operative complications previously mentioned.[0009]
SUMMARY OF THE INVENTION
• A virtual ventricular assist device (VVAD), herein disclosed, is designed to overcome many of the aforementioned limitations of an LVAD. For long-term use, a VVAD: (1) can be used for CHF patients without structural defects (i.e., congenital or acquired valvular diseases); (2) requires no major surgery to implant and, therefore, avoids the early complications mentioned above; (3) requires no foreign materials to interact with the surface of the ventricular cavity or conduit vessels and, therefore, avoids the late complications mentioned above; (4) can be used for the right as well as the left ventricle; and (5) eliminates the need for anticoagulants.[0010]
• The VVAD consists of essentially two components: (a) implantable magnetic pellets implanted through a delivery catheter; and (b) an external electromagnetic device which, when cyclically charged, attracts or repels the pellets depending on their corresponding charge. The term “pellet” is not to be limited to ball shaped materials; it is to be construed to include many other shapes including that of a plate or umbrella. Moreover, the pellets are “magnetic” in the sense that they react to magnetic fields in a manner similar to metals due to the presence of free electrons which orient themselves in response to a magnetic field; the pellets themselves are not charged.[0011]
• The implantable pellets are spring-winged, contain materials which are responsive to magnetic fields, and are vacuum-sealed within a polyurethane membrane (or any other biologically inert, synthetic material). The pellets have a myocardial wall contact portion to which a plurality of wings is hingedly connected. Preferably, the pellets are deployed percutaneously to the mid-layer of the targeted myocardial wall through a major artery using a delivery catheter. It is also possible to implant the pellets through the chest wall and into a mid-layer of the targeted myocardium; this transthoracic implantation requires a minimally invasive surgical procedure using a thoracic endoscope. It is also possible to fix the pellets to the outside of the myocardial wall. Pellets made of diamagnetic metals (e.g., bismuth or antimony) are implanted in or on the posterior wall of the left ventricle (LV) whereas pellets made of ferromagnetic metals (e.g., iron or cobalt) are implanted in or on the anterior wall of the left ventricle. The shape of the pellet will depend on the location in which they are fixed and by the method by which they are introduced into the ventricle. For example, in a transthoracic approach, the implantable magnetic pellets can be plate shaped or umbrella shaped like a shell so that they can be implanted on the surface of the targeted myocardium.[0012]
• The external electromagnetic device (which is battery operated and light enough to be worn in the chest wall) generates an electromagnetic force which is synchronized with an EKG, at least one lead of which monitors the user's heart rate. This electromagnetic device may be external or internal to the chest wall. Onset of the force corresponds to the EKG's R wave whereas offset of the force corresponds to the EKG's T wave. Due to the charge of the electromagnetic field, pellets implanted in the posterior wall of the left ventricle will be pulled toward the electromagnetic device while the pellets in the anterior wall of the left ventricle will be correspondingly pushed away from the electromagnetic device. Due to this opposite motion, a compression of the left ventricle occurs. When the electromagnetic field is discontinued (due to the occurrence of the EKG T wave), the anterior and posterior walls of the left ventricle (which hold the magnetic pellets) return to their original positions. In this fashion, a cyclical compression of the left ventricle occurs thereby allowing the left ventricle to beat as if it were normal and healthy. This synchronized generation of electromagnetic force is designed to boost systolic pumping only during the early half of systole. Moreover, the magnitude of the electromagnetic force generated and its domain are adjusted to boost systolic function by 10-20 percent.[0013]
• Pellets are implanted into the myocardium after being introduced into the body via a delivery catheter. The delivery catheter contains a mobile electromagnetic rod which is approximately 7 mm in length. The delivery catheter (preferably size 7 FOD, 120 cm) can be introduced into the body by means of a introducer catheter set which can be any commercially available percutaneous introducer set of size 8 F. If the delivery catheter can be introduced percutaneoulsy through a femoral artery, it is guided into the left ventricle by an external magnetic system working in conjunction with a fluorscope. In the alternative, the delivery catheter can be introduced through a transthoracic-epicardial route; this is a video-assisted method in which the pellets are implanted trans-epicardially into the targeted myocardium.[0014]
• A spring-winged pellet is attached to the distal end of the electromagnetic rod. A wire (within the catheter) connects the proximal end of rod to an electromagnetic power generator and thereby supplies current to the rod; the current charges the electromagnetic rod thereby creating an electromagnetic field around the rod. The electromagnetic field causes the wings of the spring-winged pellet to overcome their otherwise extended orientation and thereby to collapse on the electromagnetic rod. The pellet is maintained in this fashion until it is positioned within the myocardium. When the pellet (attached to the catheter tip) is positioned against the targeted myocardial wall position, the catheter tip is forcefully anchored against the endo-myocardial wall by an external magnet. An injection syringe then hydraulically forces the rod with the pellet into the myocardium. When the pellet is placed within the myocardium, the current supplied to the electromagnetic rod via the wire is discontinued causing the wings to open thereby preventing the pellet from travelling backwards (i.e., in the direction of the delivery catheter when the catheter is removed). After the wings have opened, the rod is hydraulically pulled back into the catheter which is then removed from the body.[0015]
• In this fashion, pellets should be deployed one at a time. In addition, 3 or 4 pellets (or as many as needed) should be positioned in each ventricular myocardial wall (i.e., anterior and posterior) and should be distributed to cover 6-15 square cm of myocardial area.[0016]
• The present invention includes a novel magnetic spring-winged pellet, a method of inserting the pellet, and a method of treating congestive heart failure using spring-winged pellets implanted in or on the myocardial walls of a ventricle in conjunction with an external electromagnetic field generator.[0017]
• One embodiment of the spring-winged pellet includes: (a) a contact portion; and (b) a plurality of wings. In this embodiment each wing has a distal end portion hingedly connected to the contact portion and each wing has a proximal end portion which bends toward the proximal end portions of the other wings when an electromagnetic field is applied to the pellet.[0018]
• One method of inserting a magnetic pellet into a myocardial wall of a heart includes: (a) supplying an electromagnetic field to the pellet which has a plurality of spring-wings and which is attached to a distal end of an electromagnetic rod which is positioned within a delivery catheter; (b) positioning the magnetic pellet at a target area on the myocardial wall; (c) using an injection syringe positioned at a proximal end of the catheter to force the pellet into the myocardial wall; and (d) removing the electromagnetic field previously supplied to the pellet and thereby causing the spring-wings to open. Preferably, the myocardial wall into which the pellets are inserted is in the heart's left ventricle. Moreover, the wall can be either a posterior wall or an anterior wall of the left ventricle. However, the pellets may also be inserted into the myocardial wall of the right ventricle wall using a transthoracic insertion. The electromagnetic field is preferably created by external electromagnetic generator which is electrically connected to a proximal end of the electromagnetic rod by a wire. Finally, this method can be practiced by introducing the delivery catheter to the target area of the myocardial wall by sending the catheter through a femoral artery or by transthoracically sending the catheter through a chest wall.[0019]
• Finally, a preferred method of treating a patient's congestive heart failure includes: (a) positioning a first plurality of magnetic spring-winged pellets in a myocardium of posterior wall of a ventricle of a heart; (b) positioning a second plurality of magnetic spring-winged pellets in a myocardium of an anterior wall of a ventricle of a heart; (c) using an electromagnetic generator to cyclically generate an electromagnetic field which magnetically interacts with the first and the second plurality of pellets; (d) magnetically pulling, in response to the cyclical electromagnetic field, the first plurality of pellets toward the electromagnetic generator; and (e) magnetically pushing, in response to the cyclical electromagnetic field, the second plurality of pellets away from the electromagnetic generator. Ideally, this method also includes: (f) positioning an EKG monitor on the patient and generating a waveform of the heart's electrical activity; and (g) synchronizing the cyclical electromagnetic field to correspond to the heart's electrical activity.[0020]
• These and other features, aspects, and advantages of the present invention will become more apparent from the following description, appended claims, and accompanying exemplary embodiments shown in the drawings.[0021]
BRIEF DESCRIPTION OF THE DRAWINGS
• The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the description, serve to explain the principles of the invention.[0022]
• FIG. 1[0023]ais a longitudinal view of an electromagnetic rod to which a pellet is attached such that the spring-wings are collapsed on the sides of the rod; FIG. 1bis a longitudinal view of the electromagnetic rod of FIG. 1ain which the electromagnetic field supplied to the pellet has been removed causing the spring-wings to open;
• FIG. 2[0024]ais an end view of a magnetic pellet showing the spring-wings in a collapsed orientation; FIG. 2bis an end view of a discharged pellet showing the spring-wings in an open orientation;
• FIG. 3 is a longitudinal view of a delivery catheter containing an electromagnetic rod to which a pellet is attached;[0025]
• FIG. 4 is a longitudinal view of the delivery catheter of FIG. 3 in which an injection syringe is positioned at a proximal end of the catheter; and[0026]
• FIG. 5 is a cross-sectional view of a left ventricle of a heart in which magnetic pellets have been placed in the anterior and posterior myocardial walls.[0027]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
• Reference will now be made in detail to a presently preferred embodiment of the invention, which is illustrated in the drawings. An effort has been made to use the same reference numbers throughout the drawings to refer to the same or like parts.[0028]
• FIGS. 1A-2B detail an[0029]electromagnetic pellet10 which is inserted into a left ventricle20 (shown in FIG. 5) of a patient. Thepellets10 react to magnetic fields in a manner similar to metals due to the presence of free electrons which orient themselves in response to a magnetic field; thepellets10 themselves are not charged. The structure of the two sets ofpellets10 will be described herein will be identical; the only difference is that one of the sets ofpellets10 are diamagnetic (e.g., bismuth or antimony) and the other set ofpellets10 is ferromagnetic (e.g., iron or cobalt).
• The[0030]pellet10 is formed of a plurality ofwings12 and a sharppointed contact portion14. For reasons which will hereafter be described in detail, thepellet10 has two configurations: a closed configuration (FIG. 1A, 2A) in which thewings12 approach each other; and an open configuration (FIGS. 1B, 2B) in which thewings12 project away from each other.
• Although the[0031]pellet10 has at least twowings12, it is preferable to have at least fourwings12. Each of thewings12 has adistal end16 and a proximal18. The distal ends16 of thewings12 are hingedly attached to thecontact portion14 of thepellet10. The proximal18 is preferably blunt so that the plurality ofwings12 may act as a barb when thepellet10 is in the open configuration.
• The[0032]wings18 are biased toward the open configuration, such bias can be achieved according to a number of conventional mechanisms including a living hinge, being spring loaded, etc. However, it is preferable that thewings12 be biased by a living hinge. This bias, however, can be overcome as later explained. When in the closed position, thepellet10 has a height H of approximately 1.5 mm. In the open position, however, thepellet10 has a height of approximately 4.0-5.0 mm.
• The[0033]pellets10 are introduced into a patient by being carried on anelectromagnetic rod30 which is about 7 mm long. Aconductive wire34 is connected, on one end, to theelectromagnetic rod30 and at the other end, to anelectromagnetic power source50. To connect thepellet10 to theelectromagnetic rod30, apellet10 in the open position is placed on the end of therod30. At this time, current is sent via thewire34 to theelectromagnetic rod30 thereby charging therod30. Assuming thepellets10 are ferromagnetic, therod30 will be charged so that it emits an electromagnetic field that will attract thewings12 of theferromagnetic pellets10. In response to the electromagnetic field emitted by therod30, theferromagnetic wings12 are magnetically drawn onto the sides of the rod thereby placing thepellet10 in the closed configuration. Therod30, with the 10 pellet attached thereto, is then journalled into acatheter32. Thecatheter32, with therod30 andpellet10 therein, is then directed, via a femoral artery such as theaorta22, to a chamber of a heart24 of a patient. Although the chamber discussed in detail herein is the left ventricle20, the procedure is equally applicable to the right ventricle. Further, it is also possible to direct the catheter to the ventricles transthoracically, i.e., sending the catheter through the patient'schest wall26, rather than through a femoral artery.
• When in the left ventricle[0034]20, theferromagnetic pellet10 is placed adjacent theanterior wall25 of the left ventricle20. The pellet is firmly held in position against the endo-cardial wall25 by an external magnet positioned outside of the patient'schest wall26. Thesharp contact portion14 of thepellet10 is then forced into the myocardium of theanterior wall25 by an injection syringe which hydraulically forces therod30 with thepellet10 attached thereto into the myocardium of thewall25. Thepellet10 is inserted so that thecontact portion14 is about 10 mm into thewall25. As thepellet10, when in the open configuration has a length L of about 5 mm high, thepellet10 will be completely submerged in theanterior wall25 to a depth of approximately 5 mm.
• The current sent to the[0035]electromagnetic rod30 is then discontinued thereby removing the charge originally added to therod30. As a result of the loss in charge in therod30, thewings12 of thepellet10 will return to their biased open configuration. As the proximal ends18 of thewings12 are blunt and will, therefore, not easily cut through the tissue of theanterior wall25, thewings12 of thepellet10 will act as a barb maintaining theferromagnetic pellet10 in theanterior wall25. This process is repeated until a sufficient number offerromagnetic pellets10 are implanted in theanterior wall25 of the left ventricle20. Preferably, at least three or fourferromagnetic pellets10 will be implanted in theanterior wall25 and are distributed over an area of about 6-15 cm².
• After the[0036]ferromagnetic pellets10 are inserted in theanterior wall25, a similar number ofdiamagnetic pellets10 are inserted, using the same technique, in theposterior wall27. However, in inserting thediamagnetic pellets10 into theposterior wall27, the polarity of theelectromagnetic rod30 must be reversed so that it will be adapted to force thediamagnetic pellets10 into the closed configuration.
• After the[0037]pellets10 are inserted in theanterior wall25 and theposterior wall27, thecatheter32 is removed from the patient. At this time anelectromagnetic generator40 can be placed on the patient'schest wall26. By cyclically generating an electromagnetic field with theelectromagnetic generator40, thepellets10 in theanterior wall25 will be pushed away from theelectromagnetic generator40 while thepellets10 in theposterior chest wall27 will be pulled toward theelectromagnetic generator40. As thepellets10 in theanterior wall25 and theposterior wall27 approach each other, the result is an artificially assisted contraction of the left ventricle20.
• The electrical activity in the heart[0038]24, generated in response to the contraction of the left ventricle20, can be monitored with a conventional EKG monitor (not shown) having leads46 attached to the patient'schest wall26. Further, the EKG can output a waveform representative of the electrical activity which a doctor can interpret to determine whether the heart24 is functioning appropriately. Finally, the cyclical electromagnetic field generated by theelectromagnetic generator40 can be adjusted in response to the output of the EKG. The adjustment may be manual and/or automatic, if the EKG and theelectromagnetic generator40 are connected to a computer.
• Although the aforementioned describes preferred embodiments of the invention, the invention is not so restricted. It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed preferred embodiments of the present invention without departing from the scope or spirit of the invention. For example, although not preferable, it is possible to use one type of pellet (diamagnetic or ferromagnetic)[0039]10 implanted in both theanterior wall25 and theposterior wall27. However, this approach will require a secondelectromagnetic generator40, emitting the same cyclical electromagnetic field as the electromagnetic generator on thechest wall26, to be placed on the patient'sback wall28. Bothelectromagnetic generators40 would then push thepellets10 in theanterior wall25 toward thepellets10 in theposterior wall27. This method would not be preferred not because it uses twogenerators40 but also because thepellets10 in the ventricle may react to both generators thereby tending to remain stationary.
• Accordingly, it should be understood that the apparatus and method described herein are illustrative only and are not limiting upon the scope of the invention, which is indicated by the following claims. Accordingly, alternatives which would be obvious to one of ordinary skill in the art upon reading the teachings herein disclosed, are hereby within the scope of this invention.[0040]

Claims (15)

What is claimed is:

1. A method of inserting a magnetic pellet into a myocardial wall of a heart comprising the steps of:

supplying an electromagnetic field to the pellet attached to a distal end of an electromagnetic rod, wherein the rod is positioned within a delivery catheter, wherein the magnetic pellet has a plurality of spring-wings;

positioning the magnetic pellet at a target area on the myocardial wall;

inserting the pellet into the myocardial wall;

removing the electromagnetic field previously supplied to the pellet and thereby causing the spring-wings to open.

2. The method ofclaim 1, wherein the myocardial wall is in the heart's left ventricle.

3. The method ofclaim 1, wherein the myocardial wall is in the heart's right ventricle.

4. The method ofclaim 2, wherein the myocardial wall is a posterior wall or an anterior wall.

5. The method ofclaim 1, wherein the electromagnetic field is generated by an external electromagnetic generator, and wherein the external electromagnetic generator is electrically connected to a proximal end of the electromagnetic rod by a wire.

6. The method ofclaim 1, further comprising:

introducing the delivery catheter to the target area of the myocardial wall by sending the catheter through a femoral artery.

7. The method ofclaim 1, further comprising:

introducing the delivery catheter to the target area of the myocardial wall by transthoracically sending the catheter through a chest wall.

8. The method ofclaim 1, wherein the step of inserting the pellet into the myocardial wall is performed using an injection syringe positioned at a proximal end of the catheter.

9. A method of treating a patient's congestive heart failure comprising the steps of:

positioning a first plurality of spring-winged pellets in a myocardium of an anterior wall of a ventricle of the patient's heart;

positioning a second plurality of spring-winged pellets in a myocardium of a posterior wall of a ventricle of the patient's heart;

positioning an electromagnetic generator;

cyclically generating an electromagnetic field which magnetically interacts with the first and the second plurality of pellets;

magnetically pushing, in response to the cyclical electromagnetic field, the first plurality of pellets away from the electromagnetic generator; and

magnetically pulling, in response to the cyclical electromagnetic field, the second plurality of pellets toward the electromagnetic generator.

10. The method ofclaim 9, further comprising:

positioning an EKG monitor on the patient and generating a waveform of the heart's electrical activity; and

synchronizing the cyclical electromagnetic field cyclically to correspond to the heart's electrical activity.

11. A magnetic pellet adapted to be inserted into a patient's heart comprising:

a contact portion; and

a plurality of wings,

wherein each wing has a distal end portion hingedly connected to the contact portion, wherein each wing has a proximal end portion, and wherein the proximal end portions of the plurality of wings bend toward each other when an electromagnetic field is applied to the pellet.

12. The pellet ofclaim 11, wherein the pellet is formed of at least one ferromagnetic material.

13. The pellet ofclaim 11, wherein the pellet is formed of at least one diamagnetic material.

14. The pellet ofclaim 11, further comprising:

a polyurethane membrane covering the wings and contact portion.

15. The pellet ofclaim 14, wherein the membrane is vacuum-sealed onto the wings and contact portion.

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