US20080039727A1 - Ablative Cardiac Catheter System - Google Patents

Abstract

The present invention relates to a catheter system that can be used to treat atrial fibrillation and other cardiac arrhythmias by ablating cardiac tissue comprising a catheter, a guide wire, and an ultrasonically driven mechanical ablation probe. The catheter system may further comprise means of delivering cryogenic energy to the mechanical ablation probe, to a region of the catheter in close proximity to the mechanical ablation probe, and/or to another region of the catheter. The catheter may further comprise means of rotating and steering the mechanical ablation probe.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates to a catheter system than can be used to treat atrial fibrillation and other cardiac arrhythmias by ablating cardiac tissue.
• 2. Description of the Related Art:
• Accounting for one-third of the hospitalizations for cardiac arrhythmia, atrial fibrillation (AF) is the most common arrhythmia (abnormal beating of the heart) encountered in clinical practice. (ACC/AHA/ESC Guidelines for the Management of Patients With Atrial Fibrillation) AF is a specific type of arrhythmia in which an abnormal beating of the heart originates in one of the heart's two atrium. Increasing in prevalence, an estimated 2.2 million Americans suffer from AF. (ACC/AHA/ESC Guidelines for the Management of Patients With Atrial Fibrillation) Underlying one out of every six strokes, AF doubles the rate of morbidity compared to patients with normal sinus rhythm. (ACC/AHA/ESC Guidelines for the Management of Patients With Atrial Fibrillation) Further increasing the clinical severity, the presence of AF leads to functional and structural changes in the artial myocardium (cells responsible for the beating of the heart) that favors its maintenance. As such, AF is a serious disorder requiring medical intervention.
• Administering drugs that alter the electrical properties of atrial myocardium has been effective in treating less severe cases of AF. (Hurst's the heart, page 836) However, such drugs often lead to the creation of pro-arrhythmic conditions thereby resulting in the treatment of one type of arrhythmia only to create another. Due to the increased risk of stroke, it is advised that all patients with AF, despite the successfulness of drug therapy, be prescribed warfarin or other anticoagulants to inhibit the formation of blood clots. (Hurst's the heart, page 833) Besides being difficult to dose, warfarin has several complications associated with its long term use. Altering the metabolism of other drugs, warfarin is known to induce several adverse interactions with other medications commonly prescribed to elderly patients, who are at increased risk of developing AF.
• AF originates in regions of myocardium contracting, or beating, out of step with the rest of the heart. Heart cells contract in response to electrical stimulation. In a healthy heart, the electrical stimulation signaling contraction originates from the sinus node (the heart's natural pace maker) and spreads in an organized manner across the heart. In a heart plagued with AF, a region of myocardium elicits a mistimed contraction, or heart beat, on its own or in response to an electrical signal generated from somewhere other than the sinus node. Generating an electrical signal, the mistimed contraction spreads across the heart, inducing contractions in neighboring regions of the heart. Inducing the formation of scar tissue on the heart by ablating, cutting, or otherwise injuring tissue in regions in which AF originates has been shown to be affective in treating AF. The logic behind this treatment is to terminate AF by removing the heart cells responsible for its presence, while preserving healthy cells. Creating scar tissue barriers as to prevent the spread of electrical signals from mistimed contractions has also been shown to be effective in treating AF. (Hurst's the heart, page 838) Successful surgical intervention eliminates the need for continued warfarin treatment in most patients. (Hurst's the heart, page 839) Initially surgical treatment was reserved for patients undergoing additional cardiac surgery, such as valve repair or replacement. (Hurst's the heart, page 838) The high success rate and efficacy of surgical intervention in the treatment of AF has spurred the development of cardiac catheters capable of therapeutically ablating cardiac tissue without the need for open chest or open heart surgery.
• Heart surgery preformed by means of catheter involves, in it basic conception, the insertion of a catheter either into a patient's vein or chest cavity. The catheter is then advanced to the heart. When the catheter is inserted into a patient's vein, the catheter is advanced into one of the heart's four chambers. When the catheter in inserted into a patient's chest, the catheter is advanced to the outer walls of the patient's heart. After the catheter reaches the patient's heart the surgeon utilizes the catheter to ablate, damage or, kill cardiac tissue. The ideal catheter induced lesion is one that is created from the epicardium (outside) of the beating heart, is able to go through epicardial fat, is performed rapidly over variable lengths, is transmural, causes no collateral injury, and can be applied at any desired anatomic location. (Williams et al., 2004) Ablating cardiac tissue by heating the tissue to 50 degrees Celsius has become the preferred means of inducing lesions (Williams et al., 2004). Cardiac catheters employing a variety of thermal ablative energy sources have been developed, none of which are capable of inducing an ideal lesion.
• Catheters utilizing radio frequency as an ablative energy source, the current gold standard, are incapable of creating an ideal lesion. (Cummings et al., 2005) In particular, radio frequency catheters have a difficult time creating ablations through the epicardial fat surrounding the heart. Furthermore, inducing deep lesions with radio frequency is not possible without inflicting collateral damage from surface burning and steam popping. (Cummings et al., 2005) Steam popping is the phenomenon in which cells become heated to such a point their internal fluids begin to boil, producing steam that bursts the cell. Simultaneously cooling the site of radio frequency administration reduces the incidence of surface burns but does not reduce the risk of steam popping. (Cummings et al., 2005) In an effort to overcome the shortcomings of radio frequency induced lesions, catheters employing novel energy sources have been developed.
• In hopes that microwaves would provide sufficiently deep lesions, catheters employing microwaves as an ablative energy source have been developed. Because the penetration of microwaves into tissue has a steep exponential decline, it has been found necessary to bring the catheter into close contact with the tissue in order to induce deep lesions. (Cummings et al., 2005) Furthermore, the exponential decline in energy with tissue depth requires exposing the tissue to high levels of energy when inducing deep lesions. Consequently, surface burning and steam popping is likely during the induction of deep lesions with a microwave catheter. Furthermore, fat continues to be a significant barrier. (Williams et al., 2004) Lasers have also been applied as an ablative energy source within catheters. Although high powered lasers carry a high risk of crater formation at the site of application, low energy lasers produce lesions with a depth related to the duration of application. (Cummings et al., 2005) Therefore, the ideal rapid induction of a deep lesion is not possible with laser catheters without the risk of crater formation and collateral damage.
• Capable of penetrating fat and inducing fasts lesion at specific depths when focused, high intensity ultrasound has been predicted to be an advantageous source of ablative energy in catheters. (Williams et al., 2004) However, properly focusing ultrasound energy requires exact knowledge as to the depth of the lesion and the position of the catheter, which may not be possible in a closed heart or closed chest procedure. Furthermore, high intensity ultrasound is capable of inducing internal cavitations resulting in apoptosis (a delayed form of cellular death) as it passes through cells on its way to the desired location of the lesion. Consequently, ultrasound induced lesions, though fast, are not free from the complications of collateral damage. Furthermore, collateral damage may not become apparent until sometime after the procedure.
• Besides the specific complications mentioned for the currently available ablative heat energy sources they, as a whole, suffer from shared problems of heat sink and clot formation. With respect to clot formation, the heat produced at the site of energy release from the catheter can result in the formation of blood clots on the catheter. If such bloods clots dislodge when the catheter is withdrawn, especially when the catheter is used to induce lesion from within the heart, it can result in serious complications including stroke. The other shared shortcoming, heat sink, can exacerbate the occurrence of clot formation. The continuous blood flow through and around the heart creates a natural heat sink cooling the site of energy application as well as the location of the desired lesion. Consequently, more energy must be emitted from the catheter to heat the target myocardium to 50 degrees Celsius. Making the catheter hotter, unfortunately, increases the risk of clot formation on and around the catheter.
• An alternative to ablation by heating is the practice of ablating tissue by freezing. Severe cold, also know cryogenic energy, as an ablative energy source has the advantages of avoiding clot formation. (Williams et al., 2004) Another advantage of catheters employing cryogenic energy is the ability to temporary paralyze regions of myocardium tissue as to test the benefit of a planned lesion. When a region of tissue is paralyzed by freezing it can no longer initiate an arrhythmia. If paralyzing a region of the heart completely or partial restores a normal heart beat, the surgeon knows she has her catheter aimed at the right spot. However, cryoablative catheters are not without their limitations. In particular, cyroadhesion (the freezing of the catheter to cardiac tissue) though capable of stabilizing the catheter makes it difficult for the surgeon to move the catheter during the ablative procedure. Furthermore, requiring multiple applications for the induction of a therapeutic lesion cryoablative catheters are not capable of rapidly inducing lesions.
• Therefore, a need exists for a cardiac catheter that is capable of rapidly inducing lesions of varying depth through epicardial fat without causing excessive collateral damage.
SUMMARY OF THE INVENTION
• The present invention relates to an ablative cardiac catheter system that can be used to ablate cardiac tissue comprising a catheter, a guide wire, and an ultrasonically driven mechanical ablation probe. The catheter may further comprise means of delivering cryogenic energy to the mechanical ablation probe, to a region of the catheter in close proximity to the mechanical ablation probe, and/or to another region of the catheter. The catheter may further comprise means of rotating and steering the mechanical ablation probe. The catheter may also comprise a reservoir and/or lumen from which a drug can be administered. The ablation probe may also be coated with a drug or other pharmacological compound. Driving the ablation probe with ultrasonic energy will liberate the drug coating from the probe and embed it within the target tissue.
• The catheter system contains at its distal end an ultrasonically driven mechanical ablation probe possessing cutting surfaces. When driven by ultrasonic energy when in contact with tissue, the probe mechanically ablates the target tissue. Mechanical ablation may be utilized to cut away and penetrate epicardial fat, thereby exposing the underlying myocardium. The exposed myocardium may then be subjected to cryoablation, ultrasonic ablation, mechanical ablation, and/or any combination thereof.
• A handle at the proximal end contains control means for steering and/or rotating that ablation probe. Between the handle and ablation probe is a catheter composed of a biologically compatible polymer. The catheter may contain lumens permitting the flow of a cooling material as to enable cooling of the ablation probe. The catheter may also contain a drug lumen and/or drug reservoir permitting the administration of a drug to internal locations of the patient's body. Running the length of the catheter, a guide wire connects the ablation probe to the handle. The guide wire may contain lumens permitting the flow of a cooling material. The guide wire may also carry electrical leads to the ablation probe. Additionally, the guide wire may also house means of deflecting or steering the ablative the probe.
• A catheter system embodying the present invention may be used in the surgical treatment of cardiac arrhythmias by providing a means to mechanically, ultrasonically, and/or cryogenically ablate myocardial tissue. As such, a surgeon utilizing a catheter system embodying the present invention will be able to select the appropriate ablative means or combination of ablative means best suited for the patient's particular pathology and the type of lesion the surgeon wishes to induce. It should be understood that the term “surgeon” references all potential users of the present invention and does not limit the use of the present invention to any particular healthcare or medical professional or healthcare or medical professionals in general.
• Driving the mechanical ablation probe with low frequency ultrasound enables the surgeon to quickly induce surface lesions of various depths. Adjusting the pulse frequency and duration of the driving ultrasound gives the surgeon control over lesion depth. This may prove advantageous when the surgeon wishes to induce a lesion at a specific location with minimal collateral injury, such as during AV nodal modification.
• Combining ultrasonic energy with cryogenic energy enables the surgeon to cryoablate tissue without the fear of the ablation probe adhering to the tissue being ablated. As such, the surgeon will be able to easily move the probe during ablation. The probes mobility during cryoablation allows the surgeon to create linear lesions or isolating lesions in vessel walls. Thus, combining ultrasonic and cryogenic energy during ablation gives the surgeon greater control over the lesion induced. Furthermore, it has been hypothesized the administration of low frequency ultrasound and cryoablation induces the release of several healing factors from the targeted tissue. Therefore, ultrasonically vibrating the ablation probe during cryoablation will improve the mobility of the ablation probe and possibly induce healing.
• Dually administering ultrasonic and cryogenic energy may protect surface tissue during the administration of deep lesion, thereby limiting collateral damage. During the cryogenic induction of a deep lesion the co-administration of ultrasonic energy will warm the surface tissue preventing it from freezing. Likewise administering cryogenic energy during the induction of a deep lesion with ultrasonic energy will cool surface tissue protecting it from ablative cavitation by reducing molecular movement.
• A catheter system embodying the present invention will also enable the surgeon to deliver various drugs to the location of the lesion and/or other locations. Combining drug delivery with the application of ultrasound may assist drug delivery and penetration into target tissue. Delivering an antithrombolytic during ablation may serve to reduce the likelihood of clot formation, especially during mechanical ablation. The surgeon may also choose to expedite healing by delivering various healing and/or growth factors to the site of ablation.
• One aspect of the present invention is to provide a means of combining ultrasound, cryogenic energy, and/or mechanical ablation in the induction of therapeutic lesions.
• Another aspect of the present invention is to provide a means of cryoablation without cryoadhesion.
• Another aspect of the present invention is to provide a means of dispatching epicardial fat as to expose the underlying myocardium.
• Another aspect of the present invention is to provide for a means of combining the induction the therapeutic lesions with drug delivery.
• These and other aspects of the invention will become more apparent from the written descriptions and figures below.
BRIEF DESCRIPTION OF THE DRAWINGS
• The present Invention will be shown and described with reference to the drawings of preferred embodiments and clearly understood in details.
• FIG. 1 depicts the entire catheter system of the present invention.
• FIG. 2 is an exposed view of the ultrasonically driven mechanical ablation probe deployed from tip of the catheter system depicted inFIG. 1.
• FIG. 3 depicts cross-sectional views of the proximal end of one embodiment of the present invention.
• FIG. 4 depicts a cross-sectional view of the body of the catheter system depicted inFIGS. 1 and 3.
• FIG. 5 depicts cross-sectional views of the proximal end of one embodiment of the present invention comprising a guide wire with two internal lumens.
• FIG. 6 depicts a cross-sectional view of the body of the catheter system depicted inFIG. 5.
• FIG. 7 depicts a system view of the embodiment of the present invention depicted inFIGS. 6 and 5.
• FIG. 8 depicts alternative cutting surfaces.
• FIG. 9 depicts different transducer configurations that may be utilized to drive the ablation probe.
DETAILED DESCRIPTION OF THE INVENTION
• The present invention is an ablative cardiac catheter system that can be used to treat artrial fibrillation and other arrhythmias. Preferred embodiments of the present invention in the context of an apparatus and methods are illustrated in the figures and described in detail below.
• FIG. 1 depicts the entire catheter system of the present invention. Ahandle5 at the proximal end of the catheter system contains control means4 for steering and/or rotating an ablation probe (not visible) enclosed within the catheter system. Exemplar control means have been described in U.S. Pat. No. 4,582,181 to Samson and U.S. Pat. No. 4,960,134 to Webster and are incorporated herein by reference. When rotated the ablation probe moves in a circular motion similar to the manner in which the hands of a clock move about its face. Rotation of the ablation probe can also be accomplished by the surgeon by turninghandle5 with his wrist as if he were using a screw driver. Between thehandle5 and the ablation probe (not visible) is aguide wire7, providing rigidity to the catheter system.Guide wire7 also carrieselectrical leads6 down the catheter system to the ablation probe held within. Transmitting power fromgenerator1, the electrical leads energize and drive the ablation probe in a manner described in detail below. Surroundingguide wire7 iscatheter8, comprising two internal lumens, composed of a biologically compatible polymer. Though such polymers are familiar to those skilled in the art, they can simply be understood as polymers, or plastics, that will not normally irritate or harm the body.Co-pending application 11/454,018, Method and Apparatus for Treating Vascular Obstructions, filed Jun. 15, 2006, discloses various exemplar configurations of catheters that may be used with the present invention and are incorporated herein by reference. The internal lumens ofcatheter8 permit the flow of a cooling material through the catheter system as to cool the ablation probe. Connected to the proximal end of the internal lumens ofcatheter8 are cryogenic feed andexhaust tubing2. Thecryogenic tubing2 allows a cooling material to be delivered to the internal lumens ofcatheter8 from a cryogenic storage andretrieval unit3 and then returned to the storage andretrieval unit3 after exitingcatheter8. Cryogenic storage and retrieval may alternatively be accomplished by the simultaneous use of separate storage and retrieval units. The storage and retrieval unit may also permit the recycling of the employed cooling material as to reduce operation costs. In order to the prevent the catheter system from becoming rigid and inflexible as cryogenic material flows throughcatheter8, the catheter, or a portion thereof, may be wrap with a wire conducting an electrical current. The resistance within the wire to the flow of electricity generates heat that warms the catheter system, thereby keeping the system flexible. Alternatively, the warming wire may be wrapped aroundguide wire7.
• In keeping withFIG. 1, the catheter system contains at its distal end a deployable ultrasonically driven mechanical ablation probe enclosed withintip9 formed by thecatheter8. Firmly pullingcatheter8 towardshandle5, while holdinghandle5 stationary, exposes the ablation probe. As to facilitate penetration oftip9 by the ablation probe,tip9 may possess a single ormultiple slits10. Slit(s)10 may completely or partially penetratetip9. Conversely, firmly pullinghandle5 away from the patient while holdingcatheter8 stationary returns the ablation probe to the inside ofcatheter8. Advancing the catheter system into and through the patient's body with the ablation probe retracted within the catheter protects the patient's internal tissues from damage by the ablation probe. When the ablation probe has been advanced to the desired lesion location, the surgeon may retract the catheter, exposing the ablation probe. The surgeon may then mechanically induce a lesion by driving the ablation probe with ultrasound. Alternatively, the surgeon may not expose the ablation probe by retractingcatheter8 but rather induce a lesion with low frequency ultrasound and/or cryogenic energy.
• Depicted inFIG. 2 is an exposed view of the ultrasonically driven mechanical ablation probe deployed fromtip9 depicted inFIG. 1. Theablation probe11 comprises anablative tip19 possessing a cuttingsurface12. Theablation probe11 may comprise anultrasonic transducer17 at the proximal end of theablative tip19. Theultrasonic transducer17 generates ultrasonic energy capable of driving theablation probe11. The ultrasonic transducer may comprise a single piezoceramic disc18. Though well known to those skilled in the art, a piezo ceramic disc can be simply understood as a ceramic disk that expands and contracts when exposed to an alternating voltage. Alternatively, thetransducer17 may also comprise a stack of piezoceramic disc18 arranged in a manner similar to that of a roll of coins. Running alongguide wire7,electrical leads6 goes to electrodes (not shown) to energizetransducer17 with power supplied by a generator (1 inFIG. 1) thereby driving theablation probe11. Attached to the proximal end oftransducer17, back drive16 stabilizesablation probe11 whenablation probe11 is driven by ultrasound generated bytransducer17.Guide wire7 attached to the proximal end ofback drive16 comprises asemi-circular channel20, running its length, partially envelopingcontrol wire21. Extending down thechannel20 to handle5 depicted inFIG. 1,control wire21 deflects or steersablation probe11 in response to changes in tension about its length induced by manipulation of control means4 depicted inFIG. 1. Alternatively,guide wire7 may completely envelopcontrol wire21 such thatchannel20 forms a lumen aroundcontrol wire21.
• Incorporating threading on a portion of the ablation probe along with corresponding threading on the internal surface of the catheter tip would facilitate a smooth deployment of the ablation probe from the catheter tip. In such an embodiment, the surgeon would advance the ablation probe from the catheter tip be rotating the guide wire and the attached ablation probe. Rotating the guide wire in the opposite direction would retract the ablation back into the catheter tip.
• The ultrasound transducer responsible for driving the ablation probe need not be incorporated within the ablation probe. Instead, the transducer may be in communication with the guide wire attached to the ablation probe, driving the ablation probe through said communication. In such an embodiment, the transducer may be located anywhere within the catheter system of the present invention, including, but not limited to, the handle. The transducer may also be located elsewhere within the catheter system of the present invention, provided the transducer is in direct or indirect communication with the ablation probe.
• Incorporating a mapping electrode placed at or near the tip, distal end, of the catheter system would assist the surgeon in locating specific sites arrhythmia. Alternatively, the mapping electrode may be located near or attached to the ablation probe. A mapping electrode would enable the surgeon to detect the electrical activity of the cells near the electrode. The surgeon could use the detected electrical activity to determine if the cells near the electrode are contributing to the arrhythmia. Furthermore, the surgeon may administer cryogenic energy to a region of myocardium suspected to be contributing to the patient's arrhythmia as to paralyze the tissue. If paralyzing the tissue completely or partially corrects the patient's arrhythmia, the surgeon may then ablate the tissue with the ablation probe.
• Incorporating a temperature sensor placed at or neat the distal end of catheter system would enable the surgeon to monitor the temperature at the site of the ablation. Alternatively, the temperature sensor may be located near or attached to the ablation probe. Monitoring the temperature near or at the site of the ablation with the temperature sensor would assist the surgeon in avoiding burning and/or inflicting other undesirable damage or injury. When the temperature of the tissue being ablated reaches or approaches an undesirable level, the surgeon could stop the ablation and allow the tissue to return to a safer temperature. The surgeon may also adjust the ultrasound parameters as to slow the change in temperature. If the ablative procedure being preformed involves cryoablation or the administration of cryogenic energy, the surgeon may adjust the flow of cryogenic material through the catheter system as to slow the change in temperature.
• FIG. 3 depicts cross-sectional views of proximal end of one embodiment of the present invention.FIG. 3adepicts a cross-sectional view with theablation probe11 extended.FIG. 3bdepicts a cross-sectional view withablation probe11 retracted.Catheter8 comprises an internalcryogenic intake lumen13 and an exhaust lumen (obscured by intake lumen13) connected by port(s)14. The flow of a cooling material from the proximal to the distal end ofcatheter8 through theintake lumen13, across port(s)14, and then back to the proximal end ofcatheter8 through the exhaust lumen cools thecatheter tip9. The junction between the internal lumens ofcatheter8 may be simple a simple port(s), as depicted inFIG. 3, or alternatively a chamber. The cryogenic material may flow adjacent to or in close proximity to theablation probe11 as to cool the probe. Incorporating a flow regulator, as to permit the surgeon to regulate or adjust the flow rate of cryogenic material throughcatheter8 would allow the amount of cooling to be controlled by the surgeon.
• In keeping withFIG. 3,catheter8 may be retracted with a firm pull towards the handle (5 inFIG. 1), while the handle (5 inFIG. 1) is keep stationary, as to exposeablation probe11 entirely or the ablation probe's cutting surface(s)12. The catheter system of the present invention may possess aclosed tip9, as depicted inFIG. 3b, with a single ormultiple slits10, completely envelopingablation probe11. The slit(s)10 may completely or partially penetratecatheter tip9. When the catheter is retractedablation probe11 penetratestip9. Whenablation probe11 is retracted by a firm pull on the handle (5 inFIG. 1) while holding thecatheter8 stationary theablation probe11 is returned to the inside of thecatheter tip9. Whentip9 has been advanced to the desired lesion location, the surgeon may retractcatheter8, exposing cutting surface(s)12. The surgeon may then mechanically induce a lesion by drivingablation probe11 with ultrasound. Alternatively, the surgeon may not expose cutting surface(s)12 but rather induce a lesion with low frequency ultrasound and/or cryogenic energy.
• FIG. 4 depicts a cross-sectional view of the body of the catheter system depicted inFIGS. 1 and 3.Catheter8 comprises acryogenic intake lumen13 andexhaust lumen15, collectively envelopingguide wire7 andcontrol wire21.Guide wire7 further comprises asemi-circular channel20 running its length that partially envelopscontrol wire21. Alternatively,guide wire7 may completely envelopcontrol wire21 such thatchannel20 forms a lumen aroundcontrol wire21.
• FIG. 5 depicts cross-sectional views of the proximal end of one embodiment of the present invention comprising aguide wire7 with twointernal lumens22 and23.FIG. 5a depicts a cross-sectional view of the alternative embodiment withablation probe11 extended.FIG. 5bdepicts a cross-sectional view of the alternative embodiment withablation probe11 retracted.Guide wire7 comprises an internalcryogenic intake lumen22 andexhaust lumen23 running the length ofguide wire7 and opening intoexpansion chamber24 withinablative tip19. The flow of a cooling material from the proximal to the distal end ofguide wire7 through theintake lumen22, intoexpansion chamber24, and then back to the proximal end ofguide wire7 through theexhaust lumen23 coolsablation probe11.Expansion chamber24 may be located withinablative tip19, as depicted inFIG. 5. Alternatively,expansion chamber24 may be located withintransducer17 and could, but need not, extend intoablative tip19. Incorporating a flow regulator, as to permit the surgeon to regulate or adjust the flow rate of cryogenic material throughguide wire7 would allow the amount of cooling to be controlled by the surgeon.
• FIG. 6 depicts a cross-sectional view of the body of the catheter system depicted inFIG. 5.Catheter8 envelopsguide wire7 andcontrol wire21.Guide wire7 comprises acryogenic intake lumen22 andexhaust lumen23.Guide wire7 further comprises asemi-circular channel20 running its length that partially envelopscontrol wire21. Alternatively,guide wire7 may completely envelopcontrol wire21 such thatchannel20 forms a lumen aroundcontrol wire21.
• FIG. 7 depicts a system view of the embodiment of the present invention depicted inFIGS. 6 and 5. Ahandle5 at the proximal end of the catheter system contains control means4 for steering and/or rotating the ablation probe (not visible). Between thehandle5 and ablation probe (not visible) is aguide wire7 providing rigidity to the catheter system.Guide wire7 comprises two internal lumens. The internal lumens ofguide wire7 permit the flow of a cooling material throughguide wire7 as to cool the ablation probe enclosed withintip9. Connected to the proximal ends of the internal lumens ofguide wire7 are cryogenic feed andexhaust tubing2; permitting cooling material to be delivered to and collected from the internal lumens ofguide wire7 by cryogenic storage andretrieval unit3.Guide wire7 also carrieselectrical leads6 down the catheter system to the ablation probe held within. Transmitting power fromgenerator1,electrical leads6 energize and drive the ablation probe. Surroundingguide wire7 iscatheter8 composed of a biologically compatible polymer.
• In keeping withFIG. 7, the catheter system contains at its distal end a deployable ultrasonically driven mechanical ablation probe enclosed withintip9. Firmly pullingcatheter8 towardshandle5, while holdinghandle5 stationary, exposes the ablation probe. As to facilitate penetration oftip9 by the ablation probe,tip9 may possess a single ormultiple slits10. Slit(s)10 may completely or partially penetratetip9. Conversely, firmly pullinghandle5 away from the patient while holdingcatheter8 stationary returns the ablation probe to the inside ofcatheter8.
• “Ultrasonically driven” refers to causing the ablation probe to move by applying ultrasonic energy to the probe via a driving transducer in direct or indirect contract with the probe. Applying ultrasonic energy may cause a vibrating or oscillating movement of the probe. The ablation probe, however, may move in other manners when driven by ultrasound. When in motion and in direct contract with tissue, the probe mechanically ablates the tissue. Mechanical ablation refers to injuring tissue by cutting, gouging, tearing, ripping, scratching, scoring, or other means of physically damaging tissue.
• The ablation probe is driven by ultrasound with a frequency between 20 kHz and 20 MHz. The recommended frequency of the driving ultrasound is 30 to 40 kHz. The driving ultrasound has an intensity at least 0.1 Watts per centimeter squared. Pulse duration and treatment time are dependent upon the depth and type of lesion the surgeon wishes to induce.
• Pulsing the driving ultrasound by repeatedly turning the driving ultrasound transducer on and off gives the user control over lesion depth. Incorporating an ultrasound controller permits the user to control, regulate, or adjust, the pulse duration and pulse frequency of the driving ultrasound. Pulse duration refers to length of time the ultrasound transducer is on, generating ultrasound. Pulse frequency refers to how often the ultrasound transducer turns on during a period of time. Adjusting the pulse frequency and duration enables the surgeon to control the depth of the lesion inflicted by theablation probe11 depicted inFIG. 2 andFIG. 3.
• When the ablation probe (11 inFIG. 3 andFIG. 2) has been advanced to the desired lesion location, the surgeon may retract the catheter (8 inFIG. 3,FIG. 2 andFIG. 1), exposing the ablative tip's cutting surface(s) (12 inFIG. 3 andFIG. 2). The surgeon may then mechanically induce a lesion by driving the ablation probe (11 inFIG. 3 andFIG. 2) with ultrasound. Alternatively, the surgeon may not expose the ablation probe's cutting surface(s) (12 inFIG. 3 andFIG. 2) but rather activate the flow of cryogenic material through catheter (8 inFIG. 3,FIG. 2 andFIG. 1) as to induce a lesion by means of cryoablation. If the surgeon wishes to induce a continuous lesion across a segment of cardiac tissue the surgeon may activate the ultrasound transducer (17 inFIG. 3 andFIG. 2) to prevent cryoadhesion of catheter tip (9 inFIG. 3,FIG. 2 andFIG. 1) to the target tissue. Activating the ultrasound transducer (17 inFIG. 3 andFIG. 2) during cryoablation enables the surgeon to warm surface tissue at the site of ablation, thereby protecting surface tissue from ablation or injury. Likewise, activating the flow of cryogenic material through the catheter while ultrasonically inducing a lesion enables the surgeon to cool surface tissue at the site of the ablation, thereby protecting it from ablation or injury.
• The cutting surface(s) (12 inFIG. 3 andFIG. 2) of the ablation probe (11 inFIG. 3 andFIG. 2) may be constructed in various configurations, as depicted inFIG. 8. The cutting surface, depicted inFIG. 8a, comprises athin band25 spiraling aroundablative tip19 similar to the threads of screw. Alternatively, the cutting surface, as depicted inFIG. 8b, may comprise a thin band(s)26 encirclingablative tip19. The cutting surface may also comprise a thin band(s) extending from the tip, proximal end, of the ablative tip to its base, distal end. The cutting surface may also comprise asmall particle27 attached toablative tip19, conceptually similar to a grain of grit on a piece of sand paper, as depicted inFIG. 8c.FIG. 8cdepictsablative tip19 completely covered by such cutting surfaces27. The cutting surface, as depicted in cross-sectional view inFIG. 8d, may comprise a small protrusion(s) extending from the side or distal end ofablative tip19. The ablation probes depicted inFIG. 8 may be constructed by attaching or affixing the cutting surfaces to the ablative tip. Alternatively, the ablation probes depicted inFIG. 8 may be constructed such that the cutting surfaces are extensions of, integral with, the ablative tip.
• FIG. 9 depicts different transducer configurations that may be utilized to drive the ablation probe. The transducer may be comprised of a single piezo ceramic disc. Alternatively, transducer may be comprised of a collection of piezo ceramic disc as depicted inFIG. 9. The transducer may be constructed from cylindrical piezoceramic disc29 stacked upon one another in a manner resembling a roll of coins, as depicted inFIG. 9a. Such an arrangement imparts an axial or longitudinal displacement of the driven ablation probe (11 inFIG. 3 andFIG. 2) when energized. Alternatively, the transducer may be constructed from a pair of half cylindrical piezoceramic discs30 combined to form a cylinder, as depicted inFIG. 9b. Such an arrangement imparts a circumferential displacement of the drivenablation probe11 inFIG. 3 andFIG. 2) when energized. The transducer may be configured from a combination of cylindrical piezoceramic discs29 and half cylindrical piezoceramic discs30, as depicted inFIG. 9c. Such a combination arrangement imparts an axial and circumferential displacement of the drivenablation probe11 inFIG. 3 andFIG. 2) when energized.
• The ablative catheter may also contain a drug lumen through which a drug solution or other fluid or composition may be introduced into the patient's body through the catheter Ultrasonically driving the ablation probe, while simultaneous delivering drug through the catheter by way of the drug lumen, may be utilized by the surgeon to facilitate drug flow through and release from the catheter as well as drug penetration into target tissue.
• The ablative catheter may also contain a drug reservoir at its distal end. The drug reservoir may surround the ablation probe. Alternatively, the drug reservoir may be located above, proximal, to the ablation probe. When located above the ablation probe, the drug reservoir may contain slits at its base. The slits may completely or partially penetrate the base of the drug reservoir. Retracting the catheter causes the ablation probe to penetrate the base of the drug reservoir and eventually the tip of the catheter. Traveling through the drug reservoir the ablation probe is coated with drug. Suspending the drug within a viscous or gel solution may offer better coating of the ablation probe as it travels through the drug reservoir. Ultrasonically driving the ablation probe will cause the drug solution clinging to the ablation probe to be liberated and embedded in tissue at and surrounding the site of the lesion. Similarly, ultrasonically driving the ablation probe while the probe is retracted may cause release of drug from the drug reservoir.
• Alternatively, drug delivery during treatment may be accomplished by first coating the ablation probe with a pharmacological compound. As in the above mentioned embodiment, ultrasonically driving the ablation probe will liberate, or shake lose, the drug compound coating; dispersing it into the treated tissue.
• Although specific embodiments and methods of use have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments and methods shown. It is to be understood that the above description is intended to be illustrative and not restrictive. Combinations of the above embodiments and other embodiments as well as combinations of the above methods of use and other methods of use will be apparent to those having skill in the art upon review of the present disclosure. The scope of the present invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims (46)

1. An ablation catheter system comprising:

a. a catheter;

b. a guide wire within said catheter and running the length of said catheter;

c. an ultrasonically driven mechanical ablation probe at the distal end of said guide wire;

2. The ablation catheter system ofclaim 1, further comprising a handle at the proximal end of said guide wire.

3. The ablation catheter system ofclaim 1, further comprising control means allowing a surgeon to steer said ablation probe.

4. The ablation catheter system ofclaim 1, further comprising control means allowing a surgeon to rotate said ablation probe.

5. The ablation catheter system ofclaim 1, wherein said catheter is retractable as to allow said ablation probe to be completely and/or partially exposed.

6. The ablation catheter system ofclaim 1, wherein said catheter has a closed tip enveloping said ablation probe.

7. The ablation catheter system ofclaim 6, wherein said closed tip has a slit or a plurality of slits completely and/or partially penetrating said closed tip.

8. The ablation catheter system ofclaim 1, further comprising a driving ultrasonic transducer in communication with said guide wire.

9. The ablation catheter system ofclaim 1, further comprising an ultrasound control means permitting the user to regulate, control, and/or adjust pulse duration and/or pulse frequency.

10. The ablation catheter system ofclaim 1, wherein said catheter comprises:

a. a first lumen extending from or a point near the catheter's distal end to a point at or near the catheter's proximal end;

b. a second lumen extending from or a point near the catheter's distal end to a point at or near the catheter's proximal end;

c. an inlet at or near the proximal end of said first lumen;

d. an outlet at or near the proximal end of said second lumen; and

e. a junction between said first and second lumen permitting the flow of fluid and/or gas from said first lumen to said second lumen.

11. The ablation catheter system ofclaim 10, wherein said junction between said first lumen and second lumen comprises a chamber.

12. The ablation catheter system ofclaim 10, wherein said junction between said first lumen and said second lumen comprises a port or plurality of ports connecting said lumens.

13. The ablation catheter system ofclaim 10, further comprising a source of cryogenic material connected to said first lumen.

14. The ablation catheter system ofclaim 13, wherein said source of cryogenic material is connected to said first lumen by a hose.

15. The ablation catheter ofclaim 10, further comprising a collection unit connected to said second lumen.

16. The ablation catheter ofclaim 15, wherein said collection unit is connected to said second lumen by a hose.

17. The ablation catheter ofclaim 10, further comprising a flow regulator permitting a surgeon to regulate and/or adjust the flow of a cryogenic material through said catheter.

18. The ablation catheter system ofclaim 1, wherein said guide wire comprises:

a. a first lumen extending from or a point near the guide wire's distal end to a point at or near the guide wire's proximal end;

b. a second lumen extending from or a point near the guide wire's distal end to a point at or near the guide wire's proximal end;

c. an inlet at or near the proximal end of said first lumen;

d. an outlet at or near the proximal end of said second lumen; and

e. a junction between said first and second lumen permitting the flow of fluid and/or gas from said first lumen to said second lumen.

19. The ablation catheter system ofclaim 18, wherein said junction between said first lumen and second lumen comprises a chamber within the guide wire's distal end.

20. The ablation catheter system ofclaim 18, wherein said junction between said first lumen and second lumen comprises a channel extending into the ablation probe.

21. The ablation catheter system ofclaim 18, further comprising a source of cryogenic material connected to said first lumen.

22. The ablation catheter system ofclaim 21, wherein said source of cryogenic material is connected to said first lumen by a hose.

23. The ablation catheter system ofclaim 18, further comprising a collection unit connected to said second lumen.

24. The ablation catheter system ofclaim 23, wherein said collection unit is connected to said second lumen by a hose.

25. The ablation catheter system ofclaim 18, further comprising a flow regulator permitting a surgeon to regulate and/or adjust the flow of a cryogenic material through said guide wire.

26. The ablation catheter system ofclaim 1, wherein said ablation probe is driven by ultrasound with a frequency ranging from approximately 20 kHz to approximately 20 MHz.

27. The ablation catheter system ofclaim 1, wherein said ablation probe is driven by ultrasound with a preferred frequency ranging from approximately 20 kHz to approximately 50 kHz.

28. The ablation catheter system ofclaim 1, wherein said ablation probe is driven by ultrasound with a most preferred frequency of approximately 30 kHz.

29. An ablation probe comprising an ablative tip possessing a single or plurality of cutting surfaces, wherein said ablation probe is ultrasonically driven.

30. The ablation probe ofclaim 29, wherein said cutting surface comprises a thin band spiraling around said ablative tip beginning at or near the distal end of the ablation probe and extending to or near the proximal end of said ablative tip.

31. The ablation probe ofclaim 29, wherein said cutting surface comprises a thin band encircling said ablative tip.

32. The ablation probe ofclaim 29, wherein said cutting surface comprises a small particle attached to the side or distal end of said ablative tip.

33. The ablation probe ofclaim 29, wherein said cutting surface comprises a small protrusion extending from the side or distal end of said ablative tip.

34. The ablation probe ofclaim 29, wherein said cutting surface comprises a thin band extending from or a point near the distal end of the ablation probe to or a point near the proximal end of said ablative tip.

35. The ablation probe ofclaim 29, further comprising an ultrasound transducer at the proximal end of said ablative tip.

36. The ablation probe ofclaim 35, further comprising a back drive at the proximal end of said ultrasound transducer.

37. The ablation probe ofclaim 36, further comprising a chamber wherein said chamber extends from the proximal end of said back drive into or through said back drive.

38. The ablation probe ofclaim 35, further comprising a chamber wherein said chamber extends from the proximal end of said ultrasonic transducer into or through said ultrasonic transducer.

39. The ablation probe ofclaim 29, further comprising a chamber wherein said chamber extends from the proximal end of said ablative tip into or through said ablative tip.

40. The ablation probe ofclaim 29, further comprising a coating of a pharmacological compound or mixture of pharmacological compounds over at least a portion of said ablative tip.

41. A driving ultrasound transducer comprising a singular or plurality of piezo ceramic discs wherein said transducer drives a mechanical ablation probe.

42. The driving ultrasound transducer ofclaim 41, wherein said ultrasonic transducer comprises a piezo ceramic disc.

43. The driving ultrasound transducer ofclaim 41, wherein said ultrasonic transducer comprises a stack of piezo ceramic disc.

44. The driving ultrasound transducer ofclaim 41, wherein said ultrasonic transducer comprises a pair or plurality of pairs of half cylindrical piezo ceramic discs aligned to form a cylinder.

45. The driving ultrasound transducer ofclaim 41, wherein said ultrasonic transducer comprises a combination of cylindrical peizo ceramic discs and pairs of half cylindrical piezo ceramic discs aligned to a form a cylinder.

46. The driving ultrasound transducer ofclaim 41, further comprising a chamber wherein said chamber extends from the proximal end of said ultrasonic transducer into or through said ultrasonic transducer.

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