WO1997013547A1

WO1997013547A1 - Device for treating cardiac arrhythmia by heating or cooling

Info

Publication number: WO1997013547A1
Application number: PCT/US1996/016273
Authority: WO
Inventors: Stanislao F. Obino; Paul J. Buscemi
Original assignee: Pharmatarget, Inc.
Priority date: 1995-10-12
Filing date: 1996-10-11
Publication date: 1997-04-17
Also published as: AU7438396A

Abstract

A device for the treatment of cardiac arrhythmias (7) which detects the occurrence of an arrhythmia and modifies the temperature of endocardial tissue without causing permanent damage to the tissue site. The device contains a thermal catheter (2) inserted into the heart (1) comprising a sensor electrode (5, 6) and a means for adjusting temperature at the distal end of the catheter. The thermal catheter may either cool or heat the tissue and the device may have a means for drug infusion.

Description

DEVICE FOR TREATING CARDIAC ARRHYTHMIA BY HEATING OR COOLING

FIELD OF THE INVENTION

The present invention relates generally to the field of implantable medical devices for heart rhythm management. In particular, the invention pertains to both apparatus and methods for treating cardiac arrhythmias.

BACKGROUND OF THE INVENTION

Many cardiac arrhythmias arise from aberrant localized patterns of electrical conduction within the heart tissue. Tissue sites associated with myocardial infarction and anatomic accessory pathways may each create or participate in so-called re-entrant circuits which may provoke and sustain tachy arrhythmia.

Various methods for treating these arrhythmias are well known in the art. Typical methods for terminating aπ-hythmias include both anti tachy pacemakers which deliver electrical stimulation at a specific site in the heart and ablation therapies. For ablation a radio frequency (RF) probe is placed into direct contact with the tissue site and RF electrical energy is delivered to the site to create a lesion. These lesions are typically electrically inactive and serve to interrupt the re-entrant circuit. Implantable pharmacological defibrillating devices, which combine electrical stimulation with endocardial drug delivery, are also known in the art. For example, see Cammilli et al..

U.S. Pat. No. 5,220,917, issued June 22, 1993.

Catheters used for temperature ablation of endocardial tissue are known in the art. For example, see Milder et al.. U.S. Pat. No.'s 5.281.213: 5,281,215, and 5,423,807, which teach catheters with cooling systems and cryogenic mapping techniques. Nardella. U.S. Pat. No. 5,334,193 teaches fluid-cooled ablation catheters with temperature monitoring capability for treatment of cardiac arrhythmia. Also, Had. U.S. Pat. No. 5,139,496, teaches ultrasonic freeze ablation catheters for treatment of arrhythmia. Typically, the tip ofthe catheter is cooled below the freezing point to ablate the tissue. However, these devices cause permanent tissue damage as a method for treatment.

SUMMARY OF THE INVENTION It is an object ofthe invention to provide an implantable device for treating cardiac arrhythmias, in particular atrial fibrillation, by temporally altering the cardiac tissue temperature at a specific set of locations. Since this effect is temporary, permanent damage of cardiac tissue is no longer required to interrupt the arrhythmia.

In particular, the device includes a thermal catheter for insertion into a chamber ofthe heart. Both atrial and ventricular locations are contemplated within the scope of the invention. The catheter contains both a sensor electrode for detecting arrhythmic activity and a Peltier device or the like for altering the temperature of heart tissue. The catheter may raise or lower the temperature from the ambient state. And heart tissue may be either heated or cooled depending on the desired therapeutic strategy.

In one embodiment, the catheter also contains a lumen structures for infusing a drug directly into the circulatory system from a reservoir contained in the device. In use the device provides a method for temporary, non-ablative and non-damaging temperature manipulation ofthe endocardial environment, resulting in inhibition of cardiac arrhythmias. Further, when drug infusion is used in conjunction with temperature alteration, dosage requirements of pharmaceutical agents may also be altered and perhaps reduced. The combined temperature and drug therapy may serve to quickly terminate and then prevent further arrhythmia. The invention may be used in conjunction with other heart rhythm management technologies, such as conventional pacemaker rhythm management protocols.

BRIEF DESCRIPTION OF THE DRAWINGS Throughout the figures, like reference numerals refer to identical or equivalent structures; wherein:

FIG. 1 is a schematic view ofthe overall system using the device. FIG. 2 is a schematic view of a thermal catheter. FIG. 3 is a schematic view of an alternate thermal catheter.

DETAILED DESCRIPTION OF THE INVENTION As used herein, the term "arrhythmia" is used to include a variety cardiac rhythm disturbances, including atrial tachycardia and atrial fibrillation. The term "non-ablative" as used herein is used to describe the absence of prolonged or permanent tissue damage which results from temperature change.

FIG.l shows a therapy generator 7 coupled to a thermal catheter 2. The thermal catheter 2 is depicted located within the atria of a heart 1, and the distal tip 4 ofthe thermal catheter is in contact with the wall ofthe atrium at the target tissue site. As can be seen in the figure, the thermal catheter 2 is formed into a "J-shape", and the catheter body 3 may have multiple thermal treatment sites to contact a large portion ofthe heart wall. Other lead configurations may be used in the ventricular chamber ofthe heart, and both chambers may be treated as well.

The thermal catheter 2 is coupled to the therapy generator 7. In general, the therapy generator 7 will have a can 8, which is coupled to a connector block 16. The thermal treatment catheter 2 will connect to the connector block 16, and suitable electrical and hydraulic connections will be made with the circuit module 12 and reservoir 9 and pump 17 located within the can 8. A suitable battery 10 is provided to power the circuit module 12 and to power the thermal catheter 2 system and the drug infusion system. The circuit module 12 may be made using conventional pacemaker technologies and may include a sense amplifier 13 coupled to the sensing electrode 5 or sensing electrode 6. Computer logic 11 is supplied to interpret the signal generated by the sense amplifier 13. In general, the computer logic 11 will activate either the thermal treatment generator 15 or the reservoir pump 17 or both in response to the detection of an arrhythmia.

Any of a number of suitable algorithms may be used to detect and declare the presence of arrhythmia. For example, atrial or ventricular rate may be used as a threshold parameter, as well as rate acceleration. If both atrial and ventricular catheters are used, then dissociation between the electrical activity between chambers may be used to indicate a treatable arrhythmia.

Once the computer logic 11 has declared abnormal arrhythmic activity, treatment is invoked. A suitable control signal is issued through connection 14 to the thermal generator 15. The thermal generator in turn couples power through a suitable connection 20 to the thermal catheter 2. It is preferable to use Peltier devices which are semiconductor devices which can either cool or heat depending on applied polarity.

Although such devices are well known in the present application polarity may be reversed and the tissue may be heated or cooled or both heating and cooling may be applied sequentially under the control ofthe thermal treatment controller 15. The therapy generator monitors the rhythm ofthe heart and alters the temperature of target site tissues so that the conduction velocity of electrical impulses in that target tissue interrupts the arrhythmia in that tissue. The thermal catheter can deliver either "hot" or "cold" therapy. Either approach affects conduction velocities of cardiac cells. Reducing or increasing temperature will depend upon the desired therapeutic strategy. Tissue conduction is generally known to be caused by the transmission of ions either through cellular membranes and along fibers in cardiac tissue. Changes in temperature are generally known in the pharmaceutical field as having profound effects on chemical reaction rates. In first order reactions, a 10° C drop in temperature can effect a rate decrease of 50 percent. While such linear relationships are not expected in the use of this invention, it is expected that lowering the temperature ofthe tissue results in slowed transmission of ionic currents which will become too slow to allow propagation in the re-entrant circuits. In the case of increasing temperature, the increase should cause a depletion of ions in a localized area so that currents are again lowered. The temperature is modified to a point sufficient to terminate arrhythmia, as in the case of cooling, or sufficient to terminate arrhythmia or effectuate therapeutic rates, as in the case of heating. The temperature may be increased above or decreased below ambient temperature according to need, provided no tissue damage occurs as a result. In the case of cooling, the phrase "sufficient to terminate arrhythmic activity" means that the temperature is reduced to between about 10° C to 35° C, preferably in the range of about 25° C to 35° C, more preferably to about 30° C. While it is recognized that temperatures between about 10° to 30° C are possible, such temperatures are not necessary in order to be effective for the purposes ofthe invention. For heating, the phrase "sufficient to terminate arrhythmic activity" means that the temperature is increased up to no greater than approximately 50° C, preferably up to about 45° C.

Either temperature modification may last up to approximately 1 minute, although it is preferred that the duration be for about 5 to 10 seconds. Both the "cold" and "hot" therapy are accomplished by the "chilling" and "warming", respectively, ofthe blood immediately surrounding the thermal catheter and the target tissue site itself. The thermal treatment may be used alone or in conjunction with drug infusion or other therapy. When drug infusion is used in conjunction with heat treatment, the phrase "sufficient to increase the reaction rate of a drug" indicates the temperature parameter as used to describe heat treatment alone, provided the temperature used does not significantly alter the therapeutic properties ofthe infused drug. When drug delivery is indicated, the logic 11 issues a signal through connection 19 to the pump 17, which pumps the contents from the reservoir 9 into the lumen 27 ofthe thermal catheter through a suitable connection 18.

The infusion system for drug delivery can be that of any mechanical and/or electrical system capable of delivering a dosage ofthe drug into the heart. Such system can consist of a rotary electric pump, a linear electromagnetic pump, an elastic mechanical system, or hydropneumatic system.

Various drugs which are capable of modifying the electrical activity of cardiac tissue are known in the art. Classes of anti aιτhythmic drugs which may be used in accordance with the invention include sodium channel blockers, beta blockers, calcium channel blockers. Examples of sodium channel blockers include quinidine, procainamide, disopyramide, lidocaine, tocainide, mexiletine, phenytoin, flecainide, and moricizine. Examples of beta blockers include propranolol, acebutolol, esmolol, sotalol, amiodarone, bretylium. Examples of calcium channel blockers include verapamil. Selection of drug to be used will depend upon the desired treatment strategy and that other anti arrhythmic drugs not specifically mentioned are also suitable for practicing the invention. Increasing temperature of localized tissue will improve the effectiveness of many such pharmaceutical agents. Accordingly, lower concentrations and more systematically tolerable dosages ofthe selected drug can be used.

In order to cause the cessation of re-entrant circuits, it may be necessary to alter the temperature at several tissue sites. Accordingly, a multiple site thermal catheter as depicted in the figures may be used. The multiple site thermal catheter has several Peltier devices or thermal conductors exhibiting the ability to come into contact with several areas of tissue at once, thus expanding the area of treated tissue. FIG.2 shows a schematic view of an illustrative cooling version ofthe thermal catheter 2 designed for ventricular or atrial use. The catheter body 3 may be made of silicone rubber or another biocompatible material. The distal tip 4 includes an active fixation screw 21 which is thermally connected to the cooling/heating device 22. The cooling device may be a Peltier device or other electrically powered device. It is contemplated that phase change cooling may be used as well, although electrical cooling is illustrated for simplicity of implementation. In the figure, the Peltier device is in thermal contact with the active fixation tip. However, in another embodiment, a J- shaped configuration is shown where the cross-section ofthe body ofthe catheter may be asymmetrical or oval-shaped to cause the body 3 to conform to the wall ofthe heart. In this instance, it is desirable to locate the Peltier device off-center within the body so that they lie in close proximity to the cardiac wall.

A ring electrode 5 may be positioned near the distal tip electrode 4 to monitor heart rhythm. A separate lumen 23 terminating in a port 24 may be provided as well so as to deliver drugs from the reservoir 9 to the circulatory system.

FIG.3 is a schematic view of an illustrative cooling/heating version ofthe thermal catheter 2 for ventricular use. In this example, multiple Peltier elements depicted as cooling/heating element 25, cooling/heating element 26, and cooling/heating element 27, are located along the length of catheter body 3. A distal section of tines 28 may be used to trap the catheter in the trabaculae ofthe ventricle ofthe heart. The catheter body may also have a drug delivery lumen 23 and a drug delivery port 24 along the body 3 proximal ofthe distal tip electrode. The distal tip electrode 6 is shown coupled to a conductor 29 to monitor cardiac rhythm.

Since the catheter is located within a beating heart, the general construction must be flexible and mechanically robust. It is to be expected that conventional pacemaker lead technologies and construction techniques may be used to create a suitable thermal treatment catheter 2.

The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that reasonable variations and modifications are possible from the foregoing disclosure without departing from either the spirit or scope ofthe present invention as defined by the claims.

Claims

What is claimed is:

1. An implantable device for the treatment of cardiac arrhythmias in a patient comprising: a therapy generator having a can; a battery located within said can; sense amplifier and logic circuitry located within said can coupled to said battery; a thermal catheter coupled to said therapy generator, at least one electrode located on said thermal catheter; at least one Peltier device located on said thermal catheter; whereby said catheter positions said electrode and said Peltier device in contact with cardiac tissue; said sense amplifier and logic circuitry coupled to said electrode for detecting cardiac arrhythmia and for generating a arrhythmia detection signal; said Peltier device coupled to said logic circuitry for altering said cardiac tissue temperature in response to said arrhythmia detection signal.

2. The device of claim 1 further comprising: a reservoir and pump located in said can means for infusing the contents of said reservoir in to the patient in response to said arrhythmia detect signal.

3. The device of claim 1 or claim 2 wherein: said Peltier device is operated to heat cardiac tissue above ambient temperature.

4. The device of claim 1 or claim 2 wherein: said Peltier device is operated to cool cardiac tissue below ambient temperature.

5. The device of claim 2 further comprising : a lumen located in said thermal catheter coupled to said reservoir for dispensing the contents ofthe reservoir into a heart chamber.

6. A method of treating endocardial tissues of a patient for interrupting cardiac arrhythmias comprising: sensing an arrhythmia and generating a detection signal; altering the temperature of endocardial tissue to a temperature sufficient to terminate arrhythmic activity in response to the occurrence of said detection signal.

7. The method of claim 6 further comprising : infusing a drug into the patient in response to said detection signal.

8. A method of endocardial treatment of cardiac arrhythmias comprising: sensing an arrhythmia and generating a detection signal; increasing the temperature of endocardial tissue to a temperature sufficient to terminate arrhythmic activity in response to the occurrence of said detection signal by increasing the temperature of blood in proximity to said tissue in a temporary, non-ablative manner.

9. The method of claim 8 wherein the cardiac arrhythmia treated is atrial fibrillation.