WO2000018308A1

WO2000018308A1 - Device for producing reversible damage to heart tissue

Info

Publication number: WO2000018308A1
Application number: PCT/US1999/022694
Authority: WO
Inventors: Michael D. Laufer; Bruce D. Stambaugh; Hien V. Nguyen
Original assignee: Hearten Medical
Priority date: 1998-09-30
Filing date: 1999-09-29
Publication date: 2000-04-06
Also published as: WO2000018308A9; WO2000018308A8; AU6503799A

Abstract

A medical or surgical device (10) creates holes in heart tissue utilizing a needle (20) connected to an energy source (34), such as a radio frequency generator, a resistive heating source, or a microwave energy source. The needle (20) is inserted into heart tissue and activated to heat the surrounding tissue in order to produce reversible tissue damage. The device consists of any energy source (34), and regulator (48), a handle (18), and a needle (20) at the distal end of the handle. A temperature sensor (46) may be positioned on the needle. Preferably, a regulator (48) is connected to the energy source (34), and to the temperature sensor for controlling the temperature of the heart tissue in which the needle has been inserted.

Description

DEVICE FOR PRODUCING REVERSIBLE DAMAGE TO HEART TISSUE

BACKGROUND OF THE INVENTION Field of the Invention The invention relates to a medical/surgical device and method for treating the heart, and more particularly, the invention relates to a device and method for creating holes in heart tissue.

Brief Description of the Related Art

Currently there are a number of companies using lasers to create holes in heart tissue, for example, Cardiogenesis Corporation of Sunnyvale, CA; PLC Systems, Inc. of Franklin, MA; and Eclipse Surgical Technologies, Inc. of Palo Alto, CA. Each of these companies are utilizing lasers as an energy source to vaporize heart tissue to create a plurality of holes in the heart for treating angina and heart ischemia. Angina is sever cardiac pain most often due to ischemia of the myocardium. Ischemia is localized tissue anemia due to a partial or temporary obstruction of inflow of arterial blood. Ischemic tissue in the heart is usually found in the left ventricle due to obstruction or constriction of the coronary arteries. The procedure of forming holes in the myocardial tissue of the heart is referred to as transmyocardial revascularization ("TMR"). The purpose of TMR is to improve blood flow to under perfused myocardium. The laser created TMR holes are generally formed in the left ventricle. The holes are typically 1 mm in diameter and are placed on a 1 cm by 1 cm grid. Depending on the extent of the angina and ischemia, the laser is used to make somewhere between 10 and 50 holes. Once the holes are created, the holes are sealed off at an exterior of the heart using pressure on the epicardial surface to prevent bleeding into the pericardium.

Studies of TMR procedures on humans have had encouraging results. For example, studies have found a two class reduction in angina in some patients following TMR surgery. This two class reduction of angina greatly increases the quality of life for patients suffering from classes III and IV angina. Patients having classes III and IV angina may not be able to carry on daily activities such as walking without sever pain and may be frequently hospitalized due to heart pain. Following TMR surgery some class III and IV angina patients experience mixiimal or no angina for up to two years following surgery. Although these studies show that the TMR procedure improved the patients condition and quality of life, it is not yet clear how the formation of holes in the myocardium provides this marked improvement in patient condition. Three hypophysis for the improvement which has been observed are that 1) blood flow through the TMR channels directly perfuses the myocardium, 2) damage to heart tissue from ablation and heat of the laser causes release of growth factors that result in angiogenesis, and 3) destruction of nerve pathways mask angina and prevents pain. Because the positive results of TMR surgery last up to two years, and the channels have closed by this time, it is believed that direct tissue perfusion is not the sole reason for the observed improvement. Currently TMR is being performed utilizing a laser source of energy which forms a hole all the way through the heart tissue. Once the holes are formed by the laser, the surgeon, must cover the hole by placing a finger on the epicardial surface until the hole clots shut or the surgeon may use a suture to close the hole. Another disadvantage of the use of a laser is the cost. The laser energy source for use in this procedure costs between about $200,000 to $700,000. This creates a high cost of performing the TMR procedure. Additionally, the laser TMR procedure vaporizes viable heart tissue.

Accordingly, it would be desirable to provide a cost effective supply of energy to create holes in heart tissue. It is also preferable that the energy delivery system does not vaporize viable heart tissue, and does not form holes all the way through the heart tissue.

SUMMARY OF THE INVENTION

The present invention relates to a device that creates holes in heart tissue utilizing radio frequency ("RF") energy, resistive heating, microwave energy, or the like. The device consists of an energy source and regulator, electric contacts (cable) to the energy source, a handle, and a needle at the distal end of the handle for delivering energy to the heart tissue. The RF energy source, resistive heating source, or microwave source is significantly less expensive than the laser energy supply. In addition, the needle on the device does not vaporize heart tissue but instead creates a zone of reversible tissue damage caused by the heating of the tissue. Thus, the present invention provides a significant advance over the current laser TMR therapy.

In accordance with one aspect of the present invention, a medical device for treating ischemia and angina includes a needle, a device handle for supporting the needle and delivering energy to the needle, and a temperature sensor positioned on the needle for sensing a temperature of heart tissue in which the needle has been inserted. An energy source is connected to the needle, and a regulator is connected to the energy source and the temperature sensor for controlling the temperature of the heart tissue in which the needle has been inserted to about 40 °C to about 60 °C as sensed by the temperature sensor.

In accordance with an additional aspect of the present invention, a method of treating ischemia and angina by causing reversible damage to myocardial tissue includes the steps of inserting a needle into the myocardial tissue, and heating the myocardial tissue to between about 40°C and about 60°C with the needle to create a zone of reversible tissue damage around the needle.

In accordance with a further aspect of the invention, a resistance heating device for treating ischemia and angina includes a needle having a coiled resistance element, a source of electric power, a device handle for supporting the needle and transmitting electric power from the source of electric power to the needle, and a thermocouple positioned on the needle for sensing a temperature of heart tissue into which the needle has been inserted. A regulator is connected to the source of electric power and the thermocouple for controlling the supply of electric power to achieve temperatures of between about 40 °C and about 60 °C as sensed by the thermocouple.

The present invention provides advantages of a TMR device which does not vaporize viable heart tissue or create holes al the way through the heart tissue. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference to the preferred embodiments illustrated in the accompanying drawings, in which like elements bear like reference numerals, and wherein: FIG. 1 is a cross sectional view of a left ventricle of a heart with a device for creating holes in the heart tissue;

FIG. 2 is a cross sectional view of a left ventricle of a heart with an alternative embodiment of a device for creating holes in the heart tissue;

FIG. 3 is a side view of a device for creating holes in heart tissue; FIG. 4 is a top view of the device of FIG. 3;

FIG. 5 is a side view of a resistive heating device for creating holes in heart tissue;

FIG. 6 is a partial cross sectional view of a needle assembly for the resistive heating device of FIG. 5; and FIG. 7 is a partial cross sectional view of a battery powered resistive heating device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a device and method for transmyocardial revascularization ("TMR") utilizing a needle connected to an energy source for heating heart tissue. FIG. 1 is a schematic illustration of the device 10 according to the present invention with a needle 20 inserted into left ventricular tissue of the heart. The left ventricle is illustrated in cross-section with the mitral valve (the valve controlling blood flow from the left atrium to the left ventricle) not illustrated. The left ventricle wall 12 is primarily composed of heart muscle tissue. When the muscle tissue contracts, blood is expelled from the ventricle through the aortic valve 14, and into the aorta 16 for delivery blood to the body. When the myocardium or muscle tissue is under perfused, it cannot successfully achieve the function of delivering blood to the body. The surgical device 10 for creating holes includes a handle 18 with a needle

20 attached at the distal end of the handle. The needle 20 is introduced into the tissue of the left ventricle starting on the epicardial surface 22 and penetrating the myocardial tissue 24. The needle 20 preferably does not penetrate the endocardial surface 26. After inserting the needle 20, the tissue 24 is heated by application of energy to the needle. As will be discussed in further detail below, the energy applied to the needle may be radio frequency ("RF") energy, inductive heating, or microwaves.

The heating of the myocardial tissue 24 by application of energy creates a zone of reversible tissue damage surrounding the needle 20. In accordance with the present invention, the size of the zone of reversible tissue damage is preferably maximized while the area of permanent tissue damage is minimized. This is achieved by heating the heart tissue to about 40 °C to about 60 °C, preferably about 44°C to about 50°C for a time of between about 5 and 120 seconds. The reversible tissue damage area acts like a bruise and causes angiogenesis (creation of capillaries and arteries) and arteriogenesis (creation of small arteries). The newly created blood vessels resulting from the treatment improve tissue perfusion and relieve chronic ischemia and angina.

As illustrated in FIG. 1, preferably the needle 20 is inserted into the heart tissue 24 so that it does not puncture the endocardial surface 26. When energy is applied to the needle 20, the zone of reversible tissue damage created around the needle extends radially from the needle and axially from the tip of the needle. Accordingly, the zone of reversible tissue damage will preferably extend all the way through to the endocardial surface. Although FIG. 1 illustrates visible holes 36 formed though the myocardial tissue, in fact once the needle 20 has been withdrawn the holes 36 formed by the needle 20 will be very small or even imperceptible.

FIG. 2 illustrates an alternative embodiment of the device 10 in which a proximal end of the needle 20 adjacent the handle 18 is insulated with an insulating sleeve 32 to prevent or minimize heating of the epicardial tissue 22. The insulating sleeve 32 may be made out of a non-RF conducting material such as polyimide to prevent RF energy from heating the epicardial surface of the heart. Alternatively, the insulating sleeve 32 may be formed of a heat insulating material in the inductive heating embodiment or of a microwave insulating material in the microwave embodiment. In the embodiment of FIG. 2, the needle 20 can be inserted all the way through the endocardial surface 26. Energy is applied to the needle 20 from an energy source 34 to heat the heart tissue adjacent the needle. Once sufficient heat has been generated for a sufficient time, a zone of reversible tissue damage is created around the needle 20 where the needle was not insulated. The epicardial surface 22 was spared heating due to the insulating sleeve 32 and thus the heart tissue itself seals the needle hole 36 to prevent blood loss through the hole. This self sealing provides a distinct advantage over prior art methods which require external pressure or sutures to seal the laser holes.

The insulating sleeve 32 is provided to cover the proximal portion of the needle. The length of the insulating sleeve 32 can vary from about 1 mm to 6 mm with a length of 2 mm, 3 mm, 4 mm, and 5 mm being preferred. The diameter of the insulating sleeve 32 is just larger than the diameter of the needle 20. The insulation material could be applied directly to the needle 20 instead of being a sleeve, for example a polyurethane coating could be directly applied to the proximal few millimeters of the needle.

The needle 20 according to the RF or microwave heating embodiment may be made out of a rigid electrically conducting material such as stainless steel. If the needle is to be used for bipolar RF energy delivery, the needle is constructed out of at least two electrically conducting members which are electrically insulated from each other, i.e. two longitudinal strips of stainless steel embedded in a plastic material or a proximal stainless steel tip separated from a distal stainless steel base with plastic in between. The diameter of the needle 20 can vary, however the preferred diameters range from about 0.1 mm to about 3 mm with 0.5 mm, 1.1 mm, 1.4 and 1.7 being presently preferred. The length of the needle can also vary to match the left ventricular wall thickness. For the non-puncturing embodiment of FIG. 1, the needle length is preferably slightly less than a thickness of the heart tissue. Preferably, the needle 20 in the non-puncturing embodiment extends about 80 - 90% of the way through the heart tissue. For example, for tissue about 20 mm thick, a 16 - 18 mm needle, and preferably a 17 mm needle will be used. The needle length for the embodiment of FIG. 2 in which the needle punctures the endocardial surface 26 may be 5 mm to 35 mm, with 20 to 30 mm being presently preferred.

The very distal end of the needle 20 is beveled to provide a sharp point for penetrating the heart tissue. The bevel, however in the RF and microwave embodiments, creates a sharp RF or microwave energy concentration that can disproportionately deliver too much energy from the needle tip. Thus, in a preferred embodiment the beveled tip is coated with a thin layer of an RF or microwave insulating material such as polyurethane. The needle 20 can be directly attached to the distal end of the handle 18, or can be deploy ably retained within the handle and a deploying means may be provided on the handle to deploy the needle.

The handle 18 is constructed out of an RF, microwave, or electric insulating material, preferably a hard plastic material such as acrylonitrile- butadine-styrene ("ABS"), polycarbonate, and the like. The handle 18 can be as simple as a cylinder or a catheter that can be manipulated by a health care practitioner or can be a more complex molded piece which conforms to the hand of the operator. The handle will have at least one lead wire 38 in it to connect the needle 20 to the energy source 34. The embodiment of FIG. 2 has a handle 18 with two finger holes 40. The handle 18 is hollow with a deployable needle 20 located inside the handle. At the distal end of the handle 18 is the insulating sheath 32 that is connected to the handle. The bevel of the needle 20, when at rest, just barely protrudes distally past the insulating sheath 30. The needle 20 is slidably retained within the handle 18 and deployed using a thumb plunger 42 located at the proximal end of the handle. A spring 44 is provided between the thumb plunger 42 and the finger holes 40 to give the plunger resistance and to keep the needle 20 in a relatively retracted at rest position. Translating the plunger 42 distally will translate and deploy the needle 20 distally through the heart tissue. Optionally, a locking mechanism can be provided to keep the needle 20 in a translated position.

The needle 20 is preferably provided with a standard thermocouple 46 welded within the lumen of the needle or on an exterior of the needle. The thermocouple 46 is preferably located about 5 mm from the distal tip of the needle 20. The thermocouple 46 is used to give the operator of the device an indication of the temperature of the needle and thus, the temperature being delivered to the adjacent heart tissue. Alternatively, the energy source may be provided with a regulator 48 for controlling the temperature of the heart tissue in which the needle 20 has been inserted. The regulator 48 is connected to the energy source 34 and to the temperature sensor thermocouple 46 to control the energy supplied to the needle 20 from the energy source and thus control the temperature to which the heart tissue is heated.

In the RF energy embodiment, the RF energy typically ranges from about 100 kHz to about 1,000 kHz, preferably about 400 kHz to about 500 kHz, and more preferably about 460 kHz. The watts of power can vary from about 0.1 watt to about 100 watts, preferably about 3 watts to 25 watts. According to one variation of the RF heating embodiment, the maximum power of the energy source 34 is set to 80 watts initially and the power is then controlled by the regulator 48 to achieve the desired temperature. Many different RF generators can be used to supply the RF energy. Presently, and RF generator manufactured by Stellartech Research Corporation of Mountain View, CA is preferred. The RF generator can deliver a maximum wattage of RF energy, with that maximum wattage chosen by the user of the generator. The RF generator can measure the temperature at a thermocouple inside or outside the needle to regulate the wattage to maintain a set temperature. Presently, a temperature ranging from about 40 °C to about 60 °C is used with a temperature of 44° C to 50° C being presently preferred. The RF energy can be delivered for a set time ranging from 1 second to 500 seconds, with 30 seconds being presently preferred.

An alternative embodiment of the device for producing reversible damage to heart tissue is illustrated in FIGS. 3 and 4. The device 10 of FIG. 3 includes a retractable needle 20 movable within a handle 18. A proximal end of the handle 18 is provided with a lure fitting 50 for connecting the lumen of the needle 20 to a fluid supply. The needle 20 is electrically connected to a cable 52 for delivery of energy from the energy source 34 to the distal end of the needle 20. The device 10 is also provided with a knob 54 for moving the needle 20 between an extended and a retracted position. The knob 54 is secured to the needle by a sleeve 56 and a shaft 58 of the knob 54 travels along a first slot 60 in the handle 18. The first slot 60 is shown most clearly in FIG. 4. A second slot 62 at a proximal end of the handle 18 allows the cable 52 which is connected to the needle 20 to travel longitudinally within the handle as the needle is extended and retracted.

According to one embodiment of the present invention, the lumen of the needle 20 can be used to deliver beneficial agents to the heart tissue during or after the TMR procedure. For example, a syringe may be attached to the lure fitting 50 for delivery growth factors into the hole formed by the needle. Examples of growth factors include vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), monocyte attracting protein (MAP), and the like.

FIGS. 5 and 6 illustrate a resistive heating embodiment of a device for producing reversible damage to heart tissue. The resistive heating device 70 as illustrated in FIG. 5 includes a needle 72 extending from a handle 74. The handle 74 is connected by a cable 76 to the energy source 34 (not shown) which in this embodiment is an electric power supply. At a distal end of the handle 74 is a soft disk shape stop member 78. The stop member 78 functions to limit the penetration of the needle 72 into the heart tissue. The stop member 78 is preferably formed of a soft flexible material such as rubber which will assist the surgeon in holding the needle 72 in place in the heart tissue at the desired depth particularly during beating heart surgery. The stop member 78 may be secured to the needle 72 or to the handle 74 such as by epoxy. Alternatively, the stop member 78 may be held in place by a friction fit. FIG. 6 illustrates a needle assembly 80 for use in the resistive heating device 70 of FIG. 5. The needle assembly 80 includes a central core or wire 82 formed of a conductive material such as a 0.011 inch stainless steel wire. An insulating jacket 84 surrounds the wire 82 and provides insulation between an inner core and an outer core of the needle 72. The insulating jacket 84 may be any form of insulating tubing or coating such as polyimide tubing. Surrounding the insulating jacket 84 is a coiled resistance wire 86 which is preferably an alumel wire which provides the resistive heating of the device. The resistance wire 86 is connected to the inner core or wire 82 by a solder joint 88 at the distal tip of the needle. A proximal end of the coiled resistance wire 86 is electrically connected to an electrode wire 90 formed of a conductive material. The inner core wire 82 and the electrode wire 90 are connected by the cable 76 to the positive and negative terminals of the electric power source. A heat shrink tubing 92 may be provided over the resistance wire 86 to completely enclose the resistive elements of the needle.

A thermocouple assembly is preferably provided over the heat shrink tubing 92. The provision of the thermocouple assembly at an exterior of the needle 72 allows the thermocouple to be directly in contact with the heated tissue in which the needle has been inserted to accurately sense a temperature of the tissue. The thermocouple assembly may include a thermocouple 96 sandwiched between two insulating jackets. The thermocouple 96 may be any known thermocouple, such as a thermocouple formed of a chrome alumel and constantan wire. Lead wires are provided to connect the thermocouple 96 to the regulator for control of heating of the tissue. The resistive heating device 70 according to FIGS. 5 and 6 may be connected to either an AC or DC power supply. According to one preferred embodiment of the invention, the resistive heating device is a disposable battery powered device 100 including a battery 102 contained within a compartment 104 within the handle 106 as shown in FIG. 7. Also enclosed within the compartment 104 is a printed circuit board/microprocessor 108 to control the temperature of the needle 110.

In use of the embodiment of FIG. 1, the needle is inserted into the heart tissue by a health care practitioner, preferably a physician, under a procedure that exposes the heart. The needle is placed such that the needle's distal tip does not penetrate the endocardial surface 26 as shown in FIG. 1. A stop 78 as shown in FIG. 5 may be used to limit the depth of the needle. In addition, to ensure that the needle does not puncture the endocardial surface, appropriate feedback mechanisms can be used such as echocardiography, electrograms, theroscopy, and the like. Energy is then applied to the needle from the energy source 34 to heat the tissue surrounding the needle and cause reversible tissue damage. The regulator 48 controls the temperature of the heart tissue to a temperature of about 40°C to about 60°C, and preferably about 44 to about 50°C as sensed by the thermocouple. Heating is continued for between about 5 and 120 seconds, preferably about 30 seconds. The needle is then removed and the procedure is repeated as needed to generate an appropriate number of holes depending on the patients condition. The resulting holes are surrounded by a relatively large area of reversible tissue damage which causes increased angiogenesis and/or arteriogenesis. Over time, the ischemic area of the heart which has been treated becomes better perfused with blood and the patient with angina experiences less pain. According to the alternative embodiment illustrated in FIG. 2, the needle

20 is inserted through the heart tissue by a health care practitioner into the left ventricular cavity and the insulating sheath 32 pierces the epicardial surface 22 as shown in FIG. 2. To ensure that the tip of the needle 20 is in the left ventricle, a feedback mechanism can be used. Some appropriate feedback mechanisms include echocardiography, electrograms taken at the very distal tip of the needle, pressure readings at the tip of the needle, or providing a hollow needle that allows blood to flash back at the proximal end into a flash chamber similar to standard IV catheter kits. Energy is then applied to the needle as in the embodiment of FIG. 1 to heat the tissue surrounding the needle and cause reversible tissue damage. Then the needle is removed and the procedure repeated as needed to generate the appropriate amount of holes. The result is that a channel is created in the heart to allow blood to flow in and out of the channel during the contracting of the heart muscle. Additionally, the reversible tissue damage can be the source of growth factors that initiates angiogenesis and/or arteriogenesis.

The method and apparatus according to the present invention provide several advantages over the prior art TMR methods employing lasers. In particular, the known laser procedure punctures the heart tissue all the way through allowing bleeding into the pericardium and requiring the additional step of application of pressure to cause clotting or stitching the holes close. The present invention achieves the benefits of laser TMR without puncturing all the way through the heart tissue. In addition, the present invention causes less permanent damage to the heart tissue because it does not remove or vaporize tissue. Because tissue is not removed, possible overlapping of holes does not create the same problems in the present invention as in laser TMR procedures. Finally, the TMR procedure according to the present invention employing radio frequency energy, resistive heating, or microwave energy are much less expensive energy sources than the lasers required for laser TMR. While the invention has been described in detail with reference to the preferred embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made and equivalents employed, without departing from the present invention.

Claims

WHAT IS CLAIMED IS:

1. A medical device for treating ischemia and angina, the device comprising: a needle; a device handle for supporting the needle and delivering energy to the needle; a temperature sensor positioned on the needle for sensing a temperature of heart tissue in which the needle has been inserted; an energy source connected to the needle; and a regulator connected to the energy source and the temperature sensor, for controlling the temperature of the heart tissue in which the needle has been inserted to about 40 °C to about 60 °C as sensed by the temperature sensor.

2. The medical device of Claim 1, wherein the needle has a diameter of 2 mm or less.

3. The medical device of Claim 1, wherein the energy source is a radio frequency generator.

4. The medical device of Claim 3, wherein the radio frequency generator delivers RF energy at about 400 kHz to about 500 kHz.

5. The medical device of Claim 1, wherein the energy source is an electric power source and the needle includes a resistive heating element.

6. The medical device of Claim 5, wherein the electric power source is a battery positioned within the device handle and the device is a self-contained disposable handpiece.

7. The medical device of Claim 5, wherein the needle includes a resistive wire coil.

8. The medical device of Claim 1, wherein the energy source is a microwave source.

9. The medical device of Claim 1, further comprising a flexible disk shaped stop member for limiting the penetration of the needle.

10. The medical device of Claim 1, wherein the needle is movable longitudinally within the device handle to vary a penetration depth of the needle.

11. The medical device of Claim 1 , wherein the needle includes an insulating sleeve spaced from a distal end of the needle for preventing heating of the epicardial tissue.

12. A method of treating ischemia and angina by causing reversible damage to myocardial tissue, the method comprising: inserting a needle into the myocardial tissue; and heating the myocardial tissue to between about 40 °C and about 60 °C with the needle to create a zone of reversible tissue damage around the needle.

13. The method of treating ischemia and angina of Claim 12, wherein the tissue is heated for between about 5 seconds and about 120 seconds.

14. The method of treating ischemia and angina of Claim 12, wherein the needle is inserted all the way through a heart wall.

15. The method of treating ischemia and angina of Claim 12, wherein the needle is inserted part way through a heart wall.

16. The method of treating ischemia and angina of Claim 12, wherein the myocardial tissue is heated by applying radio frequency energy to the needle.

17. The method of treating ischemia and angina of Claim 12, wherein the myocardial tissue is heated by resistance heating of the needle.

18. The method of treating ischemia and angina of Claim 12, wherein myocardial tissue is heated by applying microwave energy to the needle.

19. The method of treating ischemia and angina of Claim 12, wherein the myocardial tissue is heated to a temperature of between about 44 °C and about 50°C.

20. The method of treating ischemia and angina of Claim 12, wherein the needle is removed and reinserted to form a plurality of spaced apart zones of reversible tissue damage.

21. A resistance heating device for treating ischemia and angina, the device comprising: a needle including a resistance element; a source of electric power; a device handle for supporting the needle and transmitting electric power from the source of electric power to the needle; a thermocouple positioned on the needle for sensing a temperature of heart tissue into which the needle has been inserted; a regulator connected to the source of electric power and the thermocouple for controlling the supply of electric power to achieve a predetermined temperature as sensed by the thermocouple.

22. The resistance heating device of Claim 21, wherein the predetermined temperature is between about 40 °C and about 60 °C.

23. The resistance heating device of Claim 21, wherein the needle has a length of about 15 mm to about 20 mm.

24. The resistance heating device of Claim 23, wherein the thermocouple is positioned about 3 mm to about 10 mm from a distal tip of the needle.

25. The resistance heating device of Claim 21, wherein the source of electric power is a battery and the handle includes a battery compartment for receiving the battery.

26. The resistance heating device of Claim 21, wherein the needle includes a conductive core surrounded by and insulating sleeve and the resistance element is coiled around the insulating sleeve and electrically connected to the conductive core at a distal tip of the needle.

27. The resistance heating device of Claim 26, wherein distal ends of the conductive core and the coiled resistance element are connected to positive and negative terminals of the source of electric power.