Heated perfusion balloon for reduction of restenosis

Details Heated perfusion balloon for reduction of restenosis Heated perfusion balloon for reduction of restenosis

1998-04-20

2001-02-20

Bockelman, Mark (Department: 3763)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S113000, C604S114000, C607S099000, C607S096000

Reexamination Certificate

active

06190355

ABSTRACT:

FIELD OF THE INVENTION
The invention relates generally to a method and apparatus for inhibiting restenosis in coronary arteries after angioplasty. More specifically, the invention includes using a heated perfusion catheter to apply low grade heat to a vessel wall for the purpose of inhibiting restenosis.
BACKGROUND OF THE INVENTION
Coronary arteries provide blood and nutrients to the heart muscle. The arteries are subject to atherosclerosis or hardening of the arteries. Vascular regions have plaques formed within, resulting in stenosed regions having reduced cross-sectional area. The reduced area causes a reduction in transport of blood, oxygen, and nutrients which can result in angina, myocardial infarction and death.
A commonly used method for treating atherosclerosis is Percutaneous Transluminal Coronary Angioplasty (PTCA). PTCA includes insertion of a balloon catheter through an insertion in the femoral artery near the groin, advancement of the balloon over the aortic arch, advancement within the selected coronary artery, continuing until the balloon portion is placed across the stenosed region. The balloon is inflated, widening the narrowed vessel region.
After catheter withdrawal, significant vessel reclosure may develop. The reclosure may occur within hours or days of dilation, an “abrupt reclosure.” When reclosure does occur, it more commonly occurs progressively, within six months of the angioplasty. The gradual reclosure is referred to as “restenosis”, and largely negates the dilatation treatment. More highly stenosed vessel regions have a greater chance of becoming restenosed.
One approach to dealing with restenosis utilizes stents, short tubular sections, placed across the recently dilatated vessel region. Stents can be either self-expanding or balloon-expandable. Stents are normally left in place indefinitely. As the stent is forever pushing radially outward against the vessel wall, the wall can be undesirably irritated over long time periods. Stent ends, which push radially outward, are adjacent to soft tissue which can be irritated by the stent end. Stents commonly have wire mesh or spring structures, with openings in the stent walls. “Intimal hyperplasia”, rapid tissue growth through stent openings has also been reported. While the exact mechanism of restenosis is not understood, it is believed that the vessel narrowing is due more to cellular growth and/or a response to vessel injury than to an elastic rebound mechanism.
Thus, to prevent restenosis, use of a stent, or a stent without additional therapy, may not be a solution for all patients. An alternative to stents or an additional treatment associated with the use of stents may be desirably for some patients.
Once therapy for reducing restenosis which has been suggested is heated balloon angioplasty. Some attempts were directed to making the tissues “flow”, by heating vessel tissue at 60 and 80 degrees C. Other attempts utilized high temperatures for the stated purpose of sealing the splitting of the intimal layers of the blood vessel walls, fusing tissue and coagulating. However, such attempts led to increased rather than decreased restenosis.
What is desirable and has not heretofore been provided is a method for inhibiting restenosis after a stent has been put in place. What would be more desirable is a method for inhibiting restenosis not requiring any stent placement.
SUMMARY OF THE INVENTION
The present invention is directed to a method and apparatus for inhibiting restenosis of blood vessels following angioplasty. In particular, the application of low grade heat to a recently dilatated stenosed vessel wall is believed to confer significant resistance to restenosis.
One method for practicing the invention includes heating a dilatated region vessel wall to a temperature within a 40 to 45 degree C. range for a period greater than 10 seconds. Preferred time periods can be greater than about 30 seconds, including the 30 second to 10 minute and 10 to 60 minute ranges. One preferred temperature range is from about 42 to about 45 degrees C. A preferred method includes heating a vessel wall to a temperature of 43 degrees C. for 3 to 6 minutes.
A preferred source of heat is a balloon catheter having a heating wire formed in a coil, with temperature sensors in the distal portion, electrically connected to a power supply and temperature display unit, respectively. A preferred catheter includes a wire coil which can be heated by the passage of DC, AC, or RF current through the coil. The coil in this embodiment is mounted on the outside wall of a perfusion tube and within a balloon cavity. Inflation fluid within the balloon cavity is in thermal contact with the wire and the balloon envelope is inflated to a low pressure in the range of 1 to 3 atmospheres to effect contact with the inner vessel wall, thereby providing thermal contact with the vessel wall. A heated coil thus provides heat to the vessel wall.
Accurate temperature measurement and control is one aspect of the present invention. Unlike previous heated angioplasty attempts, the purpose is not to fuse tissue but to apply controlled heat to a vessel region. While fusing tissue could be accomplished even without temperature measurement, low grade heat application requires tighter control. Specifically, the temperature should not exceed about 45 degrees C., to prevent cell necrosis. A preferred catheter includes a temperature sensor mounted along the balloon outside wall, for good contact with the vessel wall. A second, reference temperature sensor is optionally provided, measuring bloodstream temperature upstream of the heating device. An optional temperature measurement is a differential measurement of vessel wall temperature over blood temperature.
In another embodiment, radio-frequency (RF) current is supplied by the power supply to electrodes in the catheter head, causing current conduction through the inflation fluid, thereby heating the inflation fluid. In yet another embodiment, the wire in the catheter head is arranged in a configuration suitable for transmitting microwave radiation, including microwave radiation transmitted directly to vessel walls.
The invention provides low grade heat to inhibit restenosis in blood vessels. The variable power supplied, coupled with temperature feedback, provides a system for rapidly converging on proper operating parameters to achieve the desired vessel wall temperature. The perfusion lumen allows perfusing blood flow during the otherwise long treatment period. The invention can be used to treat a vessel region having a stent, to inhibit restenosis which may be caused in part by the stent placement.


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