Surgery – Instruments – Cyrogenic application
Reexamination Certificate
1998-12-01
2002-03-12
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
Cyrogenic application
C606S022000, C606S023000
Reexamination Certificate
active
06355029
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to apparatus and methods for inhibiting restenosis in arteries following angioplasty or other intravascular procedures for treating atherosclerotic disease. More particularly, the present invention relates to apparatus and methods for cryogenically treating the target site within a patient's vasculature to inhibit hyperplasia which can occur after such intravascular procedures.
A number of percutaneous intravascular procedures have been developed for treating atherosclerotic disease in a patient's vasculature. The most successful of these treatments is percutaneous transluminal angioplasty (PTA) which employs a catheter having an expansible distal end, usually in the form of an inflatable balloon, to dilate a stenotic region in the vasculature to restore adequate blood flow beyond the stenosis. Other procedures for opening stenotic regions include directional arthrectomy, rotational arthrectomy, laser angioplasty, stents and the like. While these procedures, particularly PTA, have gained wide acceptance, they continue to suffer from the subsequent occurrence of restenosis.
Restenosis refers to the re-narrowing of an artery within weeks or months following an initially successful angioplasty or other primary treatment. Restenosis afflicts up to 50% of all angioplasty patients and results at least in part from smooth muscle cell proliferation in response to the injury caused by the primary treatment, generally referred to as “hyperplasia.” Blood vessels in which significant restenosis occur will require further treatment.
A number of strategies have been proposed to treat hyperplasia and reduce restenosis. Such strategies include prolonged balloon inflation, treatment of the blood vessel with a heated balloon, treatment of the blood vessel with radiation, the administration of anti-thrombotic drugs following the primary treatment, stenting of the region following the primary treatment, and the like. While enjoying different levels of success, no one of these procedures has proven to be entirely successful in treating all occurrences of restenosis and hyperplasia.
For these reasons, it would be desirable to provide additional apparatus and methods suitable for the treatment of restenosis and hyperplasia in blood vessels. It would be further desirable if the apparatus and methods were suitable for treatment of other conditions related to excessive cell proliferation, including neoplasms resulting from tumor growth, hyperplasia in other body lumens, and the like. The apparatus and method should be suitable for intravascular and intraluminal introduction, preferably via percutaneous access. It would be particularly desirable if the methods and apparatus were able to deliver the treatment in a very focused and specific manner with minimal effect on adjacent tissues. Such apparatus and methods should further be effective in inhibiting hyperplasia and/or neoplasia in the target tissue with minimum side affects. At least some of these objectives will be met by the invention described hereinafter.
2. Description of the Background Art
Balloon catheters for intravascularly cooling or heating a patient are described in U.S. Pat. No. 5,486,208 and WO 91/05528. A cryosurgical probe with an inflatable bladder for performing intrauterine ablation is described in U.S. Pat. No. 5,501,681. Cryosurgical probes relying on Joule-Thomson cooling are described in U.S. Pat. Nos. 5,275,595; 5,190,539; 5,147,355; 5,078,713; and 3,901,241. Catheters with heated balloons for post-angioplasty and other treatments are described in U.S. Pat. Nos. 5,196,024; 5,191,883; 5,151,100; 5,106,360; 5,092,841; 5,041,089; 5,019,075; and 4,754,752. Cryogenic fluid sources are described in U.S. Pat. Nos. 5,644,502; 5,617,739; and 4,336,691.
The full disclosures of each of the above U.S. Patents are incorporated herein by reference.
SUMMARY OF THE INVENTION
The present invention comprises the cryosurgical treatment of a target site within the body lumen of a patient, usually in an artery which has been previously treated for atherosclerotic disease by balloon angioplasty or any of the other primary treatment modalities described above. The present invention, however, is further suitable for treating other hyperplastic and neoplastic conditions in other body lumens, such as the ureter, the biliary duct, respiratory passages, the pancreatic duct, the lymphatic duct, and the like. Neoplastic cell growth will often occur as a result of a tumor surrounding and intruding into a body lumen. Inhibition of such excessive cell growth is necessary to maintain patency of the lumen.
Treatment according to the present invention is effected by cooling target tissue to a temperature which is sufficiently low for a time which is sufficiently long to inhibit excessive cell proliferation. The cooling treatment will be directed against all or a portion of a circumferential surface of the body lumen, and will preferably result in cell growth inhibition, but not necessarily in significant cell necrosis. Particularly in the treatment of arteries following balloon angioplasty, cell necrosis may be undesirable if it increases the hyperplastic response. Thus, the present invention will slow or stop cell proliferation but may leave the cells which line the body lumen viable, thus lessening hyperplasia.
Methods according to the present invention comprise cooling an inner surface of the body lumen to a temperature and for a time sufficient to inhibit subsequent cell growth. Generally, the temperature at the tissue surface will be in a range from about 0° C. to about −80° C., the tissue surface temperature preferably being in a range from about −10° C. to about −40° C. In other embodiments, the temperature at the cell surface can be in the range from −20° C. to −80° C., optionally being from −30° C. to −50° C. The tissue is typically maintained at the described temperature for a time period in the range from about 1 to about 60 seconds, often being from 1 second to 10 seconds, preferably from 2 seconds to 5 seconds. Hyperplasia inhibiting efficacy may be enhanced by repeating cooling in cycles, typically with from about 1 to 5 cycles, with the cycles being repeated at a rate of about one cycle every 60 seconds. In the case of arteries, the cooling treatment will usually be effected very shortly after angioplasty, arthrectomy, rotational arthrectomy, laser angioplasty, stenting, or another primary treatment procedure, preferably within one hour of the primary treatment, more preferably within thirty minutes within the primary treatment, and most preferably immediately following the primary treatment.
The methods of the present invention may be performed with cryosurgical catheters comprising a catheter body having a proximal end, a distal end, and a primary lumen therethrough. The primary lumen terminates in a Joule-Thomson orifice at or near its distal end, and a balloon is disposed over the orifice on the catheter body to contain a cryogenic fluid delivered through the primary lumen. Suitable cryogenic fluids will be non-toxic and include liquid nitrogen, liquid nitrous oxide, liquid carbon dioxide, and the like. By delivering the cryogenic fluid through the catheter body, the balloon can be expanded and cooled in order to effect treatments according to the present invention.
Preferably, the Joule-Thomson orifice will be spaced inwardly from each end of the balloon and the balloon will be sufficiently long so that the cooling of the balloon occurs primarily in the middle. The temperature of the proximal and distal ends of the balloon will thus be much less than that of the middle, and the ends will thus act as “insulating” regions which protect luminal surfaces and other body structures from unintended cooling. Preferably, the balloon has a length of at least 1 cm, more preferably at least 2 cm, and typically in the range from 3 cm to 10 cm. The orifice is usually positioned at least 0.5 cm from each end, pr
Joye James
Williams Ronald
Bains, Esq. Nena
Cryovascular Systems, Inc.
Dvorak Linda C. M.
Kearney R.
Townsend & Townsend & Crew LLP
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