Surgery – Instruments – Cyrogenic application
Reexamination Certificate
2002-07-11
2004-11-02
Gibson, Roy D. (Department: 3739)
Surgery
Instruments
Cyrogenic application
C606S022000, C606S023000
Reexamination Certificate
active
06811550
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to apparatus and methods for inhibiting restenosis in blood vessels following angioplasty or other intravascular procedures for treating atherosclerosis and other diseases of the vasculature. More particularly, the present invention provides improved apparatus and methods for cryogenically treating a lesion within a patient's vasculature to inhibit hyperplasia (which often occurs after 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). PTA 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 and stenting, 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 typically occurs within weeks or months of the primary procedure, and may affect up to 50% of all angioplasty patients to some extent. Restenosis results at least in part from smooth muscle cell proliferation in response to the injury caused by the primary treatment. This cell proliferation is referred to as “hyperplasia.” Blood vessels in which significant restenosis occurs will typically require further treatment.
A number of strategies have been proposed to treat hyperplasia and reduce restenosis. Previously proposed 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 these proposal have enjoyed varying levels of success, no one of these procedures is proven to be entirely successful in avoiding all occurrences of restenosis and hyperplasia.
It has recently been proposed to prevent or slow reclosure of a lesion following angioplasty by remodeling the lesion using a combination of dilation and cryogenic cooling. Co-pending U.S. patent application Ser. No. 09/203,011, filed Dec. 1, 1998, the full disclosure of which is incorporated herein by reference, describes an exemplary structure and method for inhibiting restenosis using a cryogenically cooled balloon. While these proposals appear promising, the described structures and methods for carrying out endovascular cryogenic cooling would benefit from still further improvements. In particular, work in connection with the present invention has shown that the antiproliferative efficacy of endoluminal cryogenic systems can be quite sensitive to the temperature to which the tissues are cooled.
Although cryogenic cooling shows great promise for endovascular use, it can be challenging to safely and reproducibly effect the desired controlled cooling. For example, many potential cryogenic fluids, such as liquid nitrous oxide, exhibit high levels of heat transfer. This is problematic as high cooling temperatures may kill the cooled cells (cell necrosis) rather than provoking the desired antiproliferative effect of endoluminal cryotherapy. Work in connection with present invention suggests that other cryogenic fluids, such as the AZ-50™ fluorocarbons (which may exhibit more ideal temperature characteristics), may raise bio-compatibility and safety concerns. Additionally, improved safety measures to minimize any leakage of even biocompatible cryogenic fluids into the blood stream would be beneficial. Further, cryogenic systems that result in liquid vaporization within the balloon surface can decrease the temperature to which tissues are cooled and thus reduce the efficacy in inhibiting hyperplasia.
For these reasons, it would be desirable to provide improved devices, systems, and methods for treatment of restenosis and hyperplasia in blood vessels. It would be particularly desirable if these improved devices, systems, and methods were capable of delivering treatment in a very controlled and safe manner so as to avoid overcooling and/or injury to adjacent tissue. These devices, systems, and methods should ideally also inhibit hyperplasia and/or neoplasia in the target tissue with minimum side effects. At least some of these objectives will be met by the invention described herein.
2. Description of the Background Art
A cryoplasty device and method are described in PCT Publication No. WO 98/38934. Balloon catheters for intravascular cooling or heating a patient are described in U.S. Pat. No. 5,486,208 and PCT Publication No. 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. A body cooling apparatus is described in U.S. Pat. No. 3,125,096. Rapid exchange catheters are described in U.S. Pat. Nos. 5,383,853 and 5,667,521. A MEINHARD® nebulizer is described at the following website: http://www.meinhard.com/product3.htm. The following U.S. Patents may also be relevant to the present invention: U.S. Pat. Nos. 5,458,612; 5,545,195; and 5,733,280.
The full disclosures of each of the above references are incorporated herein by reference.
SUMMARY OF THE INVENTION
The present invention provides improved devices, systems, and methods for inhibiting hyperplasia in blood vessels. The blood vessels will often be treated for atherosclerotic or other diseases by balloon angioplasty, arthrectomy, rotational arthrectomy, laser angioplasty, stenting, or another primary treatment procedure. Inhibition of excessive cell growth is desirable when such treatments are employed so as to reduce and/or eliminate any associated hyperplasia and to maintain the patency of a body lumen. The present invention allows for cryotherapy treatment of a target portion within the body lumen of a patient in a very controlled and safe manner, particularly when using fluid capable of cooling tissues below a target temperature range.
In a first aspect, the invention provides a cryotherapy catheter comprising a catheter body having a proximal end and a distal end with a cooling fluid supply lumen and an exhaust lumen extending therebetween. A first balloon is disposed near the distal end of the catheter body in fluid communication with the supply and exhaust lumens. A second balloon is disposed over the first balloon with a thermal barrier therebetween.
Treatment according to this first aspect of the present invention can be effected by positioning the first balloon within the blood vessel adjacent a target portion. The “target portion” will often be a length within the blood vessel which is at risk of hyperplasia, typically as a result of balloon angioplasty (or some other treatment). Cryogenic cooling fluid is introduced into the first balloon (in which it often vaporizes) and exhausted. The second balloon expands to radially engage the vessel wall. The target portion is cooled to a temperature which is sufficiently low for a time which is sufficiently long to inhibit excessive cell proliferation. Heat transfer will be inhibited between the first and second balloons by the thermal barrier so as to limit cooling of the target portion. The inhibited cooling
Holland Timothy D.
Joye James
Williams Richard
Williams Ronald
Barrish, Esq. Mark D.
CryoVascular Systems, Inc.
Gibson Roy D.
Townsend & Townsend & Crew LLP
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