Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
2001-02-22
2003-12-23
Milano, Michael J. (Department: 3731)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
C623S001170, C623S001180
Reexamination Certificate
active
06666882
ABSTRACT:
FIELD OF INVENTION
The present invention is directed to endovascular thin film devices which can be used for treating and preventing stroke, including ischemic stroke caused by a blood clot in a blood vessel in the brain or hemorrhaging stroke caused by aneurysmal subarachnoid hemorrhage.
BACKGROUND OF INVENTION
Cerebrovascular disease is the third leading cause of death in the USA and the leading cause of disability. Strokes affect 500,000 Americans every year. This results in 150,000 stroke-related fatalities per annum, and over 3,000,000 stroke survivors (Wieber et al,
Stroke
23:10, 1992). The cost to the community, including health care expenses and lost productivity, has been estimated at over $30 billion per annum. Neurovascular disorders resulting in thrombo-embolic occlusion of intracranial arteries, resulting in ischemic stroke, and rupture of intracranial aneurysms, resulting in hemorrhagic stroke, are major contributors to stroke-related morbidity and mortality world wide. In contrast to cardiovascular disorders, endovascular treatment strategies for neurovascular disorders have been historically limited by issues of safe access to the cerebral vasculature. Over the past decade advances in digital subtraction angiographic techniques and improvements in microcatheter and microguidewire technology have significantly broadened the scope of minimally invasive neuroendovascular therapy. Today, there is an urgent need for developing medical devices specially designed for deployment via catheter-based techniques for percutaneous endovascular treatment of various devastating neurovascular disorders.
Recent clinical data suggest that patients with acute occlusion of intracranial arteries benefit from rapid removal of the intra-arterial clot and experience an improved outcome. Until now, intracranial clot removal has been primarily accomplished by anticoagulation and thrombolysis. There are several disadvantages to this method of clot removal. First, the clot composition in many patients makes it not feasible to use urokinase or TPA for thrombolysis. Second, if clot lysis is successful, the problem of reperfusion hemorrhage within the distal vascular bed is dramatically magnified due to the patient's anticoagulated condition at the time of reperfusion due to prior administration of thrombolytics and heparin. Third, removal of clot by lysis is much more likely to result in distal embolization of small blood clots in a vascular territory that is at the end arteriorlar level and is beyond the help of collateral circulation from adjacent vessels. Due to these shortcomings, an ideal clot removal system would involve mechanical removal of the blood clot from the intracranial vessel without disruption of the patient's coagulation cascade.
In managing peripheral and coronary atherosclerotic vascular diseases, percutaneous transluminal angioplasty (PTA), usually in combination with percutaneous stent placement, is an alternative to surgical revascularization (Mayberg et al,
JAMA
, 266:3289-3294, 1991; Moiore et al,
Stroke
26:188-201, 1995). There is a growing body of experience with these techniques in the carotid and vertebrobasilar arteries (O'Keefe et al,
JACC
16:1097-1102, 1990; Becker et al,
Radiology
170:921-940, 1989). Various investigators have stented over 100 arteries with technical success in 95 to 99% of vessels. In addition, the morbidity and mortality rates are comparable to those of CEA (stroke rates of 0-8%, incidence of death 0-0.9%, and restenosis rates of 1-8%). Similar efficacy and safety is observed in angioplasty and stenting of other supra-aortic vessels. Together these data suggest that carotid angioplasty and stenting (CAS) is safe, feasible, and a viable alternative to CEA in the treatment of patients with carotid atherosclerotic disease.
There are two major potential limitations of PTA in managing arterial stenosis: restenosis and distal embolism. Although there is limited long-term follow-up after supra-aortic PTAs, several studies suggest that the restenosis rate is less than 10 at 12 months. This is similar to the results of angioplasty in other vessels where the restenosis rate is related to the size of the vessel and type of lesion. Large vessels such as the iliac and proximal femoral arteries have restenosis rates of 20-25% at three years, while smaller vessels (popliteal and coronary arteries) have restenosis rates of 35-45% (Kachel et al,
Neuroradiology
33:191-194, 1991; Criado et al,
American Journal of Surgery
174:111-114, 1997). Following CEA restenosis may occur in up to 36% of vessels after a two to ten-year follow up. Placing a stent across the vascular segment which has been dilated by PTA reduces the rate of restenosis.
During CEA, transcranial Doppler (TCD) monitoring studies have suggested that emboli may be responsible for half of the cerebrovascular complications of this procedure (Moore et al,
Stroke
26:188-201, 1995). A small study has compared TCD of the middle cerebral artery in patients undergoing CEA or PTA (Sundt et al,
Mayo Clin. Proc
. 50:301-306, 1975). CEA was associated with longer occlusion times and greater reductions in ipsilateral MCA velocity. In contrast thereto, PTA was associated with more micro-embolic signals.
There is an urgent need to develop specially designed medical devices to address the issues of post-angioplasty restenosis and to provide distal protection from thrombo-emboli during PTA. Stents and stent grafts whose size and compliance characteristics are uniquely suited for the carotid vasculature and the vertebro-basilar system both intra- and extracranially are still not commercially available and sorely needed. In addition, distal protection devices that allow continuous distal cerebral perfusion while preventing distal emboli would dramatically improve the safety and feasibility of luminal reconstruction in the cerebral vasculature.
Aneurysmal subarachnoid hemorrhage is a major cause of death and disability in a relatively young patient population. There is an annual incidence of aneurysmal subarachnoid hemorrhage of approximately 10-12 per 100,000 population in most western countries. In the United States nearly 40,000 individuals are hospitalized with aneurysms yearly (Wieber et al, 1992). The natural history of the disease is such that over 30% of patients will die within 24 hours of the bleed, and another 25-30% will succumb in the next four weeks without some form of intervention. As recently as 1993 the only therapeutic option for these patients was surgical management. In the United States, 55-65% of patients suffering aneurysmal subarachnoid hemorrhage do not receive surgical treatment due to their poor medical condition, advanced age, or other factors. This patient population is, instead, relegated to a conservative medical management regimen. The outcome for such non-surgical patients is dismal, with approximately 60% mortality and 25-40% morbidity reported within six months of the original bleed (Weir,
Aneurysms Affecting the Nervous System
, Chapter II, pp. 19-54, 1987).
Endovascular techniques for the treatment of intracranial aneurysms have been evolving over the past ten or fifteen years. Historically, the endovascular treatment of intracranial aneurysms has been fraught with significant intraoperative morbidity and mortality and poor clinical outcome. Endovascular occlusion has been attempted with a variety of materials from balloons to iron microspheres. The Guglielmi detachable coil, which has been in use in Europe since 1992 and in North America since 1991, provided a major technical advance. Endovascular treatment of intracranial aneurysms has been performed in approximately 4,000 patients worldwide with the Guglielmi detachable coil and has significantly improved the treatment modality by providing a technically safer and more reliable occlusion system.
Data from medical centers with significant endovascular experience suggest complication rates of aneurysm treatment following subarachnoid hemorrhage to be in the range of 1.5-5% mortality and 3-5% mor
Bose Arani
Nelson Peter Kim
Browdy and Neimark PLLC
Milano Michael J.
New York University
Roberts P
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