Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
2000-04-12
2001-11-06
Reip, David O. (Department: 3731)
Surgery
Instruments
Internal pressure applicator
C606S192000, C606S159000
Reexamination Certificate
active
06312444
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to medical devices useful in treating patients with acute stroke or occlusive cerebrovascular disease. More specifically, the invention provides an extra/intracranial balloon occlusive device with suction to remove a thrombus or embolus lodged in a cerebral vessel and a means of maintaining and augmenting perfusion of the collateral vasculature proximal to the offending lesion. The device may employ a chopping mechanism, vasodilator, hypothermic perfusion or local administration of t-PA and optionally an extracorporeal pumping mechanism to remove a vascular occlusion and reestablish cerebral perfusion.
BACKGROUND OF THE INVENTION
Stroke is the third most common cause of death in the United States and the most disabling neurologic disorder. Approximately 700,000 patients suffer from stroke annually. Stroke is a syndrome characterized by the acute onset of a neurological deficit that persists for at least 24 hours, reflecting focal involvement of the central nervous system, and is the result of a disturbance of the cerebral circulation. Its incidence increases with age. Risk factors for stroke include systolic or diastolic hypertension, hypercholesterolemia, cigarette smoking, heavy alcohol consumption, and oral contraceptive use.
Hemorrhagic stroke accounts for 20% of the annual stroke population. Hemorrhagic stroke often occurs due to rupture of an aneurysm or arteriovenous malformation bleeding into the brain tissue, resulting in cerebral infarction. The remaining 80% of the stroke population are ischemic strokes and are caused by occluded vessels that deprive the brain of oxygen-carrying blood. Ischemic strokes are often caused by emboli or pieces of thrombotic tissue that have dislodged from other body sites or from the cerebral vessels themselves to occlude in the narrow cerebral arteries more distally. When a patient presents with neurological symptoms and signs which resolve completely within 1 hour, the term transient ischemic attack (TIA) is used. Etiologically, TIA and stroke share the same pathophysiologic mechanisms and thus represent a continuum based on persistence of symptoms and extent of ischemic insult.
When a patient presents with neurological deficit, a diagnostic hypothesis for the cause of stroke can be generated based on the patient's history, a review of stroke risk factors, and a neurologic examination. If an ischemic event is suspected, a clinician can tentatively assess whether the patient has a cardiogenic source of emboli, large artery extracranial or intracranial disease, small artery intraparenchymal disease, or a hematologic or other systemic disorder. A head CT scan is often performed to determine whether the patient has suffered an ischemic or hemorrhagic insult. Blood would be present on the CT scan in subarachnoid hemorrhage, intraparenchymal hematoma, or intraventricular hemorrhage.
Traditionally, emergent management of acute ischemic stroke consists of mainly general supportive care, e.g. hydration, monitoring neurological status, blood pressure control, and/or anti-platelet or anti-coagulation therapy. In June 1996, the Food and Drug Administration approved the use of Genentech Inc.'s thrombolytic drug, tissue plasminogen activator (t-PA) or Activase®, for treating acute stroke. In a randomized, double-blind trial, the National Institute of Neurological Disorders and t-PA Stroke Study, there was a statistically significant improvement in stoke scale scores at 24 hours in the group of patients receiving intravenous t-PA within 3 hours of the onset of an ischemic stroke. Since the approval of t-PA, an emergency room physician could, for the first time, offer a stroke patient an effective treatment besides supportive care.
However, treatment with systemic t-PA is associated with increased risk of intracerebral hemorrhage and other hemorrhagic complications. Patients treated with t-PA were more likely to sustain a symptomatic intracerebral hemorrhage during the first 36 hours of treatment. The frequency of symptomatic hemorrhage increases when t-PA is administered beyond 3 hours from the onset of a stroke. Besides the time constraint in using t-PA in acute ischemic stroke, other contraindications include the following: if the patient has had a previous stroke or serious head trauma in the preceding 3 months, if the patient has a systolic blood pressure above 185 mm Hg or diastolic blood pressure above 110 mmHg, if the patient requires aggressive treatment to reduce the blood pressure to the specified limits, if the patient is taking anticoagulants or has a propensity to hemorrhage, and/or if the patient has had a recent invasive surgical procedure. Therefore, only a small percentage of selected stroke patients are qualified to receive t-PA.
New devices and methods are thus needed in treating patients with acute ischemic stroke and occlusive cerebrovascular disease, in treating symptomatic patients with embolization or hemodynamic compromise, or in stroke prevention, e.g., patients with incidental finding of asymptomatic carotid lesion, which improve a patient's neurological function and quality of life without causing significant side effect, and can be used in patients with contraindication to using t-PA.
SUMMARY OF THE INVENTION
The invention provides devices and methods for treatment of acute ischemic stroke and occlusive cerebrovascular disease by taking advantage of the collateral cerebral circulation. Anastomoses between the cerebral arteries provide alternative pathways in which blood can reach a given region of the brain besides the predominant supplying artery. At the base of the brain close to the sella turcica, circulus arteriosus cerebri, or circle of Willis, connects the vertebral and internal carotid arteries to each other and to the vessels of the opposite side. When occlusion of a blood vessel interrupting the flow of blood to a specific region of the brain occurs, survival of the brain tissue and therefore severity of a patient's neurological deficit depend on the number and size of its collateral arteries. The devices of the present invention utilize pressure generated by collateral cerebral circulation to facilitate removal of thromboembolic material in an occluded carotid or cerebral artery.
A first embodiment of the medical device comprises an elongate catheter, a balloon occluder, and a chopping mechanism. The catheter has a proximal end, a distal end and a lumen which communicates with an aspiration port at the distal end. The balloon occluder, which communicates with an inflation lumen and may comprise an elastomeric balloon, is mounted on the distal end of the catheter proximal to the aspiration port. The chopping mechanism is operated to chop away any particulate matter engaged by suction through the aspiration port.
In another embodiment, the catheter has an additional lumen which communicates with a port distal to the balloon occluder for infusing blood and pharmaceutical agents, such as a vasodilator or t-PA. Vasodilator, such as nifedipine or nitroprusside, is used to reverse any vascular spasm which occurs as a result of instrumentation. The chopping mechanism may comprise an abrasive grinding surface or a rotatable blade which operates within a housing, as described in Barbut et al., U.S. Pat. No. 5,662,671, incorporated herein by reference in its entirety.
In still another embodiment, the catheter includes a perfusion lumen which communicates with one or a plurality of perfusion ports and is adapted for infusion of oxygenated blood. The perfusion ports may be located on two cylindrical members which can be rotated relative to each other so that maximum blood flow through the catheter is achieved when the perfusion ports on the two members are aligned. Alternatively, the two cylindrical members can be rotated so that the perfusion ports on the two members are partially aligned to limit blood flow, or completely misaligned to achieve no blood flow. In this manner, the flow rate of blood or fluid through the perfusion ports can be
Coaxia, Inc.
Lyon & Lyon LLP
Ngo Lien
Reip David O.
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