Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2000-04-25
2003-05-06
Casler, Brian L. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S004010, C604S008000, C604S027000, C604S035000, C604S184000
Reexamination Certificate
active
06558356
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 device capable of removing blood from a peripheral artery or symptomatic carotid artery and returning the blood to the contralateral carotid artery, thereby providing a means of augmenting the collateral vasculature and maintaining perfusion distal to the offending lesion. The device may employ neuroprotective agents, hypothermic perfusion, and an atherectomy device or 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. Outcome following stroke is influenced by a number of factors, the most important being the nature and severity of the resulting neurologic deficit. The patient's age, the cause of stroke, and coexisting medical illness also affect prognosis. Overall, less than 80% of patients with stroke survive for at least 1 month, and approximately 35% have been cited for the 10-year survival rates. Of patients who survive the acute period, up to 75% regain independent function, while approximately 15% require institutional care.
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 hemispheric 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 undergoing cardiothoracic surgery, 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. Effective stroke therapies therefore rely on the physicians' ability to respond to treatment quickly, since the longer the brain is deprived of blood flow, the greater the damage that occurs. The devices and methods of the present invention are used to augment contralateral blood flow across the Circle of Willis to improve and maintain perfusion to an ischemic region distal to an occluded intra/extracranial cerebral artery, and thus can be utilized in stroke patients immediately after onset of symptoms to maintain viability of the cerebral tissue until the obstructing lesion is removed by an intervention or resolved with time (more than one half of the occluding thrombi usually lyse themselves in a few days).
One embodiment of the medical device comprises first and second elongate tubes. Each tube has a manometer at a distal end and a lumen communicating with a port at the distal end. An expandable occlusive member is optionally mounted on either or both tubular members proximal to the distal port and is adapted to expand to engage the lumen of an intracranial or extracranial artery. A proximal end of each tubular member attaches to an oxygenator or a pump for aspirating blood through the first tube and perfusing the blood through the second tube.
In another embodiment, each tube has an additional lumen which communicates with a port distal to the balloon occluder for infusing fluid and pharmaceutical agents, such as a neuroprotective agent or heparin.
In still another embodiment, the first and second tubes are carried within the lumen
Casler Brian L.
CoAxia, Inc.
O'Melveny & Myers LLP
Thissell Jeremy
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