The present invention relates generally to devices and methods useful in treating patients with stroke or occlusive cerebrovascular disease. More specifically, the invention provides an extracranial device capable of reversing flow down a vertebral artery, an internal carotid artery, an external carotid artery and/or a common carotid artery, and into the subclavian artery during an invasive procedure, thereby avoiding distal embolization of vascular debris. Various diagnostic or therapeutic instruments, including an atherectomy catheter, a filter, and/or an angioplasty/stent catheter, can be introduced through the device for treating the occlusion. The invention may also be useful to reverse flow and pull back embolic debris during a stroke.
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. When a patient presents neurological symptoms and signs that 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.
Outcome following stroke is influenced by a number of factors, the most important being the nature and severity of the resulting neurologic deficit. 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. The extracranial or intracranial internal carotid artery, commonly affected by atherosclerosis causing symptomatic occlusion in the arterial lumen, is often responsible for hemispheric ischemic stroke and generating thromboembolic material downstream to the distal cerebral vessels. Treatment of the occluded carotid artery in patients with stroke and TIA or for stroke prevention in patients with asymptomatic flow limiting carotid stenosis includes performing angioplasty, stent placement, or atherectomy on the occluded carotid artery. This is also true of the vertebral artery. Unfortunately, placing instrumentation within a diseased artery is associated with increased risk of ischemic stroke, since manipulation of an atheromatous plaque in the arterial wall often causes emboli to dislodge distally in the narrow cerebral arteries.
Current methods of preventing distal embolization from carotid instrumentation include insertion of a blood filter distal to the occlusion and suctioning embolic debris during the procedures. Disadvantages associated with the conventional methods are that (1) inserting the filter through the atheromatous lesion is associated with increased risk of distal embolization, (2) using suction to reverse the flow in the internal carotid artery may increase a patient""s blood loss if the suctioned blood is discarded, and (3) systemic anticoagulation and pumping may be required to recycle the suctioned blood back into the arterial or venous system, and such anticoagulation is associated with increased risk of hemorrhage.
New devices and methods are thus needed for patients undergoing carotid procedures for definitive or prophylactic treatment of carotid plaque, which minimize the risk of distal embolization and prevent ischemic stroke.
The invention provides devices and methods for preventing ischemic stroke in patients undergoing percutaneous invasive vertebral or carotid procedures, including angioplasty, stent placement, and/or filter insertion, by reversing blood flow down a vertebral artery, an extracranial or intracranial internal carotid artery, an external carotid artery, and/or a common carotid artery and into the ipsilateral subclavian artery. In this way, embolic debris generated as a result of placing instrumentation within a diseased artery is diverted to the subclavian artery, thereby preventing stroke by minimizing distal embolization to the narrow cerebral vessels. The devices and methods are also useful to remove an embolus and improve flow (by reversing collateral blood flow across the circle of Willis) in patients with acute stroke.
The invention utilizes devices comprising a catheter having one or two expandable constricting members at its distal end. Each constrictor may be a balloon, in certain cases a toroidal balloon, or a device of any other appropriate shape, so that it can fully or partially occlude blood flow. The lumen of the catheter may be adapted for insertion of a therapeutic instrument, such as an angioplasty, atherectomy, and/or stent catheter. A manometer is optionally mounted proximal and/or distal to the constricting member for monitoring blood pressure proximal and/or distal the constrictor.
The occluder/constrictor is mounted near the distal. end of the catheter, in certain cases proximal to a port. Each balloon occluder and constrictor communicates with an inflation lumen and an inflation port at the proximal end of the catheter. In certain embodiments, the catheter will include first and second constriction/occlusion members. The second constrictor is mounted on a second member that is slideably insertable through the catheter, and passes beyond the first constrictor. In this way, the second member and the second constrictor are moveable longitudinally relative to the first constrictor. In other embodiments, the constrictor may consist of a balloon having more than one opening at its center for the passage of blood, or may consist of more than one expandable balloons allowing passage of blood through the gap between the arterial wall and the expanded balloons. The proximal end of the catheter may include a hemostatic valve.
In still another embodiment, the catheter includes a second lumen communicating with a proximal end and an infusion port at its distal end. The port is located distal to the distal port of the catheter. The second lumen and its port are adapted for delivering a pharmaceutical agent to the carotid, brachiocephalic and/or subclavian arteries, including an angiographic dye. Any device described in Barbut, U.S. Pat. No. 6,146,370, incorporated herein by reference in its entirety, may also be used in the methods described herein.
The invention provides methods for reversing flow in a vertebral or carotid artery having an atheromatous lesion. More specifically, the methods are useful in reversing flow down a vertebral artery, an extracranial or intracranial internal carotid artery, an external carotid artery, and/or a common carotid artery and into the subclavian artery. In a first method, using the devices described above, the distal end of the catheter is inserted into the right brachiocephalic artery. The catheter can be inserted over a guidewire through an incision on a peripheral artery, including the femoral artery, the subclavian artery, or the brachiocephalic artery. The catheter is positioned to locate the constricting member within the right brachiocephalic artery. Preferably, the constrictor is expanded to completely or partially occlude the right brachiocephalic artery. At a critically low brachiocephalic pressure distal to the constriction, blood flow in the carotid and vertebral arteries is reversed to pass over the atheromatous lesion and into the right subclavian artery. The flow reversal can be verified fluoroscopically with dye. If flow reversal fails to occur or if augmentation of flow reversal is desired, a second constricting member is expanded in the right subclavian artery, further reducing the pressure in the subclavian artery to facilitate reversal of flow down the carotid artery and into the subclavian artery.
In another method, the distal end of the catheter is inserted into the aorta in the takeoff of the left common carotid artery and left subclavian artery. The catheter is positioned to locate the constricting member within the inlet of the left subclavian artery and the left common carotid artery. The constrictor is expanded to completely or partially occlude the subclavian and common carotid artery. At a critically low pressure, blood flow in the carotid artery is reversed to pass over the atheromatous lesion and into the left subclavian artery. The flow reversal can be verified fluoroscopically with dye. If flow reversal fails to occur or if augmentation of flow reversal is desired, a second constricting member is expanded in the left subclavian artery, further reducing the pressure in the subclavian artery to facilitate reversal of flow down the carotid artery and into the subclavian artery.
In another method, using the device having a second occluder including a shunt for the passage of blood therethrough, the catheter is inserted in the right brachiocephalic artery, with the first occluder located in the right brachiocephalic artery and the second occluder located in the right subclavian artery. Preferably, the first occluder is expanded to occlude the brachiocephalic artery followed by expansion of the second occluder to occlude the subclavian artery. Alternatively, the second occluder is expanded to occlude the subclavian artery followed by expansion of the first occluder to occlude the brachiocephalic artery.
After blood reversal is confirmed, procedures on either the vertebral artery, the internal carotid artery or branches thereof (e.g., MCA or ACA), external carotid artery, or common carotid artery can be performed by advancing a therapeutic or diagnostic instrument through the lumen and port of the catheter distal to the occluder. An atherectomy catheter, for example, can be introduced to remove the atheroma in the right internal carotid artery without fear of distal embolization.
It will be understood that there are several advantages in using the devices and methods disclosed herein for prevention of distal embolization during use of instrumentation in the carotid arteries. For example, the devices (1) abolish the need for suction distal to the constricting/occluding member, thereby minimizing blood loss, (2) eliminate the need for systemic anticoagulation, pumping, and a second arterial or venous stick, all of which are required where suction is employed, (3) can be used to introduce a variety of diagnostic or therapeutic instrument to the carotid artery, (4) can be used in any procedures which require instrumentation within the carotid artery, (5) can be used for definitive treatment of acute or subacute ischemic stroke, (6) can be used in the angiogram or fluoroscopy suite available in most hospitals, (7) require only one incision site for entry, and (8) can be used to perform an interventional procedure without distal protection (e.g., a distal filter), and without crossing the lesion.