Aspiration method

Details Aspiration method Aspiration method

2002-08-05

2004-10-19

Casler, Brian L. (Department: 3763)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S510000, C604S096010

Reexamination Certificate

active

06805692

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved method for aspirating emboli, thrombi, and other types of particles from the human arterial or venous system, the method being particularly well suited for treating stenoses or occlusions within saphenous vein grafts, coronary arteries, arteries above the aortic arch such as the carotid and cerebral arteries, and similar vessels.
2. Description of the Related Art
Human blood vessels often become occluded or completely blocked by plaque, thrombi, other deposits, emboli or other substances, which reduce the blood carrying capacity of the vessel. Should the blockage occur at a critical place in the circulatory system, serious and permanent injury, or even death, can occur. To prevent this, some form of medical intervention is usually performed when significant occlusion is detected.
Coronary heart disease is an extremely common disorder in developed countries, and is the leading cause of death in the U.S. Damage to or malfunction of the heart is caused by narrowing or blockage of the coronary arteries (atherosclerosis) that supply blood to the heart. The coronary arteries are first narrowed and may eventually be completely blocked by plaque, and may further be complicated by the formation of thrombi (blood clots) on the roughened surfaces of the plaques. Myocardial infarction can result from atherosclerosis, especially from an occlusive or near occlusive thrombi overlying or adjacent to the atherosclerotic plaque, leading to death of portions of the heart muscle. Thrombi and emboli also often result from myocardial infarction, and these clots can block the coronary arteries, or can migrate further downstream, causing additional complications.
Various types of intervention techniques have been developed which facilitate the reduction or removal of the blockage in the blood vessel, allowing increased blood flow through the vessel. One technique for treating stenosis or occlusion of a blood vessel is balloon angioplasty. A balloon catheter is inserted into the narrowed or blocked area, and the balloon is inflated to expand the constricted area. In many cases, near normal blood flow is restored. It can be difficult, however, to treat plaque deposits and thrombi in the coronary arteries, because the coronary arteries are small, which makes accessing them with commonly used catheters difficult.
Other types of intervention include atherectomy, deployment of stents, introduction of specific medication by infusion, and bypass surgery. Each of these methods are not without the risk of embolism caused by the dislodgement of the blocking material which then moves downstream. In addition, the size of the blocked vessel may limit percutaneous access to the vessel.
In coronary bypass surgery, a more costly and invasive form of intervention, a section of a vein, usually the saphenous vein taken from the leg, is used to form a connection between the aorta and the coronary artery distal to the obstruction. Over time, however, the saphenous vein graft may itself become diseased, stenosed, or occluded, similar to the bypassed vessel. Atherosclerotic plaque in saphenous vein grafts tends to be more friable and less fibrocalcific than its counterpart in native coronary arteries.
Diffusely diseased old saphenous vein grafts with friable atherosclerotic lesions and thrombi have therefore been associated with iatrogenic distal embolic debris. Balloon dilatation of saphenous vein grafts is more likely to produce symptomatic embolization than dilatation of the coronary arteries, not only because of the difference in the plaque but also because vein grafts and their atheromatous plaques are generally larger than the coronary arteries to which they are anastomosed. Once the plaque and thrombi are dislodged from the vein, they can move downstream, completely blocking another portion of the coronary artery and causing myocardial infarction. In fact, coronary embolization as a complication of balloon angioplasty of saphenous vein grafts is higher than that in balloon angioplasty of native coronary arteries. Therefore, balloon angioplasty of vein grafts is performed with the realization that involvement by friable atherosclerosis is likely and that atheroembolization represents a significant risk.
Because of these complications and high recurrence rates, old diffusely diseased saphenous vein grafts have been considered contraindications for angioplasty and atherectomy, severely limiting the options for minimally invasive treatment. However, some diffusely diseased or occluded saphenous vein grafts may be associated with acute ischemic syndromes, necessitating some form of intervention.
There is therefore a need for improved methods of treatment for occluded vessels such as saphenous vein grafts and the smaller coronary arteries, the carotid and cerebral arteries, which decrease the risks to the patient.
SUMMARY OF THE INVENTION
The present invention provides a novel method for removing plaque, thrombi, emboli and other types of obstructions or occlusions from blood vessels having an inlet fluid pressure of at least 0.2 psi at any time during the diastolic/systolic cycle of the heart. Although the pressure within the vessel may fall below 0.2 psi during relaxation between heartbeats, so long as the pressure created by the heartbeat rises to at least 0.2 psi, the pressure within the vessel will be sufficient. The method preferably includes the use of an occlusive device such as a balloon or filter to occlude the vessel distal to the obstruction, an optional therapy catheter to treat the obstruction, and a source of aspiration to remove the debris created by the therapy. By utilizing the fluid pressure and flow within the blood vessel, this method eliminates the need for a separate irrigation catheter and irrigation fluid. The present invention allows for the removal of occlusions more rapidly than known methods. Speed is essential in such procedures, since blood flow is significantly decreased or stopped during the time the vessel is occluded. The speed with which normal blood flow is restored is more critical in main vessels which supply blood to collateral vessels. The method of the present invention allows for the removal of occlusions from saphenous vein grafts, coronary arteries, arteries above the aortic arch such as the carotid and cerebral arteries, and blood vessels of similar pressure. The minimally invasive treatment can be provided at low cost and at relatively low risk to the patient.
In accordance with one aspect of the present invention, there is provided a method for the treatment of a stenosis or an occlusion in a blood vessel having a fluid pressure of at least about 0.2 psi. The blood vessel can be a saphenous vein graft, a coronary artery, a blood vessel above the aortic arch, or any other vessel with a fluid flow rate of at least about 10 cc per minute (prior to occlusion of the vessel using an occlusive device as described below), and more preferably, about 60 to 80 cc per minute, or about 120 to 140 cc per minute. This flow rate is needed to provide adequate irrigation fluid, which allows for substantially complete aspiration of the area surrounding the occlusion in a very short period of time. Using this combination of irrigation provided from the blood flow into the vessel and aspiration, it has been found that aspiration of debris and fluid within the working area can occur in less than 3 seconds, but can also continue for 10 to 20 seconds or longer, until the procedure is completed. Thus, the physician can quickly and efficiently clear the debris from the area and restore normal blood flow through the vessel.
One aspect of the method comprises first inserting a catheter or guidewire having an occlusive device at its distal end into the blood vessel, until it is distal to the stenosis or occlusion. It is to be understood that the stenosis or occlusion could be in a discrete location or diffused within the vessel. Therefore, although placement of the occlusive device is said to be distal to

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