Intravascular device and method of manufacture and use

Abstract

An intravascular device and method of constructing an intravascular device. The device has a proximal portion which is stiffer than a distal portion. The device of the present invention may also be advanced through small vessels without the aid of a guidewire although a guidewire may be used when necessary. The device may be manufactured in a number of different ways and a preferred method is to use an expanded PTFE liner at the distal portion and an etched PTFE liner along the proximal portion. The device also has a number of different jacket sections, preferably at least four, with increasing durometer towards the proximal end and a braided section with varying pic along the length.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS [0001] The present application is a continuation-in-part of application Ser. No. 09 / 311,903, filed May 14, 1999, which is a continuation-in-part of application Ser. No. 09 / 243,578, filed Feb. 3, 1999, which is a continuation-in-part of application Ser. No. 09 / 018,214, filed of Feb. 3, 1998, the full disclosures of which are incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] The present invention relates generally to intravascular devices and methods. Intravascular devices are used to access various areas of the vasculature for a variety of reasons. Such devices are used to deliver and withdraw fluids and to deliver other devices such as stents, angioplasty balloons and thrombolytic devices. [0003] A specific application of the present invention is for treating acute arterial ischemia in areas such as the brain. The devices and methods of the present invention are particularly useful in connection with the devices and methods ...

AI Technical Summary

Benefits of technology

[0012] A particular advantage of the present invention lies in the ability to lessen or eliminate reperfusion injury which can result from the rapid restoration of full blood flow and pressure to ischemic tissue. As described above, the use of thrombolytics and other prior treatments can cause the abrupt removal of an obstruction causing rapid infusion of blood into the ischemic tissue downstream of the occlusion. It is believed that such rapid restoration of full blood flow and pressure, typically at normal physiologic pressures, can result in further damage to the leaky capillary beds and dysfunctional blood-brain barrier which results from the prior ischemic condition.

[0013] The present invention allows for a controlled reperfusion of the ischemic tissue where blood can initially be released downstream of the obstruction at relatively low pressures and / or flow rates. That is, it will be desirable to initiate the flow of blood or other oxygenated medium slowly and allow the flow rate and pressure to achieve their target values over time. For example, when actively pumping the oxygenated medium, the pumping rate can be initiated at a very low level, typically less than 30 cc / min, often less than 10 cc / min, and sometimes beginning at essentially no flow and can then be increased in a linear or non-linear manner until reaching the target value. Rates of increase can be from 1 cc / min / min to 360 cc / min / min, usually being from 5 cc / min / min to 120 cc / min / min. Alternatively, the flow of blood or other oxygenated medium can be regulated based on pressure as mentioned above. For example, flow can begin with a pressure in the previously ischemic bed no greater than 10 mmHg, typically from 10 mmHg to 70 mmHg. The pressure can then be gradually increased, typically at a rate in the range from 5-100 mmHg over 2, 8 or even 48 hours. In some instances, it may be desirable to employ blood or other oxygenated medium that has been superoxygenated, i.e., carrying more oxygen per ml than normally oxygenated blood.

[0014] While pumping will usually be required to achieve and / or maintain adequate perfusion, in some instances passive perfusion may be sufficient. In particular, perfusion of the smaller arteries within the cerebral vasculature can sometimes be provided using a perfusion conduit having inlet ports or apertures on a proximal portion of the conduit and outlet ports or apertures on a distal portion of the conduit. By then positioning the inlet and outlet ports on the proximal and distal sides of the obstruction, respectively, the natural pressure differential in the vasculature will be sufficient to perfuse blood through the conduit lumen past the obstruction. Usually, the inlet ports on the perfusion conduit will be positioned at a location as close to the proximal side of the occlusion as possible in order to minimize the length of perfusion lumen through which the blood will have to flow. In some instances, however, it may be necessary to position the inlet ports sufficiently proximal to the occlusion so that they lie in a relatively patent arterial lumen to supply the necessary blood flow and pressure. The cross-sectional area of the perfusion lumen will be maintained as large as possible from the point of the inlet ports to the outlet ports. In this way, flow resistance is minimized and flow rate maximized to take full advantage of the natural pressure differential which exists.

[0015] While perfusion is maintained through the perfusion conduit, treatment of the blood vessel blockage may be effected in a variety of ways. For example, thrombolytic, anticoagulant and / or anti-restenotic agents, such as tissue plasminogen activator (tPA), streptokinase, urokinase, heparin, or the like, may be administered to the patient locally (usually through the perfusion catheter) or systemically. In a preferred aspect of the present invention, such thrombolytic and / or anticoagulant agents may be administered locally to the arterial blockage, preferably through a lumen in the perfusion catheter itself. Such local administration can be proximal to the thrombus or directly into the thrombus, e.g., through side infusion ports which are positioned within the thrombus while the perfusion port(s) are positioned distal to the thrombus. Optionally, a portion of the blood which is being perfused could be added back to or otherwise combined with thrombolytic and / or anticoagulant agent(s) being administered through the catheter. The addition of blood to certain thrombolytic agents will act to augment the desired thrombolytic activity. The availability of the autologous blood being perfused greatly facilitates such addition. It would also be possible to deliver the agent(s) through the same lumen and distal port(s) as the blood being pumped back through the perfusion lumen so that the agents are delivered distally of the catheter. The latter situation may be used advantageously with neuroprotective agents, vasodilators, antispasmotic drugs, angiogenesis promoters, as well as thrombolytics, anticoagulants, and anti-restenotic agents, and the like. The two approaches, of course, may be combined so that one or more agents, such as thrombolytic agents, are delivered directly into the thrombus while neuroprotective or other agents are delivered distally to the thrombus. Moreover, such delivery routes can also be employed simultaneously with systemic delivery of drugs or other agents to the patient.

[0016] Alternatively or additionally, mechanical interventions may be performed while the vasculature is being perfused according to the present invention. For example, a perfusion conduit may have a very low profile and be used as a guide element to introduce an interventional catheter, such as an angioplasty catheter, an atherectomy catheter, a stent-placement catheter, thrombus dissolution device, or the like.

[0017] The perfusion of the oxygenated medium may be performed for a relatively short time in order to relieve ischemia (which may be advantageous because of damaged capillaries and / or blood-brain barrier) while other interventional steps are being taken, or may be performed for a much longer time either in anticipation of other interventional steps and / or while other long-term interventions are being performed. In particular, when thrombolytic and / or anticoagulant agents are being used to treat the primary blockage, the perfusion can be continued until the blockage is substantially relieved, typically for at least thirty minutes, often for four to eight hours, or even 2-3 days. In other instances, perfusion can be maintained for much longer periods, e.g., more than one week, more than two weeks, more than a month, or even longer. In some cases, it may even be desirable to maintain perfusion and placement of the perfusion conduit for an extended period of time with the patient having a portable or implantable pump coupled to the conduit. The pump may also have a reservoir for delivery of therapeutic agents and may be implanted or carried on a belt or the like.

Problems solved by technology

It will generally be undesirable to expose the vasculature distal to the occlusion to a pressure above that to which it has been exposed prior to the occlusion.

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