METHODS OF PLACING LARGE BORE ASPIRATION CATHETERS

1 . A method of removing a vascular obstruction, comprising the steps of:

transvascularly advancing a distal end of an aspiration catheter into proximity with an obstruction;

activating a low flow, detection mode of aspiration through the catheter; and

thereafter activating a momentary control to activate a high flow, aspiration mode of operation and draw obstructive material into the distal end of the access catheter.

2 . A method of removing a vascular obstruction as in claim 1 , wherein activating the momentary control enlarges a restriction in a flow path between the aspiration catheter and a source of vacuum.

3 . A method of removing a vascular obstruction as in claim 1 , comprising advancing the distal end of the aspiration catheter into proximity with a pulmonary embolism.

4 . A method of removing a vascular obstruction as in claim 1 , comprising advancing the distal end of the aspiration catheter into proximity with a deep vein thrombosis.

5 . A method of removing a vascular obstruction as in claim 1 , comprising advancing the distal end of the aspiration catheter into proximity with a peripheral arterial occlusion.

6 . A flow control for an aspiration catheter, comprising:

a housing, defining a central cavity, and having a patient port, a manifold port and a filter port; a movable gate within the housing having a flow path and configured to selectively place the patient port in communication with the filter port, the patient port in communication with the manifold port or the manifold port in communication with the filter port.

7 . A flow control as in claim 6 , wherein the movable gate comprises a cylindrical body having a first port in communication with a second port by a flow path through the body.

8 . A flow control as in claim 7 , wherein the first port, the second port and a solid side wall are spaced about 120 degrees apart around the circumference of the gate.

9 . An aspiration catheter, comprising:

an elongate, flexible tubular body, having a proximal end, a distal end and a central lumen;

a hemostasis valve on the proximal end of the catheter, the hemostasis valve comprising:

a collapsible tubular sidewall defining a valve lumen in communication with the central lumen;

a filament formed into a loop around the tubular sidewall, the filament having at least a first tail portion extending away from the loop and connecting to a first lever; and

a first spring configured to move the first lever in a direction that pulls the first tail portion away from the tubular sidewall, reducing the diameter of the valve lumen in response to reducing the diameter of the loop.

10 . An aspiration catheter as in claim 9 , wherein the filament further comprises a second tail portion extending between the loop and a second lever.

11 . An aspiration catheter as in claim 10 wherein the first and second levers are biased in a direction that places the first and second tail portions under sufficient tension to reduce the diameter of the central lumen and provide a seal around a secondary device extending through the valve.

12 . An aspiration catheter as in claim 10 wherein the first and second levers are biased in a direction that places the first and second tail portions under sufficient tension to close the valve.

13 . A method of placing a catheter comprising:

advancing a catheter and cannulated dilator over a guidewire to an intravascular site;

removing the dilator while leaving the catheter and guidewire in place;

wherein the removing step comprises pulling a proximal portion of the dilator laterally off of the guidewire with the guidewire progressively passing through an axially extending split in the dilator.

14 . A method as in claim 13 , further comprising the step of unlocking the dilator from the catheter prior to the removing step.