Abstract: A surgical instrument includes a proximal actuation handle and a flexible guiding catheter having a channeling lumen, a suction lumen, and a control lumen. The guiding catheter has a slit opening into the control lumen at its distal end. A hollow cutting member extends through the channeling lumen and is moveable distally relative to the guiding catheter with a cutting actuation mechanism. The cutting member is preferably a section of thin walled hypodermic tubing having a sharpened distal end and is provided with a first proximal connector for coupling the cutting member to a first pressure regulator. A flexible control wire extends through the control lumen and is movable distally and rotatably relative to the guiding catheter with a control actuation mechanism. The control wire is sufficiently flexible to buckle with each contraction of the heart and has a foot at its distal end located beyond the distal end of the guiding catheter and movable relative thereto by movement of the control wire.