A catheter assembly for treatment of a stenosis in a lumen in a blood-carrying vessel comprising a first flexible elongate tubular member having proximal and distal extremities. A first inflatable balloon is coaxially mounted on the distal extremity of the first flexible elongate tubular member and has a main lumen and an aspiration lumen exiting through the distal extremity. A second flexible elongate tubular member has proximal and distal extremities and has a second inflatable balloon coaxially mounted on the distal extremity and has a blood perfusion lumen extending therethrough. The second flexible elongate tubular member is slidably mounted in the main lumen of the first flexible elongate tubular member. The first balloon is positioned so that it is adjacent to but proximal of the stenosis and is thereafter inflated to create a first occlusion in the lumen in the vessel. A negative pressure is created in the lumen in the vessel distal of the first balloon through the aspiration lumen. The second balloon is positioned distal of the stenosis and is inflated to create a second occlusion in the lumen of the vessel to form a working space between the first and second balloons which brackets the stenosis. Blood is perfused through the blood perfusion lumen distal of the second occlusion. A therapeutic procedure is performed in the working space.