A guiding catheter used for coronary angioplasty procedures includes an plurality of ports in the wall of the guiding catheter. A moveable member is disposed in the lumen or wall of the guiding catheter and is selectively movable between a first position blocking the ports and a second position not blocking the ports. The moveable member is shown as an elongated stylet, a hollow tube with matching ports or a plurality of inflatable balloons. The catheter is positioned adjacent to an artery to be examined. The ports are blocked by the moveable member while contrast medium is injected through the guide catheter to the artery. The ports are opened otherwise to enable the flow of blood between the catheter and the artery.