Demarcating fixed points in cardiac ventricles in the dog by catheter placement of tantalum coils has been shown to provide an excellent physiologic model. A new method emplying direct ventricular puncture has been developed for implanting these markers. The method has several advantages over an earlier peripheral catheter technique. Apical approach allows easier screw placement near the aortic and pulmonary valves. Peripheral vessels are left intact and pressure monitoring as well as contrast medium injection can be performed through the same catheter.