Rotary blood pumps increasingly are being used in open heart surgery and in assisted circulation for patients with heart disease. These rotary devices include vortex (centrifugal) and axial pumps, which can be utilized in conditions where the use of conventional pulsatile pumps would entail problems of cost and size. Rapid progress is now being made in developing new devices for controlling blood flow within the heart and great vessels as well as extracorporeally for use in coronary and intensiv