Survey of mechanical assistance of the circulation and the present status of left-heart bypass.

The various types of mechanical circulatory assistance which recently have been developed are described. The techniques which appear to be most promising for clinical application are: veno-arterial bypass with oxygenation, synchronous arterial assistance, and closed-chest left-heart bypass.The effects of a left ventricular bypass on central hemodynamics and the oxygen requirements of the left ventricle are described. A bypass of 90% of the left ventricular output brings about a 30% reduction in the left ventricular myocardial oxygen requirement. Left atrial pressure is reduced. The central aortic mean pressure, the pulmonary artery pressure, and the right atrial pressure are not changed.