The authors made a study on a new left atrium-aorta bypass method employing an assist heart pump having an accessory chamber with a capacity of 40ml. With this heart pump having an accessory chamber, the negative pressure to the atrial side was reduced and favorable sensitivity against the atrial pressure was demonstrated also in the mock circulation. Further, by making the length of the left atrium cannula as short as possible and by increasing the diameter of the cannula, suction was facilitated and thrombus formation was reduced. Thus it was possible to extend the survival period to 48 days in our long term chronic experiment. In the 40 cases of left atrium-aorta bypass performed from 1974 to 1976, the results were very pessimistic, but with the improvement made on the left atrium cannula and the revision made in the driving method, especially in the movement of the accessory chamber membrane, it was confirmed that this new method was effective from the standpoint of hemodynamics and prevention of thrombus formation.
