RESULTS OF CHRONIC ANIMAL-EXPERIMENTS WITH A NEW VERSION OF A MAGNETICALLY SUSPENDED CENTRIFUGAL PUMP

We have developed a magnetically suspended centrifugal pump (MSCP) for long-term ventricular support. This study reports results of chronic animal experiments using a new version of the MSCP. Three sheep weighi ng 50-70 kg were used in this study. A left heart assist system was es tablished with cannulas into the descending aorta and the left ventric ular apex. In two sheep the MSCP was positioned outside the body and i n one sheep implanted on the chest wall. The pumping flow was estimate d by the motor current and motor speed. The temperature of the pump an d the muscle near the pump was recorded for 10 days after operation. T he duration of continuous pumping was 60, 140, and 230 days+ (ongoing) , respectively. The cause of termination was infection associated with thrombus formation in the first, and failure of magnetic suspension i n the second sheep. No thrombus or embolus was observed after sacrific e of the second sheep. The third sheep has been going well despite ski n necrosis around the pump pocket. The estimation of pumping flow was reliable even at 140 days. Temperature of the pump surface was 42 degr ees C immediately after the operation and gradually reduced to 41 degr ees C. The MSCP is a reliable pump for long-term circulatory assist.