DEVELOPMENT OF A PIVOT BEARING SUPPORTED SEALLESS CENTRIFUGAL PUMP FOR VENTRICULAR ASSIST

Since 1991, in our laboratory, a pivot bearing-supported, sealless, ce ntrifugal pump has been developed as an implantable ventricular assist device (VAD). For this application, the configuration of the total pu mp system should be relatively small. The C1E3 pump developed for this purpose was anatomically compatible with the small-sized patient popu lation. To evaluate antithrombogenicity, ex vivo 2-week screening stud ies were conducted instead of studies involving an intracorporeally im planted VADs using calves. Five paracorporeal LVAD studies were perfor med using calves for longer than 2 weeks. The activated clotting time (ACT) was maintained at approximately 250 s using heparin. All of the devices demonstrated trouble-free performances over 2 weeks. Among the se 5 studies, 3 implantations were subjected to 1-month system validat ion studies. There were no device-induced thrombus formations inside t he pump housing, and plasma-free hemoglobin levels in calves were with in the normal range throughout the experiment (35, 34, and 31 days). T here were no incidents of system malfunction. Subsequently, the mass p roduction model was fabricated and yielded a normalized index of hemol ysis of 0.0014, which was comparable to that of clinically available p umps. The wear life of the impeller bearings was estimated at longer t han 8 years. In the next series of in vivo studies, an implantable mod el of the C1E3 pump will be fabricated for longer term implantation. T he pump-actuator will be implanted inside the body; thus the design ca lls for substituting plastic for metallic parts.