Design mediated thrombus reduction in the Utah-100 total artificial heart. The Utah-100 total artificial heart was initially designed and tested in 1983. General design goals, including improved fit for human application, improved reliability, and elimination of thrombus formation, were identified as improvements over the clinically used Jarvik-7 artificial heart, previously developed at the Institute for Biomedical Engineering, University of Utah. Specific design goals included 1) elimination of connector and valve-associated thrombus formation and 2) elimination of gross mineralization, thrombus formation, and creases on the blood-pumping diaphragm of the device. Explant retrieval results from 29 calves and sheep implanted with the Jarvik-7 artificial heart were compared with results from 25 calves and sheep implanted with the Utah-100 artificial heart. Macroscopic thrombus formation was found in 44% of the connectors of the Jarvik-7 artificial-hearts, compared with 2% (p less than or equal to 0.01) in animals with the Utah-100 artificial heart. Subvalvular and supravalvular thrombi were observed in 33% of the valves in the Jarvik-7 artificial heart and 10% (p less than or equal to 0.01) of the valves in the Utah-100 artificial heart. Mineralization of the pumping diaphragm was observed in 12% of the animals implanted with the Jarvik-7 artificial heart and in 4% of the animals with the Utah-100 diaphragms. Thrombus formation in the diaphragm-housing interface occurred in 2% of Jarvik-7 ventricles and in 6% of the Utah-100 ventricles. There were no identifiable diaphragm creases in the Utah-100 diaphragms, but a 10% incidence was found in Jarvik-7 devices. These results validate substantial progress toward improved design and fabrication methods in the Utah-100 total artificial heart. 