Embolism remains a significant complication of the total artificial heart (TAH). The ineffectual deairing of the TAH can allow embolization of the retained air. The standard needle aspiration of TAH air (Group A) was compared with a new protocol (Group B) that included standard needle TAH aspiration plus simultaneous pumping of the TAH against an occluded ascending aorta and main pulmonary artery with vacuum applied to a needle in the proximal aorta and pulmonary artery. There were 4 calves in each group. There was no premortem evidence of systemic or pulmonary emboli. Both groups of animals were electively terminated less than 2 weeks postoperatively. Postoperative mean aortic and pulmonary artery pressures were recorded for each animal. Animals in Group B had a significant decline in pulmonary artery pressures (43 & 12 vs. 33 & 8 mm Hg) 1 h after TAH implantation when compared with Group A. All other aortic and pulmonary artery pressure differences between Groups A and B were not statistically significant within 24 h of the operation. Group A animals had a 75% incidence, and Group B animals had 100% incidence of TAH thrombus. This very small thrombus was found exclusively at the inflow valve-TAH housing interface. Evaluation of the kidneys postmortem was used to identify embolic injury. All animals in Group A had evidence of acute, hemorrhagic injury, but none of the Group B animals had similar injury. Half of the animals in each group had small, fibrotic chronic renal cortical injury, which did not develop during TAH implantation. The more vigorous deairing protocol (Group B) significantly decreased early postoperative pulmonary hypertension. The absence of acute hemorrhagic renal injuries appeared to be associated with improved TAH deairing. Chronic renal injuries were not associated with the TAH, which makes them poor indicators of TAH emboli. Improved TAH deairing can provide