Chronic evaluation of a compact nonseal magnet pump as a nonpulsatile pump for long-term use

Use of a nonpulsatile pump is one of the most interesting approaches in the development of artificial hearts. A centrifugal pump without a seal around the rotating part was evaluated in five goats. The size of the pump is 8.4 cm x phi 7.0 cm, including an electric motor. A polypropylene impeller with four fins on the top of a column in which a magnetic ring is embedded spins by coupling with a rotating magnet outside the housing. In the goats, the pump was placed paracorporeally to provide total left heart bypass at a flow rate of 4.6-7.6 L/min, and activated clotting time was controlled at 200-300 sec by continuous heparin infusion. Although the first three goats died within 3 days due to bleeding, embolism, and a jammed impeller, respectively, a pump could be driven for 14 days in the fourth goat, and another pump with a rotational control feedback system ran for 32 days in the fifth goat. Plasma free hemoglobin levels were 13.8 +/- 4.3 mg/dl and 9.5 +/- 2.5 mg/dl, and platelet counts were 53.8 +/- 24.7 x 10(4)/mm3 and 62.0 +/- 22.0 x 10(4)/mm3 after 12 hours and 7 days pumping, respectively. No thrombus was observed in the blood chamber in the last two cases. In conclusion, this pump has possibilities as a nonpulsatile pump for long-term use.