Do We Really Need Pulse? Chronic Nonpulsatile and Pulsatile Blood Flow: From the Exercise Response Viewpoints

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Abstract
The response of the body and the blood pump was evaluated in animals with a pulsatile artificial heart (total artificial heart [TAH]) and those with a nonpulsatile artificial heart (nonpulsatile biventricular bypass [NPBVB]) subjected to the same exercise load. The animals used in this study were 5 calves implanted with a pusher-plate type TAH (45-206 days) and 5 calves implanted with a nonpulsatile centrifugal pump (34-99 days). The pre-exercise pump flow rate was 92.1 +/- 8.1 ml/kg/min for the TAH group and 94.8 +/- 9.1 ml/kg/min for the NPBVB group, with no significant difference between the two groups. The workload was administered at a rate of 1.5 mph for 15 min. The artificial heart driving conditions were kept constant throughout the test period. Sequential changes in hemodynamic response and metabolism were determined before, during, and for 30 min after exercise. Both TAH and NPBVB calves showed excellent tolerance of the workload (1.5 mph exercise); in NPBVB calves, oxygen demand was compensated for by an increase in the arteriovenous oxygen difference during exercise; and norepinephrine showed a greater response in the NPBVB group. Based on the results presented, the nonpulsatile pump seems to lend itself to a mechanically driven artificial heart of the complete implantation type because of its small size, high efficiency, and the lack of need for a compliance chamber.