Key result
Jarvik artificial ventricles yielded a theoretical cardiac output comparable to the natural heart, indicating that inflow resistance is not a limiting factor.
In vitro testing demonstrates that inflow resistance does not limit the cardiac output of Jarvik artificial ventricles, pointing to valvular regurgitation as the likely cause of suboptimal performance.
Supports excluding inflow resistance as a design constraint; leaves open regurgitation's role and in vivo translation.
The pneumatic total artificial heart has been assumed to be inflow limited. Mock circulation studies on the Jarvik-5 and Jarvik-7 artificial ventricles seemed to support this assumption because a Starling's response comparable to the natural heart was not achieved. Unfortunately, mock circulation studies do not separate the effects of valvular regurgitation from inflow resistance. By using a simple filling tank, filling times were determined for the Jarvik ventricles that were a function of inflow resistance alone. Theoretical maximum cardiac outputs based on these inflow resistance-dependent filling times were then calculated. For filling pressures around 5 mmHg and under modest diastolic vacuum of 5 cm H2O, the Jarvik ventricles yield a theoretical cardiac output as good as the natural heart's. Thus, inflow resistance is not a limiting factor and valvular regurgitation is left as the most likely cause of a less than optimal Starling's response on mock circulation and in vivo.
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Lioi et al. (1981) studied this question. Jarvik-5 and Jarvik-7 artificial ventricles vs. Natural heart was evaluated on Theoretical maximum cardiac output. Jarvik artificial ventricles yielded a theoretical cardiac output comparable to the natural heart, indicating that inflow resistance is not a limiting factor.
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