Response of Rotary Blood Pumps to Changes in Preload and Afterload at a Fixed Speed Setting Are Unphysiological When Compared With the Natural Heart

Abstract

Responses of four rotary blood pumps (Incor, Heartmate II, Heartware, and Duraheart) at a single speed setting to changes in preload and afterload were assessed using the human left ventricle as a benchmark for comparison. Data for the rotary pumps were derived from pressure flow relations reported in the literature while the natural heart was characterized by the Frank-Starling curve adjusted to fit outputs at different afterloads reported in the literature. Preload sensitivity (mean ± SD) for all pumps at all afterloads tested was 0.105 ± 0.092 L/min/mm Hg, while afterload sensitivity was 0.09 ± 0.034 L/min/mm Hg-values that were not significantly different (t-test, P = 0.56). By contrast, preload sensitivity of the natural heart was over twice as high (0.213 ± 0.03 L/min/mm Hg) and afterload sensitivity about one-third (0.03 ± 0.01 L/min/mm Hg) the values recorded for rotary pumps (t-test, P < 0.001). Maximum preload sensitivity and minimum afterload sensitivity allow the right and left ventricles to synchronize outputs without neural or humoral intervention. This theoretical study reinforces the need to provide preload sensitive control mechanisms of sufficient power to enable the pump and left ventricle in combination to adapt to changes in right ventricular output automatically.

Blood Pressure and Adverse Events During Continuous Flow Left Ventricular Assist Device Support

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Continuous Flow Left Ventricular Assist Devices: Shared Care Goals of Monitoring and Treating Patients

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In Vivo Testing of a Novel Blood Pump for Short-Term Extracorporeal Life Support

“…These pumps operate at a fixed rotational speed, requiring manual adjustments to accommodate the rapid fluctuations in intravascular volume status that can be seen in critically ill patients. They are sensitive to variations in afterload, resulting in potentially undesired changes in flow (1). There is also the concern for cavitation and hemolysis due to excessive negative pressure (2).…”