In Vitro Evaluation of an Immediate Response Starling-Like Controller for Dual Rotary Blood Pumps

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Stephens, Andrew F
Stevens, Michael C
Gregory, Shaun D
Kleinheyer, Matthias
Salamonsen, Robert F
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2017
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Rotary ventricular assist devices (VADs) are used to provide mechanical circulatory support. However, their lack of preload sensitivity in constant speed control mode (CSC) may result in ventricular suction or venous congestion. This is particularly true of biventricular support, where the native flow-balancing Starling response of both ventricles is diminished. It is possible to model the Starling response of the ventricles using cardiac output and venous return curves. With this model, we can create a Starling-like physiological controller (SLC) for VADs which can automatically balance cardiac output in the presence of perturbations to the circulation. The comparison between CSC and SLC of dual HeartWare HVADs using a mock circulation loop to simulate biventricular heart failure has been reported. Four changes in cardiovascular state were simulated to test the controller, including a 700 math formula reduction in circulating fluid volume, a total loss of left and right ventricular contractility, reduction in systemic vascular resistance ( math formula) from 1300 to 600 math formula, and an elevation in pulmonary vascular resistance ( math formula) from 100 to 300 math formula. SLC maintained the left and right ventricular volumes between 69–214 math formula and 29–182 math formula respectively, for all tests, preventing ventricular suction (ventricular volume = 0 math formula) and venous congestion (atrial pressures > 20 math formula). Cardiac output was maintained at sufficient levels by the SLC, with systemic and pulmonary flow rates maintained above 3.14 math formula for all tests. With the CSC, left ventricular suction occurred during reductions in SVR, elevations in PVR, and reduction in circulating fluid simulations. These results demonstrate a need for a physiological control system and provide adequate in vitro validation of the immediate response of a SLC for biventricular support.

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41
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10
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Biomedical engineering
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Clinical sciences
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