Acute In Vivo Evaluation of an Implantable Continuous Flow Biventricular Assist System

Abstract

An implantable biventricular assist device offers a considerable opportunity to save the lives of patients with combined irreversible right and left ventricular failure. The purpose of this study was to evaluate the hemodynamic and physiologic performance of the combined implantation of the CorAide left ventricular assist device (LVAD) and the DexAide right ventricular assist device (RVAD). Acute hemodynamic responses were evaluated after simulating seven different physiological conditions in two calves. Evaluation was performed by fixing the speed of one individual pump and increasing the speed of the other. Under all conditions, increased LVAD or RVAD speed resulted in increased pump flow. The predominant pathophysiologic effect of independently varying DexAide and CorAide pump speeds was that the left atrial pressure was very sensitive to increasing RVAD speed above 2,400 rpm, whereas the right atrial pressure demonstrated much less sensitivity to increasing LVAD speed. An increase in aortic pressure and RVAD flow was observed while increasing LVAD speed, especially under low contractility, ventricular fibrillation, high pulmonary artery pressure, and low circulatory blood volume conditions. In conclusion, a proper RVAD-LVAD balance should be maintained by avoiding RVAD overdrive. Additional studies will further investigate the performance of these pumps in chronic animal models.

Introduction of fixed-flow mode in the DexAide right ventricular assist device

“…Based on our previous animal nonpulsatile perfusion studies using continuous-flow BVAD support of a fibrillated heart, it was shown that pulmonary circulation was maintained at 2 to 3 L/min with the RVAD pump off and the heart fibrillated 15. This residual flow may be explained by the presence of the so called “atrial kick”.…”

“…This BVAD control mode is particularly challenging as one must maintain proper right-left flow and atrial pressure balance. We have previously shown, in acute bovine BVAD experiments looking at the effects of varying levels of left and right ventricular support, the importance of adjusting the left pump speed and flow to be higher than that of the right pump and limiting the RVAD maximum operating speed to 2,400 rpm to avoid possible imbalance between right and left circulation 15. In our DexAide/CorAide BVAD control scheme, the CorAide pump is set to automatic mode, in which the pump speed is adjusted to obtain a target flow, while using the flow pulsatility to avoid possible left ventricular suction.…”

Biventricular Assist Devices: A Technical Review

“…68 However, the few documented clinical studies of rotary biventricular support warn of hemodynamic instability. 13,47,48,58,77 All report the importance of continued controller development to prevent pulmonary edema and incidence of suction events in the cannulated heart chamber. Clearly then, balancing of circuit volumes is crucial for any rotary support device, especially rotary BiVADs.…”

“…The CoreAide has a displacement volume of 84 mL, pump weight of 293 g, a portable power supply (6 h battery life), and controller weight of 1350 g. 58 It can achieve flow rates from 2 to 8 L min 21 and has an operational pump speed range of 2000-3000 RPM. Pumping 5 L min 21 against 100 mmHg, the CorAide LVAD uses less than 6 W of power at 2850 RPM.…”

Implantable Continuous-Flow Right Ventricular Assist Device: Lessons Learned in the Development of a Cleveland Clinic Device

“…CFBVAD support was investigated in our acute hemodynamic animal testing (CorAide CFLVAD and DexAide CFRVAD), in which we evaluated calf hemodynamics and physiologic response at baseline and for six different hemodynamic conditions of vasoconstriction, vasodilation, low circulating blood volume, and varying degrees of heart failure (35). The predominant pathophysiologic effect of independently varying DexAide and CorAide pump speeds was the marked sensitivity of left atrial pressure to increasing CFRVAD speed above 2,400 rpm.…”