Two axial-flow Synergy Micro-Pumps as a biventricular assist device in an ovine animal model

OBJECTIVE: This study investigated the use of 2 Synergy Micro-Pumps for full biventricular assist device (BiVAD) support. We examined right-sided and left-sided hemodynamic parameters over a range of right-sided and left-sided pump speeds in an acute, fibrillating, non-beating-heart model in sheep. METHODS: Five juvenile sheep (43 +/- 2 kg) were implanted with two Synergy Micro-Pumps (CircuLite Inc, Saddle Brook, NJ), 1 in the right (RV) and 1 in the left ventricle (LV), through a median sternotomy. The RVAD outflow graft was anastomosed end-to-side to the pulmonary artery and the LVAD outflow to the ascending aorta. After surgical implantation of both pumps, ventricular fibrillation was induced and hemodynamic parameters were measured at 9 different levels of RVAD pump speed (from 20,000 to 28,000 rpm at 1,000-rpm increments), while the speed of the LVAD was set constant at 24,000, then at 26,000, and finally, at 28,000 rpm. RESULTS: At a fixed LVAD speed, RVAD and LVAD flow both increased identically as RVAD speed was increased. This was due to redistribution of blood volumes that resulted in resetting of pressure gradients across each pump and each vascular bed in a manner dictated by the pump pressure-flow characteristics. Results were similar with LVAD set at 24,000, 26,000, or 28,000 rpm. At the highest LVAD and RVAD speeds, flow averaged 3.1 +/- 0.7 liters/min, and pressures in the right atrium, pulmonary artery, left atrium, and aorta averaged 2.2 +/- 3.7, 24.4 +/- 6.5, 22.4 +/- 5.5, and 56.6 +/- 8.5 mm Hg, respectively. CONCLUSION: BiVAD support with the 2 Synergy Micro-Pumps is feasible and able to provide full hemodynamic support in sheep. This approach holds promise for providing biventricular partial support in humans and, in particular, for full support in small adults and children