COMPARATIVE ANALYSIS OF CARDIAC ENERGETICS IN ISOLATED HEARTS SUPPORTED BY PULSATILE OR ROTARY BLOOD PUMPS – IMPLICATIONS FOR CARDIAC RECOVERY?

Functional myocardial recovery during support with left ventricular assist devices (LVADs) is highly desirable but only observed in approx. 1% of all patients. Previously, the more frequently implanted pulsatile blood pumps (PBPs) showed higher recovery rates than the currently used rotary blood pumps (RBPs). The aim of this study was to comparatively assess the capability of PBPs and RPBs to unload the left ventricle and restore physiological cardiac energetics in isolated hearts. An RBP (Medtronic HVAD) and a heartbeat synchronized PBP (BerlinHeart Excor) were alternately connected to eight isolated porcine hearts. To modulate the mode of LVAD support, RBP rotational speed was set to different support levels and ejection delay of the PBP was phased from 0% to 90%. Pressures, flows, left ventricular volumes, and myocardial oxygen consumption were recorded and cardiac efficiency quantified by the ratio of external work (EW) over myocardial oxygen consumption. With increasing RBP support, lower left atrial pressures (LAP) were found to coincide with a decreased cardiac efficiency (r=0.91±0.12) with a median [inter quartile range] slope of 0.28 [0.91] %/mmHg. In contrast, depending on the phase delay of ejection of a PBP, LAP and cardiac efficiency follow a sinusoidal course with the LAP minimum at 90% and efficiency maximum at 60%. In RBP support, aggressive ventricular unloading was found to lead to lower cardiac efficiencies. On the other side, phasing of a PBP offers the possibility to restore cardiac efficiency and simultaneously unload the ventricle. These results may justify future studies linking optimized cardiac mechanics and efficiency to functional recovery and reverse myocardial remodeling with LVAD therapy.