Continuously maintaining positive flow avoids endocardial suction of a rotary blood pump with left ventricular bypass

This study showed the usefulness of maintaining positive pump flow to avoid endocardial suction and as an assist bypass. Three calves were implanted w ith centrifugal pumps. Hemodynamics and pump parameters were measured at va rying pump speeds (from 1,100 to 2300 rpm). In each test pump, speed was ad justed to create 3 hemodynamic states: both positive and negative flow (PNF ), positive and zero now (PZF), and continuously positive now (CPF). The pu mp flow volume was determined during systole (Vs) and diastole (Vd). Vs in PNF was 29.6 ml and was not significantly different from Vs in PZF (p > 0.1 5). Vd in PNF was significantly different from Vd in PZF (p < 0.05). All by pass rates of PNF were over 30% of pulmonary flow. All PZF bypass rates wer e between the PNF rate and the CPF rate. These data showed that PZF satisfi ed the mini mum requirement of assist flow and was under 100% bypass. Thus, PZF may avoid endocardial suction.