CARD22: Hemolysis Using Left Atrial Assist Device with Constant Flow: Preliminary Testing of Initial Design

Abstract

Purpose: The Left Atrial Assist Device (LAAD) (Figure 1A&B) is a mechanical circulatory support device proposed to treat patients in heart failure with preserved ejection fraction (HFpEF). Patients with HFpEF often have a thickened left ventricle (LV) with altered compliance and stiffness that reduces volume capacity. This mixed flow pump is implanted in the mitral valve position and will help move blood from the left atrium into the stiffened LV. The functioning LV will pump blood to the rest of the body keeping physiologic blood flow paths intact. The purpose of this study was to evaluate initial hemocompatibility by in vitro hemolysis tests on a preliminary pump design at several conditions. Method: Hemolysis tests (n=3) were performed in a temperature-controlled loop (Figure 1C) with whole bovine blood from two sources on two different days. The set up used one bag as the reservoir with pump flow (PF) measured after the screw clamp, and pressures monitored at the pump inlet (Pin) and outlet (Pout). The pump speed was set to 4,000 RPM (n=2) and 4,400 RPM (n=1) corresponding to PF between 3.5 - 6.3 L/min and delta pressure (Pout-Pin) between 75 - 101 mm Hg. Hematocrit and plasma free hemoglobin measurements at timed intervals were collected to determine the normalized index of hemolysis (NIH). Results: The average NIH of the three LAAD tests was 0.02 ± 0.01 g/100L (Figure 1D). The average flow for each test was maintained (± 0.1 L/min). In our previous studies with bovine blood, the BP80X (Medtronic, Minneapolis) performed with an average NIH of 0.03 ± 0.02 g/100L. The LAAD performed within an acceptable limit of hemolysis in all three test conditions.