Development of the Left Atrial Assist Device for Patients with Heart Failure with Preserved Ejection Fraction: First In Vivo Results

Purpose The Left Atrial Assist Device (LAAD) is a novel device in development for mechanical circulatory assistance in patients who have heart failure with preserved ejection fraction (HFpEF). The device is implantable in the mitral position and delivers blood from the left atrium to the left ventricle. We report our results of the first LAAD in vivo implantation to assess the operational performance. Methods The LAAD was implanted in calves (n=4; mean weight 78.9 kg) using cardiopulmonary bypass (CPB) support through a left atrial incision. Horizontal mattress sutures were placed circumferentially around the mitral annulus and through the LAAD sewing ring (diameter 29 mm, Fig. 1a). Various pump-operating conditions, including mean pump speeds ranging from 3,600 to 6,000 rpm, were evaluated after the CPB was weaned, and the hemodynamics for each pump setting were recorded. Results The LAAD responded to all control inputs and ran as expected during the experiment. The cardiac output and mean aortic pressure increased (from 5.3 to 6.0 L/min, and from 69 to 77 mm Hg, respectively) by increasing the pump speed from 3,600 to 4,400 rpm, while the mean left atrial pressure decreased (from 15.1 to 8.3 mm Hg). These parameters stayed the same at pump speeds of 4,400 to 5,200 rpm. The left ventricular end-diastolic pressure, central venous pressure and heart rate remained stable at speeds ranging from 3,600 to 5,200 rpm. Suction events were occasionally observed at speeds over 4,400 rpm, mainly because of the small size of the left atrium. The epicardial echocardiography showed good positioning of the LAADs, with no evidence of obstruction of the left ventricular outflow tracts (Fig. 1b). Conclusion The implantation of the LAADs in calves was successful, and the pump showed intended improvement of the hemodynamics in the normal calf hearts. Additional studies are underway to evaluate the pump performance under diastolic heart failure conditions.