Abstract
Rotary left ventricular assist devices (LVADs) show weaker response to preload and greater response to afterload than the native heart. This may lead to ventricular suction or pulmonary congestion, which can be deleterious to the patient's recovery. A physiological control system which optimizes responsiveness of LVADs may reduce adverse events. This study compared eight physiological control systems for LVAD support against constant speed mode. Pulmonary (PVR) and systemic (SVR) vascular resistance changes, a passive postural change and exercise were simulated in a mock circulation loop to evaluate the controller's ability to prevent suction and congestion and to increase exercise capacity. Three active and one passive control systems prevented ventricular suction at high PVR (500 dynescm(-5)) and low SVR (600 dynescm(-5)) by decreasing LVAD speed (by 200-515rpm) and by increasing LVAD inflow cannula resistance (up to 1000 dynescm(-5)) respectively. These controllers increased LVAD preload sensitivity (to 0.196-2.415 Lmin(-1)mmHg(-1)) compared to the other control systems and constant speed mode (0.039-0.069Lmin(-1)mmHg(-1)). The same three active controllers increased pump speed (600-800rpm) and thus LVAD flow by 4.5Lmin(-1) during exercise which increased exercise capacity. Physiological control systems that prevent adverse events and/or increase exercise capacity may help improve LVAD patient conditions.
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