Restoration of pulsatile flow reduces sympathetic nerve activity among individuals with continuous-flow left ventricular assist devices

Background-Current-generation left ventricular assist devices provide circulatory support that is minimally or entirely nonpulsatile and are associated with marked increases in muscle sympathetic nerve activity (MSNA), likely through a baroreceptor-mediated pathway. We sought to determine whether the restoration of pulsatile flow through modulations in pump speed would reduce MSNA through the arterial baroreceptor reflex. Methods and Results-Ten men and 3 women (54±14 years) with Heartmate II continuous-flow left ventricular assist devices underwent hemodynamic and sympathetic neural assessment. Beat-to-beat blood pressure, carotid ultrasonography at the level of the arterial baroreceptors, and MSNA via microneurography were continuously recorded to determine steady-state responses to step changes (200-400 revolutions per minute) in continuous-flow left ventricular assist device pump speed from a maximum of 10 480±315 revolutions per minute to a minimum of 8500±380 revolutions per minute. Reductions in pump speed led to increases in pulse pressure (high versus low speed: 17±7 versus 26±12 mm Hg; P0.01), distension of the carotid artery, and carotid arterial wall tension (P0.05 for all measures). In addition, MSNA was reduced (high versus low speed: 41±15 versus 33±16 bursts per minute; P0.01) despite a reduction in mean arterial pressure and was inversely related to pulse pressure (P=0.037). Conclusions-Among subjects with continuous-flow left ventricular assist devices, the restoration of pulsatile flow through modulations in pump speed leads to increased distortion of the arterial baroreceptors with a subsequent decline in MSNA. Additional study is needed to determine whether reduction of MSNA in this setting leads to improved outcomes.