Central and Peripheral Blood Flow During Exercise With a Continuous-Flow Left Ventricular Assist Device Constant Versus Increasing Pump Speed: A Pilot Study

Background-End-stage heart failure is associated with impaired cardiac output (CO) and organ blood flow. We determined whether CO and peripheral perfusion are maintained during exercise in patients with an axial-flow left ventricular assist device (LVAD) and whether an increase in LVAD pump speed with work rate would increase organ blood flow. Methods and Results-Invasively determined CO and leg blood flow and Doppler-determined cerebral perfusion were measured during 2 incremental cycle exercise tests on the same day in 8 patients provided with a HeartMate II LVAD. In random order, patients exercised both with a constant (approximate to 9775 rpm) and with an increasing pump speed (+400 rpm per exercise stage). At 60 W, the elevation in CO was more pronounced with increased pump speed (8.7 +/- 0.6 versus 8.1 +/- 1.1 L . min(-1); mean +/- SD; P=0.05), but at maximal exercise increases in CO (from 7.0 +/- 0.9 to 13.6 +/- 2.5 L . min(-1); P<0.01) and leg blood flow [0.7 (0.5 to 0.8) to 4.4 (3.9 to 4.8) L . min(-1) per leg; median (range); P<0.001] were similar with both pumping modes. Normally, middle cerebral artery mean flow velocity increases from approximate to 50 to approximate to 65 cm . s(-1) during exercise, but in LVAD patients with a constant pump speed it was low at rest (39 +/- 14 cm . s(-1)) and remained unchanged during exercise, whereas in patients with increasing pump speed, it increased by 5.2 +/- 2.8 cm . s(-1) at 60 W (P<0.01). Conclusions-With maximal exercise, the axial-flow LVAD supports near-normal increments in cardiac output and leg perfusion, but cerebral perfusion is poor. Increased pump speed augments cerebral perfusion during exercise. (Circ Heart Fail. 2011; 4: 554-560.)