Central and peripheral blood flow during exercise with a continuous-flow left ventricular assist device: constant...

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.

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 (≈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 ≈50 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).

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.