Pump speed modulations and sub-maximal exercise tolerance in left ventricular assist device recipients: A double-blind, randomized trial

Background The effect of pump speed increase on sub-maximal exercise tolerance, corresponding to activities of daily living (ADLs), is unknown. The aim of this study was to determine the effects of increasing pump speed during exercise at a sub-maximal level below anaerobic threshold (AT). Methods Patients each completed 3 exercise sessions on an ergometer cycle. On Day 1 workload at AT was defined. On Day 2 of the study, 2 sub-maximal tests at a workload below AT were undertaken: one at fixed baseline pump speed (Speed^base) and the other with baseline pump speed + 800 rpm (Speed^inc). The sequence of the 2 sub-maximal tests was determined by randomization. Both patient and physician were blinded to the sequence. Exercise duration, oxygen consumption (VO2) and rate of perceived exertion (RPE), using the Borg scale (score 6 to 20), were recorded. Results Nineteen patients (all with a HeartMate II ventricular assist device) completed 57 exercise tests. Baseline pump speed was 9,326 ± 378 rpm. At AT, workload was 63 ± 26 W (25 to 115 W) and VO₂ was 79 ± 14% of maximum. Exercise duration improved by 106 ± 217 seconds (~13%) in Speed^inc compared with Speed^base (837 ± 358 vs 942 ± 359 seconds; p = 0.048). The RPE was 13.2 ± 2.5 in Speed^base vs 12.7 ± 2.4 in Speed^inc (p = 0.2). Conclusion Increasing pump speed by 800 rpm during sustained, low-intensity physical activity is safe and prolongs exercise duration in patients supported with a HeartMate II device. Automated pump speed increase during light exercise may contribute to improved quality of life by facilitating ADLs.