Effect of Heart Rate Reserve on Exercise Capacity in Patients Treated with a Continuous Left Ventricular Assist Device

Abstract

We hypothesized that an inadequate increase in heart rate (HR) during exercise was associated with low peak oxygen uptake (VO2 peak) seen in left ventricular assist device (LVAD) recipients and aimed to analyze the potential relation between HR and VO2 peak and use of drugs with negative chronotropic effect. Sixty-eight LVAD recipients (44 Heartmate 2 and 24 HeartWare Ventricular Assist Device) with support duration >1 month and a VO2 peak were included from two centers. Patients were 57 ± 13 years at time of VO2 peak and LVAD support duration was 483 ± 545 days. Peak oxygen uptake was 12 ± 4 ml/kg/min (40% ± 13% of predicted). Heart rate reserve (HRR = maximal HR - resting HR) was 59 ± 22 min (75% ± 15% of predicted for age, %HRR) and was significantly associated with VO2 peak (r = 0.244, p = 0.045). Predicted heart rate reserve was associated with %Predicted VO2 peak (P = 0.011). Chronotropic incompetence (CI) was observed in 44% and VO2 peak was clearly lower in patients with CI (10 ± 2.7 vs. 13 ± 4.6 ml/kg/min, p = 0.005). Beta-blockers (BB) were prescribed to 85% and adjusting for being on target BB-dose did not affect the correlation between %predicted VO2 peak and %HRR (r = 0.33, p = 0.024). In conclusion, almost half of LVAD recipients suffer from CI which is associated with lower VO2 peak. This relation did not seem to be affected by BB therapy.