Cerebral Blood Flow during Exercise in Heart Failure: Effect of Ventricular Assist Devices

Introduction In healthy individuals, cerebral blood flow (CBF) increases during exercise, but few studies have compared changes in CBF during exercise in patients with heart failure (HF) to healthy controls (CTRL) or assessed the effects of left ventricular assist devices (LVAD). We hypothesized that subjects implanted with LVAD would exhibit impaired cerebrovascular responses to cycle exercise when compared with age- and sex-matched healthy CTRL subjects but would have enhanced responses relative to subjects with HF. Methods Internal carotid artery (ICA) blood flow and intracranial middle (MCAv) and posterior cerebral (PCAv) artery velocities were measured continuously using Doppler ultrasound, alongside cardiorespiratory measures at rest and in response to an incremental submaximal cycle ergometer exercise protocol in nine LVAD participants (58 ± 15 yr, 87 ± 16 kg, 172 ± 8 cm, six females), nine age- and sex-matched subjects with HF (58 ± 8 yr, 84 ± 11 kg, 177 ± 6 cm), and nine CTRL (55 ± 14 yr, 74 ± 16 kg, 168 ± 10 cm). Results At rest, ICA hemodynamics (velocity, shear rate, and flow) were greater in CTRL and LVAD than that in HF (P < 0.05). Higher MCAv (+5.52 ± 1.59 cm·s^-1, P = 0.003) and PCAv (+5.82 ± 1.41 cm·s^-1, P = 0.001) were also observed in LVAD subjects than healthy CTRL. During exercise, ICA flow increased at all workloads in CTRL, but not in HF or LVAD groups. MCAv increased from baseline in both HF and CTRL participants (P = 0.0001), but not in LVAD subjects. Nonetheless, CTRL and LVAD showed higher MCAv (P = 0.006) and PCAv (P < 0.0001) values throughout exercise than HF. Conclusion Our findings indicate that LVAD subjects exhibit higher CBF at rest and during exercise than matched HF participants but attenuated brain blood flows during exercise when compared with healthy subjects. CBF should be considered when designing exercise training interventions in patients with HF and LVAD.