Cerebral blood flow during exercise in heart failure: Impact 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 (LVADs). We hypothesised that subjects implanted with LVADs would exhibit impaired cerebrovascular responses to cycle exercise when compared to age- and sex-matched healthy CTRL subjects, but enhanced responses relative to subjects with HF.

METHODS: Internal carotid artery [ICA] blood flow, and intra-cranial 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 9 LVAD participants (58±15yrs; 87±16kg; 172±8 cm, 6♂), 9 age- and sex-matched subjects with HF (58±8yrs; 84±11kg;177±6cm), and 9 CTRL (55±14yrs; 74±16kg;168±10cm).

RESULTS: At rest, ICA hemodynamics (velocity, shear rate and flow) were greater in CTRLs and LVADs than HF (p<0.05). Higher MCAv (+5.52±1.59 cm.s, p=0.003) and PCAv (+5.82±1.41 cm.s, p=0.001) were also observed in LVAD subjects than healthy CTRLs. 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, CTRLs and LVADs 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 cerebral blood flows at rest and during exercise than matched HF participants, but attenuated brain blood flows during exercise when compared to healthy subjects. Cerebral blood flows should be considered when designing exercise training interventions in patients with HF and LVADs.