Cerebral Blood Flow Response to Posture Transition and Walking in Older Adults with Heart Failure

Abstract

Individuals with heart failure (HF) have lower cerebral blood flow (CBF) and oxygenation at rest, and lower cerebral oxygenation at peak exercise, likely due to insufficient cardiac output and poor respiratory function; however, no studies have examined the effects of low intensity activity such as are common of activities of daily living, on cerebral hemodynamics in individuals with HF. We recruited 10 individuals with HF (aged 78±4 years, 7 men, LVEF 20- 61%), and 13 healthy age-matched controls (aged 79±8 years, 4 men, LVEF 52-73%) to examine the cerebral hemodynamic response to quiet standing and walking. Participants completed 3 transitions; 1) supine to 3-minutes standing, 2) sitting to 3-minutes walking at a self-selected slow pace, 3) sitting to 3-minutes walking at a self-selected normal pace. Portable finger plethysmography measured central hemodynamics, portable capnography measured partial pressure end-tidal carbon dioxide (PETCO2), portable transcranial Doppler ultrasound measured cerebral blood flow velocity (CBFV), and near infrared spectroscopy (NIRS) measured cerebral oxygenation. Participants with HF had lower cardiac index (Qi), compared to control participants during seated and supine rest (P < 0.001), quiet standing (P < 0.001), and normal and slow pace walking (P = 0.006). Participants with HF had an attenuated Qi response during walking compared to control participants (group x speed interaction: P = 0.008), suggesting a poor cardiac response to low intensity activity. Cerebral oxygenation was lower in participants with HF during seated and supine rest (P = 0.020), quiet standing (P = 0.034), and normal and slow pace walking (P = 0.004), compared to control participants. Repeated-measures correlation analysis was used to examine the relationship between Qi and cerebral oxygenation across exercise challenges (quiet standing, as well as slow and normal pace walking). Interestingly, there was a significant negative relationship between Qi and cerebral oxygenation (rrm = -0.53, P< 0.001) in the participants with HF, whereas there was a significant positive relationship (rrm = 0.35, P = 0.003) in the control participants. This was likely the consequence of ineffective blood flow redistribution, which has been previously documented during exercise in individuals with HF; however, this finding in the present study is particularly problematic as the experimental conditions (quiet standing and walking) are extremely common during daily living. Sustained cerebral desaturation experienced repeatedly during daily function may manifest as ischemic damage in cerebral tissue with adverse clinical outcomes. In particular, cerebral desaturation during standing and low intensity activity may partially explain poor exercise tolerance and cognitive impairment previously reported in individuals with HF.