Heart rate recovery after orthostatic challenge and cardiopulmonary exercise testing in older individuals: prospective multicentre observational cohort study

BACKGROUND: Impaired vagal function in older individuals, quantified by the ‘gold standard’ delayed heart rate recovery after maximal exercise (HRR(exercise)), is an independent predictor of cardiorespiratory capacity and mortality (particularly when HRR ≤12 beats min(−1)). Heart rate also often declines after orthostatic challenge (HRR(orthostatic)), but the mechanism remains unclear. We tested whether HRR(orthostatic) reflects similar vagal autonomic characteristics as HRR(exercise). METHODS: Prospective multicentre cohort study of subjects scheduled for cardiopulmonary exercise testing (CPET) as part of routine care. Before undergoing CPET, heart rate was measured with participants seated for 3 min, before standing for 3 min (HRR(orthostatic)). HRR(exercise) 1 min after the end of CPET was recorded. The primary outcome was the correlation between mean heart rate change every 10 s for 1 min after peak heart rate was attained on standing and after exercise for each participant. Secondary outcomes were HRR(orthostatic) and peak VO(2) compared between individuals with HRR(exercise) <12 beats min(−1). RESULTS: A total of 87 participants (mean age: 64 yr [95%CI: 61–66]; 48 (55%) females) completed both tests. Mean heart rate change every 10 s for 1 min after peak heart rate after standing and exercise was significantly correlated (R(2)=0.81; P<0.0001). HRR(orthostatic) was unchanged in individuals with HRR(exercise) ≤12 beats min(−1) (n=27), but was lower when HRR(exercise) >12 beats min(−1) (n=60; mean difference: 3 beats min(−1) [95% confidence interval 1–5 beats min(−1)]; P<0.0001). Slower HRR(orthostatic) was associated with lower peak VO(2) (mean difference: 3.7 ml kg(-1) min(−1) [95% confidence interval 0.7–6.8 ml kg(-1) min(−1)]; P=0.039). CONCLUSION: Prognostically significant heart rate recovery after exhaustive exercise is characterised by quantitative differences in heart rate recovery after orthostatic challenge. These data suggest that orthostatic challenge is a valid, simple test indicating vagal impairment. CLINICAL TRIAL REGISTRATION: researchregistry6550.