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

Abstract

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 VO₂ 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 (R²=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 VO₂ (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.