Heart rate recovery of individuals undergoing cardiac rehabilitation after acute coronary syndrome

International audienceBackground: An efficient cardiac rehabilitation programme (CRP) can improve the functional ability of patients after acute coronary syndrome (ACS).Objective: To examine the effect of a CRP on parasympathetic reactivation and heart rate recovery (HRR) measured after a 6-min walk test (6MWT), and correlation with 6MWT distance and well-being after ACS.Methods: Eleven normoweight patients after ACS (BMI < 25 kg/m(2); 10 males; mean [SD] age 61 [9] years) underwent an 8-week CRP. Before (pre-) and at weeks 4 (W4) and 8 (W8) during the CRP, they performed a 6MWT on a treadmill, followed by 10-min of seated passive recovery, with HRR and HR variability (HRV) recordings. HRR was measured at 1, 3, 5 and 10 min after the 6MWT (HRR1, HRR3, HRR5, HRR10), then modelized by a mono-exponential function. Time-domain (square root of the mean of the sum of the squares of differences between adjacent normal R-R intervals [RMSSD]) and frequency-domain (with high-and low-frequency band powers) were used to analyse HRV. Participants completed a mental and physical well-being questionnaire at pre-and W8. Exhaustion after tests was assessed by the Borg scale. Pearson correlation was used to assess correlations.Results: HRR3, HRR5 and HRR10 increased by 37%, 36% and 28%, respectively, between pre-and W8 (P < 0.05), and were positively correlated with change in 6MWT distance (r = 0.58, 0.66 and 0.76; P < 0.05). Percentage change in HRR3 was positively correlated with change in well-being (r = 0.70; P = 0.01). Parasympathic reactivation (RMSSD) was improved only during the first 30 sec of recovery (P = 0.04).Conclusion: Among patients undergoing a CRP after ACS, increased HRR after a 6MWT, especially at 3 min, was positively correlated with 6MWT distance and improved well-being. HRR raw data seem more sensitive than post-exercise HRV analysis for monitoring functional and autonomic improvement after ACS