Relationship between changes in heart rate recovery after cardiac rehabilitation on cardiovascular mortality in patients with myocardial infarction

BackgroundHeart rate recovery (HRR) at predischarge exercise stress test predicts all-cause mortality in patients with myocardial infarction (MI), but the relationship between improvement in HRR with exercise training and clinical outcomes remains unclear.ObjectiveThe purpose of this study was to evaluate the effect of change in HRR after exercise training on clinical outcomes in MI patients.MethodsThe study included 386 consecutive patients with recent MI who were enrolled into our cardiac rehabilitation program. All patients underwent symptom-limited treadmill testing at baseline and after exercise training, and were prospectively followed-up in the outpatient clinic.ResultsTreadmill testing revealed significant improvement in HRR after 8 weeks of exercise training (17.5 ± 10.0 bpm to 19.0 ± 12.3 bpm, P = .011). After follow-up of 79 ± 41 months, 40 (10.4%) patients died of cardiac events. Multivariate Cox regression analysis revealed that diabetes (hazard ratio [HR] 2.28, 95% confidence interval [CI] 1.01–5.19, P = .049), statin use (HR 0.36, 95% CI 0.16–0.80, P = .012), baseline resting heart rate ≥65 bpm (HR 5.37, 95% CI 1.33–21.61, P = .018), post-training HRR <12 bpm (HR 2.49, 95% CI 1.10–5.63, P = .028), left ventricular ejection fraction ≤30% (HR 4.70, 95% CI 1.34–16.46, P = .016), and exercise capacity ≤4 metabolic equivalents (HR 3.63, 95% CI 1.17–11.28, P = .026) were independent predictors of cardiac death. Patients who failed to improve HRR from <12 bpm to ≥12 bpm after exercise training had significantly higher mortality (HR 6.2, 95% CI 1.3–29.2, P = .022).ConclusionExercise training improved HRR in patients with recent MI, and patients with HRR increased to ≥12 bpm had better cardiac survival.