Prolonged heart rate recovery time after 6-minute walk test is an independent risk factor for cardiac events in heart failure: A prospective cohort study

Objectives: To determine whether the time for peak exercise heart rate to return to resting heart rate after the 6-minute walk test (6MWT) can predict cardiac events in patients with heart failure (HF) within 2 years. Design: Prospective cohort study. Setting: HF outpatient facility at a tertiary teaching hospital. Participants: Seventy-six patients with HF, New York Heart Association functional classification II and III, and left ventricular ejection fraction <50%. Main outcome measures: Patients used a heart rate monitor to measure the time for peak exercise heart rate to return to resting heart rate after the 6MWT. Data were analysed using Polar Pro-Trainer 5 software (Kempele, Finland). Patients were followed for >2 years for cardiac events (hospitalisations and death). Results: Thirty-four patients had cardiac events during the 2-year follow-up period. However, there was a significant difference in the time to return to resting heart rate between the groups with and without cardiac events {with 3.6 (SD 1.1) vs without 2.8 (SD 1.1) minutes; mean difference of 0.79 (95% confidence interval (CI) of the difference 0.28 to 1.28; P = 0.003}. No significant differences between patients with and without cardiac events were found for mean walking distance, mean heart rate recovery at 1 minute and mean heart rate recovery at 2 minutes. The receiver operating curve discriminated between patients with and without cardiac events (área under the curve 0.71, 95% CI 0.61 to 0.81; P < 0.001). Using logistic regression analysis, prolonged time to return to resting heart rate (≥3 minutes) independently increased the risk for cardiac events 6.9-fold (95% CI 2.34 to 20.12; P < 0.001). The Kaplan–Meier curve showed more cardiac events in patients with prolonged time to return to resting heart rate (P = 0.028). Conclusions: Prolonged time to return to resting heart rate (≥3 minutes) after the 6MWT was an independent predictor of cardiac events in patients with HF.