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.

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. Prospective cohort study. HF outpatient facility at a tertiary teaching hospital. Seventy-six patients with HF, New York Heart Association functional classification II and III, and left ventricular ejection fraction <50%. 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). 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 1minute and mean heart rate recovery at 2minutes. 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 (≥3minutes) 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). Prolonged time to return to resting heart rate (≥3minutes) after the 6MWT was an independent predictor of cardiac events in patients with HF.

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