Heart rate recovery immediately after treadmill exercise and left ventricular systolic dysfunction as predictors of mortality: the case of stress echocardiography.

BACKGROUND An attenuated heart rate recovery after exercise has been shown to be predictive of mortality. In prior studies, recovery heart rates were measured while patients were exercising lightly, that is, during a cool-down period. It is not known whether heart rate recovery predicts mortality when measured in the absence of a cool-down period or after accounting for left ventricular systolic function. METHODS AND RESULTS We followed 5438 consecutive patients without a history of heart failure or valvular disease referred for exercise echocardiography for 3 years. Heart rate recovery was defined as the difference in heart rate between peak exercise and 1 minute later; a value </=18 beats per minute was considered abnormal. Patients assumed the left lateral decubitus position after exercise. An abnormal heart rate recovery was present in 805 patients (15%); during follow-up, 190 died. An abnormal heart rate recovery was predictive of death (9% versus 2%, hazard ratio [HR] 3.9, 95% CI 2.9 to 5.3, P<0.0001) and predicted death whether or not left ventricular systolic dysfunction (ejection fraction </=40%) was present. After adjusting for age, sex, exercise capacity, left ventricular systolic function, presence or absence of myocardial ischemia, and other confounders, an abnormal heart rate recovery remained predictive of death (adjusted HR 2.09, 95% CI 1.49 to 2.82, P<0.001). CONCLUSIONS Even in the absence of a cool-down period and even after accounting for left ventricular systolic function, heart rate recovery is a powerful and independent predictor of death.