Heart Rate Recovery after Submaximal Exercise Test and 20 Year All-Cause Mortality Test in Asymptomatic Russian and American Men: The Lipid Research Clinics Study
Background. Heart Rate Recovery at two minutes post exercise (HRR2) was reported to be a predictor of death in the US-Lipid Research Clinics (LRC) Study. Objective. To extend study of HRR2 to the USSR-LRC population, with higher mortality rates and cardiovascular (CVD) risk factor levels. Design and methods. Among the LRC cohorts, using a standardized protocol, HRR2 after a treadmill submaximal test and CVD risk factors was measured in 1294 Russian and 1589 American men ages 39-60 years, free of coronary disease at baseline, not taking cardio-active drugs, followed for an average of 17.5 years for all cause mortality. Kaplan-Meier curves and stratified Cox proportional hazard models were employed for analysis. Results.There were 391 (30.2%) deaths in the Russian and 232 (14.6%) in the American men, and mean HRR2 was 59.6 bpm (95% CI 58.3-60.3) and 53.2 (CI 52.6-53.8) respectively. All cause mortality increased monotonically with decreasing HRR2 and was predicted by HRR2 adjusting for age, physical fitness, ST-T response, cholesterol and blood pressure, and alcohol intake in both samples. For each 15 bpm (1 SD) decrease in HRR2 the crude hazard rate ratio was 1.61 (95% CI 1.37, 1.89) in Russian and 1.37 (1.23, 1.51) in American men among smokers; upon adjustment the values were 1.34 (95% CI 1.16-1.56) and 1.39 (1.13-1.70) respectively. Conclusion. Delay in the recovery of heart rate after a submaximal exercise test was associated with all cause mortality, statistically independent of cardiovascular risk factors in both Russian and American men.The extension of these associations to a higher risk population, suggests the potential utility of HRR2 for CVD risk assessment.