Workload at the heart rate of 100 beats/min and mortality in middle-aged men with known or suspected coronary heart disease.

Abstract

OBJECTIVE: To investigate whether a workload which an individual is able to perform at the heart rate (HR) of 100 beats/min (WL(100)) independently predicts mortality in middle-aged men with known or suspected coronary heart disease (CHD). DESIGN: Prospective population-based study based on 365 middle-aged men with known or suspected CHD at baseline. RESULTS: During an average follow-up of 11.1 years, there were 75 deaths (20.5%). In Cox multivariable models mortality increased by 72% (95% CI 32% to 122%, p<0.001) with 1 SD (34 Watts) decrement in WL(100) after adjustment for age, examination year, alcohol consumption, body mass index, cigarette smoking, cardiac insufficiency, history of myocardial infarction, diabetes, myocardial ischaemia during exercise test, serum low-density lipoprotein and high-density lipoprotein cholesterol, systolic and diastolic blood pressure at rest, testing protocol, and use of HR-lowering medication. The risk of death was 2.4 (95% CI 1.5 to 4.0, p<0.001) times higher in 130 men with WL(100) <55 W than in 235 men with WL(100) >or=55 W. In men using and not using HR-lowering medication the risk of death increased 72% (95% CI 14% to 163%, p = 0.01), and 54% (95% CI 14% to 108%, p = 0.005) with 1 SD decrement in WL(100), respectively. WL(100 )improved the predictive power of the adjusted Cox models including other HR and exercise test variables. CONCLUSIONS: WL(100) predicts mortality in men with known or suspected CHD. The association of WL(100) with mortality was not explained by other well-established HR and exercise test variables. WL(100) is derived from a submaximal test which avoids the cardiovascular risks associated with a high-intensity exertion.