945-622 Impaired Heart Rate Response to Graded Exercise: Prognostic Implications of Chronotropic Incompetence

Background and MethodsTo determine the associations between exercise heart rate response, mortality and coronary heart disease (CHD) risk, 1617 male participants in the Framingham Offspring Study underwent treadill exercise testing (Bruce Protocol) and were followed for 7.7 years. Heart rate response was assessed in three ways: 1) failure to achieve age-predicted tar-get heart rate, 2) absolute increase in heart rate with exercise, and 3) percent increase in heart rate to stage 2 of exercise. The two main endpoints were all-cause mortality and incident CHD in subjects without CHD at baseline.ResultsDuring follow-up there were 60 deaths and 95 incident CHD events. 1) Failure to achieve target heart rate was associated with increased mortality (Hazards ratio [HR]=2.63, 95% CI=1.57-4.39. P=0.0002) and increased CHD risk (HR=3.49, 95% CI=2.02-4.82, P=0.0001). 2) Absolute increase in heart rate with exercise was independently and inversely related to mortality risk (HR for 12 beats per minute decrease 1.22. 95% CI 1.03-1.46, P=0.02) and CHD risk (HR=1.29, 95% CI 1.12-1.49. P=0.0004) even after adjusting for age, ST segment response, baseline heart disease (for-mortality) and traditional coronary risk factors.3) Percent increase in heart rate to stage 2 of exercise was also independently and inversely predictive of mortality (HR for 25% decrease 1.30, 95% CI 1.00-l.70, P=0.05) and incident CHD risk (HR=1.31, 95% CI=1.06-1.63. P=0.013) even after adjusting for age, exercise capacity, and (for CHD risk) traditional coronary risk factors.ConclusionAn attenuated heart rate response to exercise, a manifestation of chronotropic incompetence, is predictive of increased mortality and coronary heart disease incidenc