Heart rate adjustment of exercise-induced ST-segment depression identifies men who benefit from a risk factor...

Whether subjects identified as being at increased risk of coronary heart disease (CHD) death by heart rate adjustment of exercise-induced ST-segment depression will benefit from therapy aimed at reducing risk factors has not been examined.

Exercise ECGs were performed in 11,880 men from the Usual Care (UC) and Special Intervention (SI) groups of the Multiple Risk Factor Intervention Trial. UC men were referred to customary sources of care in the community; SI men received counseling on smoking cessation and dietary reduction of cholesterol, and stepped-care therapy for hypertension. An abnormal ST-segment response to exercise was defined according to standard criteria as > or = 100 microV of additional horizontal or downsloping ST-segment depression and by an ST-segment/heart rate (ST/HR) index >1.60 microV/bpm. After 7 years of follow-up, CHD mortality was significantly lower in SI than UC men with an abnormal ST/HR index (2.4%, 19/786 versus 5.3%, 39/729, P=.005) but was comparable in SI and UC men with a normal ST/HR index (1.6%, 84/5154 versus 1.3%, 70/5211, P=NS). Risk reduction in SI men with an abnormal ST/HR index was independent of age and other cardiac risk factors. In contrast, there was no significant difference in CHD death rate between the smaller groups of SI and UC men with an abnormal test by standard criteria (3.6%, 7/192 versus 2.7%, 5/186, P=NS).

An abnormal ST/HR index identifies men in whom therapy aimed at reducing CHD risk factors reduces the risk of CHD death by 61%. These findings support the application of heart rate adjustment of ST depression for screening of asymptomatic subjects at increased risk of CHD to identify those who will benefit most from risk factor-reduction programs.