HEART-RATE ADJUSTMENT OF EXERCISE-INDUCED ST-SEGMENT DEPRESSION IDENTIFIES MEN WHO BENEFIT FROM A RISK FACTOR REDUCTION PROGRAM

Background Whether subjects identified as being at increased risk of c oronary heart disease (CHD) death by heart rate adjustment of exercise -induced ST-segment depression will benefit from therapy aimed at redu cing risk factors has not been examined. Methods and Results Exercise ECGs were performed in 11880 men from the Usual Care (UC) and Special Intervention (SI) groups of the Multiple Risk Factor Intervention Tria l. 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 abnorma l ST-segment response to exercise was defined according to standard cr iteria as greater than or equal to 100 mu V of additional horizontal o r downsloping ST-segment depression and by an ST-segment/heart rate (S T/HR) index >1.60 mu V/bpm. After 7 years of follow-up, CHD mortality was significantly lower in SI than UC men with an abnormal STI?IR inde x (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%, 70/52 11, P=NS). Risk reduction in SI men with an abnormal ST/HR index was i ndependent of age and other cardiac risk factors. In contrast, there w as no significant difference in CHD death rate between the smaller gro ups of SI and UC men with an abnormal test by standard criteria (3.6%, 7/192 versus 2.7%, 5/186, P=NS). Conclusions An abnormal ST/HR index identifies men in whom therapy aimed at reducing CHD risk factors redu ces the risk of CHD death by 61%. These findings support the applicati on of heart rate adjustment of ST depression for screening of asymptom atic subjects at increased risk of CHD to identify those who will bene fit most from risk factor-reduction programs.