Electrocardiographic abnormalities and coronary heart disease mortality among hypertensive men in the multiple risk factor intervention trial

The Multiple Risk Factor Intervention Trial (MRFIT) was a primary prevention trial involving 12,286 middle-aged men at high risk of future heart attack, about two-thirds of them considered hypertensive at entry. The mortality results suggested an increased risk of coronary heart disease (CHD) death, particularly sudden death, possibly associated with hypertension control, following a stepped-care protocol including diuretics, among hypertensive MRFIT special-intervention (SI) participants with abnormalities in their rest ECG. No such adverse association was evident in the usual care (UC) group. ECG data from the Dalhousie ECG program revealed that for nearly every ECG abnormality considered, the risk of CHD death for hypertensive SI men was greater than for hypertensive UC men. The exception to this was ischemic response to exercise, for which the associated relative risk for UC men was 2.96 and for SI men 1.35 (p = 0.03 for SI/UC difference). The risk of CHD death for SI men with any ECG abnormalities compared to those without ECG abnormalities was 3.30. For UC men the corresponding relative risk was 1.22 (p = 0.03 for difference in relative risk). The results suggest that the influence of the presence of ECG abnormalities on the response to hypertension intervention may be heterogenous, in that certain abnormalities (particularly repolarization abnormalities at rest, and absent or low-amplitude U waves at rest and in post-exercise ECG) may be associated with an adverse response or reduced effectiveness of hypertension intervention, whereas an ischemic ST response to exercise may be associated with a beneficial response to intensive hypertension control efforts.