Electrocardiographic changes during antihypertensive therapy in the International Prospective Primary Prevention Study in Hypertension.

In the International Prospective Primary Prevention Study in Hypertension, electrocardiographic changes before and during 3- to 5-year antihypertensive treatment were investigated in a cohort of 5819 men and women aged 40 to 64 years with entry diastolic blood pressures of 100 to 125 mm Hg. They were randomly allocated to treatment regimens that either included or excluded the slow-release beta-blocker oxprenolol. Electrocardiograms (ECGs) were assessed using the Minnesota Code and assigned to groups of normal ECGs or ECGs with pressure-related, ischemic, "intermediate," or "other" abnormalities. Antihypertensive treatment was associated with a decrease (mainly in men) of pressure-related and (mainly in women) of intermediate abnormalities. Ischemic abnormalities increased, particularly in men. Inclusion of the beta-blocker resulted in a greater reduction in intermediate abnormalities and in a lesser increase in ischemic abnormalities. Better blood pressure control was associated with a lesser increase in ischemic abnormalities and in a regression of pressure-related abnormalities. The presence of ST segment depression and of a complete left bundle branch block in the entry ECG was associated with a significant risk for sudden death and myocardial infarction. Optimal blood pressure control prevents pressure-induced cardiac target organ damage and, hence, heart failure, and may delay the progression of ischemic abnormalities. This tallies with the lower critical cardiac event rate associated with lower blood pressure that was observed in the same study.