Goals of antihypertensive therapy. Is there a point beyond which pressure reduction is dangerous?

It has been widely assumed that the preventive effect of antihypertensive treatment on cardiovascular events is increased as lower blood pressure (BP) is achieved. This assumption seemed logical in light of the well-known relationship between BP level and future cardiovascular events. Hypertension, however, develops over many years and is associated with both hypertrophic and atherosclerotic changes within the coronary and peripheral vessels. Antihypertensive drugs when instituted will bring down BP and often arterial blood flow within weeks. Coronary blood flow is limited to diastole. Theoretically then, very low diastolic BPs in coronary arteries with hypertrophic and/or atherosclerotic changes might precipitate a chain of events leading to a myocardial infarction and/or a lethal arrhythmia. Recently, results from several trials have been presented indicating a J-shaped relationship between achieved BP level and incidence of coronary heart disease. These trials are reviewed and problems in the interpretation of the findings such as biaz from varying risk at entry, varying follow-up time, and choice of statistical method, are discussed. Although, the burden of evidence strongly supports the hypothesis that low attained BPs are associated with an increased risk of a coronary heart disease event, problems in the interpretation of this evidence call for further analyses of the relationship within the large hypertension trials. Until such results are at hand caution should be to avoid decreasing BP below 85 mm Hg diastolic.