Hypertension and coronary artery disease: cause and effect

NATURE OF RELATIONSHIP BETWEEN HYPERTENSION AND CORONARY ARTERY DISEASE: Epidemiological data indicate a strong and consistent link between hypertension and coronary artery disease. This does not mean that hypertension is the cause of coronary artery disease. Less than a quarter of the risk of developing coronary artery disease can be attributed to raised blood pressure. Furthermore, in individuals, hypertension is only weakly predictive and hence blood pressure cannot be relied upon to identify those with a particularly high risk. EFFECT OF A REDUCTION IN BLOOD PRESSURE ON CORONARY ARTERY DISEASE: The results of outcome trials, largely in men with mild to moderate uncomplicated hypertension, demonstrate that a modest short-term reduction in blood pressure confers a reduction in coronary artery disease events of about 16%, against the expectation from observational studies of about 22.5%. Explanations for the apparent shortfall include the putative theory that metabolic effects of the drugs used in the trials (mainly thiazides and beta-blockers) offset the beneficial effect of the blood pressure reduction. However, from consideration of epidemiological findings, it is clear that a large proportion (over 75%) of events in hypertensive patients is unlikely to be preventable by managing the elevated blood pressure alone. TREATMENT CONSIDERATIONS: Since arterial pressure interacts in a more than additive manner with coincident coronary risk factors, treatment should be initiated on the basis of overall risk and directed by predictors of myocardial infarction. In addition to a sustained level of blood pressure, these predictors include established coronary artery disease, older age and cigarette smoking. BEYOND BLOOD PRESSURE REDUCTION: Whether metabolically neutral antihypertensive drugs can reduce the shortfall between expected and observed benefit remains uncertain. However, some newer agents (angiotensin converting enzyme inhibitors and calcium antagonists) appear to have an effect on vascular structure and function that is independent of blood pressure reduction. If these advantages are confirmed in clinical trials, these drugs offer the prospect of a much greater impact on coronary artery disease than currently obtained.