BLOOD PRESSURE TARGETS FOR PATIENTS WITH CORONARY ARTERY DISEASE: IS LOWER BETTER?
Clive Rosendorff, M.D., Ph.D., Mount Sinai School of Medicine, New York, NY, USA
Successive reports of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNP) have lowered the blood pressure targets for therapy. The latest, JNC 7, recommended in 2003 a goal of
< 140/90 mm Hg, and <130/80 for patients with diabetes and chronic kidney disease. An American Heart Association Scientific Statement added to this; patients with coronary artery disease, coronary artery disease equivalents, or who are at high risk for developing coronary artery disease, should also have as a B.P. goal <130/80 mm Hg. The problem with a “lower is better” strategy is that a low diastolic B.P., if below the lower limit of coronary autoregulation, will impair myocardial perfusion.
This may result in critical myocardial ischemia, especially in conditions of high myocardial oxygen demand, such as exercise and left ventricular hypertrophy, or when there is reduced myocardial oxygen supply as in established occlusive coronary artery disease. There have been some clinical trials which have addressed this problem, and there is consensus that low B.P. targets are protective for stroke, but the data for coronary events are inconclusive.