J curve in antihypertensive therapy--does it exist? A personal point of view.

Coronary flow is maintained in the face of changing perfusion pressure (approximates to diastolic blood pressure [DBP]) by the process of autoregulation. A normal coronary artery is able to dilate fivefold (coronary flow reserve of 5); by contrast, coronary flow reserve falls in the presence of left ventricular hypertrophy [LVH] and/or coronary artery disease. Thus a fall in DBP that is normally well tolerated causes a fall in coronary flow, ECG changes, and left ventricular dysfunction in the presence of LVH and coronary artery disease. Such high-risk patients exhibit a J-curve relationship between DBP and death from coronary artery disease; lowering DBP (phase 5) to below the mid 80s would be imprudent in such patients.