It is theoretically possible, therefore, that although lower- ing BP improves cardiovascular outcomes in hypertensive patients (as long as coronary perfusion is maintained above the lower autoregulatory limit for coronary blood flow), any further reduction of DBP to levels below the lower autoregu- latory limit could reduce coronary blood flow. This could be translated to an upturn in the incidence of coronary events as DBP is lowered beyond this point, especially when myocar- dial oxygen consumption is increased such as during exercise. The relationship between DBP and coronary events would, if this were true, show a J-shaped curve. A major difficulty is that we do not have data on the DBP level that corresponds to the lower limit of autoregulation in the human coronary circu- lation, in healthy individuals, or in patients with hypertension and CAD. It would also be reasonable to assume that a rapid reduction in DBP to very low levels may be more hazardous in patients with combined hypertension and CAD, although we have no experimental or clinical trial evidence to support this idea. We therefore must rely on clinical studies with surrogate end points and the few relevant clinical trials with outcomes data to attempt to resolve this issue. 3.2. Clinical Studies 3.2.1. 