(A) Coronary flow reserve versus arteriographic percent diameter stenosis in canine experimental model. Adapted, with permission, from Gould et al. (1). (B) Coronary flow reserve in open-chest humans at bypass surgery versus arteriographic percent diameter stenosis. Solid or open circles or squares indicate different coronary arteries. Reproduced, with permission, from White et al. (12). RCA = right coronary artery; other abbreviations as in Figure 1.