Coronary artery revascularization. Critical need for, and consequences of, objective angiographic assessment of lesion severity.

T he treatment of coronary artery disease patients with revascularization procedures has escalated dramatically in the 1980s. In 1989, an estimated 450,000 coronary artery revascularization procedures were performed with either percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass graft surgery (CABG); in 1980, less than 250,000 such procedures were performed. Despite the dramatic increase in the use of coronary revascularization procedures, the relative efficacy of PTCA and CABG in the treatment of coronary artery disease patients remains poorly understood. In the last 3 years, a number of comparative randomized prospective trials evaluating the relative efficacy of PTCA and CABG have been planned and initiated. In the United States, the National Heart, Lung, and Blood Institute (NHLBI) is sponsoring two such comparative trials: the Emory Angioplasty Surgery Trial (EAST) and the Bypass Angioplasty Revascularization Investigation (BARI). Three similar trials are underway in Western Europe. Because coronary revascularization is based on the angiographic assessment of coronary lesion severity, investigators in trials comparing PTCA and CABG have had to implement objective and reproducible methodologies for assessing coronary artery lesion severity. If one is to assess the ischemia-producing potential of a particular coronary lesion, direct measurement of impairment of coronary flow and reduction in coronary flow reserve is the reference standard against which angiographic measurements must be compared.' To a variable extent, the percent coronary diameter stenosis,' minimum residual lumen diameter,2 minimum lesion cross-sectional area,3 and the flow resistance (computed from the full-lesion geometric profile)4 all correlate with measures of resting flow and coronary flow reserve. Historically, clinical assessment of coronary artery lesion severity has relied on visual determination of the percent diameter stenosis. This measurement intuitively re-