COMPARATIVE VALIDATION OF QUANTITATIVE CORONARY ANGIOGRAPHY SYSTEMS -RESULTS AND IMPLICATIONS FROM A MULTICENTER STUDY USING A STANDARDIZED APPROACH

Background Computerized quantitative coronary angiography (QCA) has fu ndamentally altered our approach to the assessment of coronary interve ntional techniques and strategies aimed at the prevention of recurrenc e and progression of stenosis. It is essential, therefore, that the pe rformance of QCA systems, upon which much of our scientific understand ing has become integrally dependent, is evaluated in an objective and uniform manner. Methods and Results We validated 10 QCA systems at cor e laboratories in North America and Europe. Cine films were made of ph antom stenoses of known diameter (0.5 to 1.9 mm) under four experiment al conditions: in vivo (coronary arteries of pigs) calibrated at the i socenter or by use of the catheter as a scaling device and in vitro wi th 50% contrast and 100% contrast. The cine films were analyzed by eac h automated QCA system without observer interaction. Accuracy and prec ision were taken as the mean and SD of the signed differences between the phantom stenoses, and the measured minimal luminal diameters and t he correlation coefficient (r), the SEE, the y intercept, and the slop e were derived by their linear regression. Performance of the 10 QCA s ystems ranged widely: accuracy, +0.07 to +0.31 mm; precision, +/-0.14 to +/-0.24 mm; correlation (r), .96 to .89; SEE, +/-0.11 to +/-0.16 mm ; intercept, +0.08 to +0.31 mm; and slope, 0.86 to 0.64. Conclusions T here is a marked variability in performance between systems when asses sed over the range of 0.5 to 1.9 mm. The range of accuracy, intercept, and slope values of this report indicates that absolute measurements of luminal diameter from different multicenter angiographic trials may not be directly comparable and additionally suggests that such absolu te measurements may not be directly applicable to clinical practice us ing an on-line QCA system with a different edge detection algorithm. P ower calculations and study design of angiographic trials should be ad justed for the precision of the QCA system used to avoid the risk of f ailing to detect small differences in patient populations. This study may guide the fine-tuning of algorithms incorporated within each syste m and facilitate the maintenance of high standards of QCA for scientif ic studies.