Validation of a new quantitative coronary angiography analysis system used to evaluate densitometric lumen remodelling

Abstract

Arterial lumen volume, determined by sequential coronary angiography, could have advantages over more commonly used variables (such as percent stenosis or minimal lumen diameter) as a primary endpoint in clinical trials evaluating post-angioplasty restenosis or atherosclerotic plaque progression. We validated a quantitative coronary angiography analysis (QCA) system aimed at measuring lumen volume from coronary angiography films by a densitometric method. Using images of polyacrylate models filled with different concentrations of contrast medium, accuracy (mean of the differences between known and measured values of a measurement) and precision (standard deviation of the difference) were lower than or equal to 0.09 and 0.21 mm, respectively, for diameters ranging from 1.5 to 16 mm. In terms of volume measurement, accuracy was 30.2 mm³ and precision 5.7 mm³ for a known volume of 620.2 mm³. To assess the short-term variations of lumen volume measurements under conditions resembling those encountered in clinical trials, a special image comparison program of the QCA system was used to measure the same coronary artery segment on two images taken 10 minutes apart in 21 patients. The mean difference between the two measurements was 1.7 ± 12.4 mm³, with a coefficient of variation of 15%. An error of ± 2 frames in the selection of images to be analyzed had little influence on the results. We conclude that the QCA system provides easy-to-achieve standardization of the image acquisition process and sufficient reproducibility for repeated measurement of volume of a coronary artery segment, which can serve as the primary endpoint in clinical trials evaluating atherosclerotic plaque progression or restenosis after angioplasty.