Diagnostic Accuracy of Quantitative Coronary Analysis as Compared with Instantaneous Wave-Free Ratio in Intermediate Coronary Lesions: A Prospective Vessel-Level Study.

Background: Instantaneous wave-free ratio (IFR) represents a new vasodilator-free innovative approach which is considered as a gold standard for functional assessment of the hemodynamic significance of intermediate coronary stenoses. Although relatively safe, iFR is still an invasive procedure that has its potential hazards, complications and cost. Two-dimensional quantitative coronary analysis (2D-QCA) is a non-invasive technique that has emerged robustly as an excellent and attractive tool for delineating coronary anatomy. Aims: To assess the ability of two-dimensional quantitative coronary analysis (2D-QCA) to guide decision-making for quantification of severity of intermediate coronary stenoses (40-80% diameter stenosis) in each of the three main coronary vessels, by evaluating its accuracy in predicting true instantaneous wave-free ratio (iFR) results. Methods and results: 2D-QCA followed by iFR were performed for intermediate coronary lesions (40-80% diameter stenosis by visual assessment) discovered during coronary angiography. 2D-QCA was used to measure MLA, MLD and lesion length. This was followed by iFR measurement for the same lesion. 2D-QCA was then compared to the iFR measurements in order to assess its accuracy in prediction of true iFR result. A total of 277 intermediate lesions (155 LAD, 67 LCX, 55 RCA) in 209 vessels from 166 patients were analyzed. Males comprised ~68% of cases; mean ages were 53.3 ± 8.2 (LAD), 55.7 ± 8.9 (LCX), and 56.0 ± 8.8 years (RCA). Disagreement between modalities occurred mostly in LAD (24.5%), followed by RCA (21.8%) and LCX (14.9%). Per-vessel QCA accuracy (AUC) for predicting iFR was highest in LCX (78.5%), then RCA (72.2%), and lowest in LAD (66.6%) (all p < 0.005). Optimal QCA stenosis area cutoffs were 50.5% (LCX), 52.5% (RCA), and 53.5% (LAD), with sensitivities of 72.0%, 62.1%, and 63.2%, and specificities of 69.0%, 65.4%, and 65.8%, respectively. Conclusion: 2D-QCA can be a practical tool that bears the potential of improving angiography-based assessment of intermediate lesions regarding its prediction for functional significance without any additional costs, especially when invasive functional assessment methods are not available or contraindicated. Although, this would minimize the burden and the time of invasive procedure, 2D-QCA cannot totally replace invasive functional assessment (iFR, FFR) of intermediate coronary stenoses especially in LAD intermediate lesions.