Delineating coronary epicardial stenosis status from microvascular dysfunction using pressure-drop coefficient from multicenter ILIAS registry

Introduction: Pressure-based fractional flow reserve (FFR) and flow-based coronary flow reserve (CFR) assess the functional status of coronary artery disease (CAD) during cardiac catheterization. Complex hemodynamics may not be adequately explained by either pressure or flow alone. Consequently, pressure-drop coefficient (CDP, the ratio between pressure-drop across a stenosis and distal dynamic pressure) that combines both pressure and flow measurements has been developed to distinguish between epicardial stenosis (ES) and microvascular disease (MVD). Methods: A global multicenter ILIAS registry was used to analyze CDP in relation to FFR/CFR among 961 subjects for 1342 intracoronary pressure and flow measurements. The correlation between FFR and CFR with CDP was analyzed. The receiver operating characteristic (ROC) curve was used to determine the CDP cut-off value, corresponding to FFR = 0.80 and 0.75 and CFR = 2.0. Results: Both linear (r = 0.68) and logarithmic (r = 0.75) correlation of CDP with combined FFR and CFR improved (p < 0.001) in relation to either FFR or CFR individually. The CDP cut-off values to predict the four possible disease combinations based on FFR(0.8) and CFR(2.0) are: 1) 0 to 15.78 (absence of both diseases); 2) 15.78 to 27.25 (absence of ES and presence of MVD); 3) 27.25 to 73.77 (presence of ES and absence of MVD); and 4) CDP ≥ 73.77 (presence of both diseases). Similar CDP cut-off ranges were obtained for FFR = 0.75 and CFR = 2.0. Conclusion: The established diagnostic cut-off values of CDP can differentiate between the concomitant ES and MVD, improving the functional assessment of CAD. Condensed abstract: Fractional flow reserve and coronary flow reserve assess the functional status of coronary artery disease (CAD) during cardiac catheterization, but the complex hemodynamics may not be adequately explained by either parameter alone. Pressure-drop coefficient (CDP) is a novel composite parameter that combines both pressure and flow measurements to delineate between epicardial stenosis (ES) and microvascular disease (MVD). ILIAS registry was used to analyze the diagnostic performance of CDP relative to FFR/CFR. The receiver operating characteristic curve was used to determine the CDP cut-off values, that delineate the various combinations of ES and MVD; hence, improving the functional assessment of CAD.