Angiography-based coronary microvascular assessment with and without intracoronary pressure measurements: a systematic review

Abstract Background In recent years, several indices have been proposed for quantifying coronary microvascular resistance. We intended to conduct a comprehensive review that systematically evaluates indices of microvascular resistance derived from angiography. Objective The objective of this study was to identify and analyze angiography-derived indices of microvascular resistance that have been validated against an invasive reference method. We aimed to compare their limits of agreement with their reference methods and explore their advantages and inherent limitations. Methods and results We searched PubMed from inception until 2022 for studies on different techniques for quantifying microvascular resistance. Seven studies met the inclusion criteria. Five studies included techniques that applied calculations based solely on invasive angiography, and were validated against invasively measured thermodilution-derived index of microvascular resistance. The remaining two studies combined angiography with invasively measured intracoronary pressure data, and were validated against invasive Doppler measurements. We converted the ± 1.96 standard deviation limits of agreement with the reference method from the seven studies into percentages relative to the cut-off value of the reference method. The lower limits of agreement for angiography-based methods ranged from − 122 to − 60%, while the upper limits ranged from 74 to 135%. The range of the limits of agreement was considerably lower for the two combined angiography- and pressure-based methods, standing at − 52 to 60% and − 25 to 27%. Conclusion Our findings suggest that combined angiography- and pressure-based methods provide a more reliable assessment of microvascular resistance compared to methods relying solely on angiography. Graphical Abstract Central illustration. Comparative assessment of image-based methods quantifying microvascular resistance with and without intracoronary pressure measurements. Angiography-based methods rely on angiography alone to calculate the microvascular resistance by utilizing angiographic frame counting to extrapolate coronary flow (Q) and subsequently deriving distal coronary pressure using fluid dynamic equations. Combined angiography- and pressure-based methods utilize invasive intracoronary pressure gradients measured during rest and maximal vasodilation to determine coronary flow in their calculation of microvascular resistance. The combined methods showed more acceptable levels of agreement with their reference methods compared to angiography-based methods alone.