Assessment of Microvascular Function in Angina Pectoris by Angiography-Based Index of Microcirculation Resistance: A Meta-Analysis.

Background: While the invasive index of microcirculation resistance (IMR) remains the gold standard for diagnosing coronary microvascular dysfunction (CMD), its clinical adoption is limited by procedural complexity and cost. Angiography-based IMR (Angio-IMR), a computational angiography-based method, offers a promising alternative. This study evaluates the diagnostic efficacy of Angio-IMR for CMD detection in angina pectoris (AP).

Methods: A comprehensive literature search was conducted across PubMed, Embase, Scopus, and the Cochrane Library to identify studies assessing Angio-IMR's diagnostic performance for CMD in AP populations. Primary outcomes included pooled sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the receiver operating characteristic (ROC) curve (AUC).

Results: 11 studies involving 927 patients were included. Angio-IMR demonstrated robust diagnostic performance: sensitivity 86% (95% CI: 0.83-0.90), specificity 90% (95% CI: 0.87-0.92), PPV 82% (95% CI: 0.78-0.86), NPV 91% (95% CI: 0.88-0.94), and AUC 0.91 (95% CI: 0.89-0.94), with low heterogeneity. Subgroup analyses revealed no significant differences in diagnostic accuracy between obstructive (stenosis ≥50%) and non-obstructive coronary artery disease. Hyperemic Angio-IMR measurements (adenosine-induced) showed superior sensitivity (89% vs. 86%) and specificity (94% vs. 91%) compared to resting-state assessments by AccuFFR system. Additionally, the sensitivity (88% vs. 82%), specificity (92% vs. 86%), PPV (82% vs. 78%) and NPV (91% vs. 88%) calculated based on AccuFFR were higher than that of quantitative flow ratio (QFR).

Conclusions: Angio-IMR is a reliable, non-invasive tool for CMD identification in angina patients, particularly under hyperemic conditions. Its diagnostic consistency across stenosis severity subgroups supports broad clinical applicability.