Long-Term Prognostic Impact of Changes in Coronary Angiography–Derived Index of Microcirculatory Resistance Following PCI

BACKGROUND: Angiography-derived index of microcirculatory resistance (angio-IMR) is a reliable measure for assessing coronary microvascular function. However, the prognostic significance of changes in angio-IMR (Δangio-IMR) remains unclear. OBJECTIVES: The aim of this study was to assess the long-term prognostic utility of Δangio-IMR following percutaneous coronary intervention (PCI) in patients with intermediate coronary stenosis. METHODS: A total of 814 vessels with intermediate coronary stenosis that underwent PCI were enrolled from the FLAVOUR (Fractional Flow Reserve and Intravascular Ultrasound for Clinical Outcomes in Patients with Intermediate Stenosis) trial. The primary endpoint was target vessel failure (TVF) during long-term follow-up, defined as a composite of cardiac death, target vessel-related myocardial reinfarction, and target vessel revascularization. RESULTS: The median Δangio-IMR was 2.02 (Q1-Q3: 0.50-5.00). Using the 75th percentile (Δangio-IMR >5) as the cutoff, 203 vessels were assigned to the high Δangio-IMR group. Vessels with high Δangio-IMR demonstrated a significantly elevated risk for TVF compared with those with low Δangio-IMR (15.62% vs 9.47%; HR: 1.82; 95% CI: 1.15-2.88; P = 0.011). High Δangio-IMR independently predicted TVF (HR: 1.72; 95% CI: 1.04-2.83; P = 0.034). There was a notable interaction effect between Δangio-IMR and post-PCI angio-IMR (P = 0.028). A stratified analysis by post-PCI angio-IMR revealed that vessels with high Δangio-IMR showed a markedly increased TVF risk compared with vessels with low Δangio-IMR in those with post-PCI angio-IMR >25 (26.2% vs 11.9%; HR: 5.18; 95% CI: 1.28-20.94; P = 0.021), whereas no such association was observed in those with post-PCI angio-IMR ≤25 (12.6% vs 9.3%; HR: 1.33; 95% CI: 0.77-2.29; P = 0.305). CONCLUSIONS: An elevated Δangio-IMR correlates with a heightened risk of TVF in vessels with intermediate coronary stenosis underwent PCI. ΔAngio-IMR could be used as a valuable risk stratification indicator, particularly in patients with high post-PCI angio-IMR.