Angiography-derived index of microcirculatory resistance in older patients with acute coronary syndrome undergoing percutaneous coronary intervention

Background Coronary microvascular dysfunction (CMD) plays a significant role in the prognosis of patients with ischaemic heart disease. Aims In this analysis of the study to Improve Clinical Outcomes in high-risk patieNts with acute coronary syndrome (ICON1), we investigated the association between CMD and long-term outcomes in older patients with non-ST-elevation acute coronary syndrome (NSTE-ACS) undergoing percutaneous coronary intervention (PCI). Methods Patients aged ≥75 years with NSTE-ACS undergoing PCI were included. Post-PCI angiography-derived index of microcirculatory resistance (IMR angio ) was assessed. The primary endpoint was a composite of all-cause death, myocardial infarction, any revascularisation, any hospital readmission, or heart failure events. Results A total of 152 patients with post-PCI IMR angio assessment were included. The receiver-operating characteristics (ROC)-defined cut-off for predicting the primary endpoint was 40 U. High post-PCI IMR angio (≥40 U) was observed in 38 patients and was independently associated with the primary endpoint at both 1- and 5-year follow-up (hazard ratio [HR] 4.82, 95% confidence interval [CI] 2.02–11.51, p < 0.01 and HR 4.18, 95% CI 2.20–7.95, p < 0.01; respectively). A multivariate model was developed to predict the primary endpoint at 1 and 5 years. The inclusion of high post-PCI IMR angio significantly improved its discriminatory ability for the primary endpoint at 1 year (area under the curve [AUC] 0.74 vs. 0.85, p = 0.04) and 5 years (AUC 0.74 vs. 0.84, p = 0.03). Conclusion Older NSTE-ACS patients with high post-PCI IMR angio have worse long-term clinical outcomes. In this clinical setting, post-PCI IMR angio , together with conventional risk factors and angiographic variables, may help identifying a higher-risk phenotype. Study registration: NCT01933581, https://clinicaltrials.gov/study/NCT01933581