Microvascular dysfunction of the non-culprit circulation predicts poor prognosis in patients with ST-segment elevation myocardial infarction.

Background: Endothelial and microvascular dysfunction are frequently found in the non-culprit territory in patients with acute myocardial infarction (AMI). We aimed to determine whether an impaired coronary physiology of the non-culprit territory impacts long-term prognosis. Methods: FISIOIAM was an observational single-center study which included patients with AMI and another coronary artery lesion in a different territory. Intracoronary physiology of the non-culprit artery was analyzed early after primary percutaneous coronary intervention of the culprit artery, using fractional flow reserve (FFR), index of microcirculatory resistance (IMR), coronary flow reserve (CFR), endothelium-dependent CFR (eCFR) and macrovascular endothelial function . Patients were followed for a composite outcome of cardiovascular death, non-fatal myocardial infarction, coronary revascularization, and hospitalization due to heart failure or unstable angina. Results: A total of 84 patients (mean age: 62 ± 10 years) were included and functional abnormalities were detected in 93% of them. During follow-up (median of 1422 days; interquartile range, 1287-1634), 13.1% of the patients experienced at least one adverse cardiovascular event. Kaplan-Meier analysis revealed that patients with a CFR < 2 had a higher risk of events (Hazard Ratio, HR: 4.97, 95% Confidence Interval, CI, 1.32-18.75), whereas other parameters such as FFR, IMR, eCFR, and macrovascular endothelial function had no effect. A low CFR was an independent predictor of cardiovascular events, even after adjustment for age and traditional cardiovascular risk factors (adjusted HR: 6.62, 95% CI, 1.30-33.70). Conclusions: The presence of abnormal coronary microvascular function as measured by a CFR < 2 in the non-culprit territory predicts future risk of adverse cardiovascular events.