Angiography-Derived Index of Microvascular Resistance in Patients With Anterior ST-Segment Elevation Myocardial Infarction After Successful Primary Percutaneous Coronary Intervention

Microvascular dysfunction following primary percutaneous coronary intervention (pPCI) is a well-established determinant of adverse outcomes in ST-segment elevation myocardial infarction (STEMI) patients. Although the invasive Index of Microcirculatory Resistance (IMR) has demonstrated prognostic value, its reliance on thermodilution limits its routine applicability. Angiography-derived functional indices, already validated in the epicardial domain, may offer a simplified, non-invasive alternative for microvascular assessment. To evaluate the prognostic performance of the angiography-derived Index of Microcirculatory Resistance (AngioIMR), we retrospectively analyzed 180 consecutive patients undergoing percutaneous coronary intervention (pPCI) for anterior STEMI at Fondazione Poliambulanza, Brescia, between January 1, 2016, and February 1, 2024. AngioIMR was computed using the formula: AngioIMR = MAP × QFR × TFC. The primary endpoint was a composite of all-cause death, target vessel myocardial infarction, or hospitalization for heart failure. The secondary endpoint additionally included hospitalization for angina. Over a 5-years follow-up, primary and secondary endpoints occurred in 16 (8.9%) and 23 (13%) patients, respectively. The optimal AngioIMR cut-off was 43 (AUC 0.800; 95% CI: 0.714–0.887; p <0.001), with sensitivity 87.5%, specificity 63.4%, PPV 18.9%, and NPV 98.1%. The incidence of both the primary and secondary endpoints were significantly higher in patients with AngioIMR ≥ 43: 18.9% versus 1.9% (p <0.001) and 28.4% versus 1.9% (p <0.001), respectively. AngioIMR ≥ 43 was associated with increased risk of adverse outcomes (HR: 9.5; 95% CI: 2.2–42.0; p <0.001), and remained an independent predictor at multivariable analysis. In conclusion, AngioIMR may be a promising tool to stratify prognosis in patients with STEMI.