Cardioprotective Role of Coronary Collaterals in the Development of Intramyocardial Hemorrhage in ST-Segment Elevation MI Patients

Abstract

Background: Intramyocardial hemorrhage (IMH), evident in 40% of revascularized ST-segment elevation myocardial infarction (STEMI) patients, is a lethal determinant of MI size. IMH compromises myocardial salvage and drives major adverse cardiovascular events. Objectives: We sought to determine whether the presence and extent of coronary collaterals affect development of IMH in STEMI patients. Methods: The MIRON-CL trial (NCT05898425) enrolled 294 consecutive STEMI patients reperfused via primary percutaneous coronary intervention (PCI). All underwent pre-PCI angiography to determine Rentrop collateral grades (0: none; III: complete). Three days post-PCI cardiac magnetic resonance imaging quantified myocardial area at risk (T2 edema), IMH (T2∗), and MI (late gadolinium enhancement). Results: Among 294 patients, 124 had IMH and 170 did not. Patients with no collaterals (CL-, Grade 0) had higher IMH (7.41% ± 5.33% left ventricle) than those with collaterals (CL+; Grade I: 5.23% ± 3.21%, II: 3.11% ± 2.78%, III: 2.05% ± 1.89%; P < 0.001). Total area at risk post-PCI was larger in CL- (37.62% ± 15.32% left ventricle) than in CL+ (21.48% ± 13.21%; P < 0.001). Absence of collaterals correlated with larger MI (CL- 38.66% ± 14.63% vs CL+ 19.84% ± 13.72%; P < 0.001) and higher microvascular obstruction (CL- 8.07% ± 6.60% vs CL+ 2.17% ± 2.35%; P < 0.001). Patients without collaterals had a higher adjusted risk of IMH (OR: 5.71; 95% CI: 3.16-10.33; P < 0.0001). Conclusions: Extent of coronary collaterals is a determinant of IMH in revascularized STEMI. Since IMH is known to drive post-PCI infarct expansion, determination of collateral status has the potential to identify patients at high risk of infarct expansion. For these high-risk patients, novel targeted therapies to reduce IMH, limit post-MI infarct expansion, and improve outcomes should be further explored.