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

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.