Coronary Collaterals Provide Cardioprotection in Hemorrhagic ST-elevation MI

Intramyocardial hemorrhage (IMH), evident in 30-50% of revascularized STEMI patients, contributes to adverse outcomes in patients with acute ST-elevation myocardial infarction (STEMI). The development of IMH following reperfusion therapy is linked to increased infarct size, reduced myocardial salvage, adverse left ventricular (LV) remodeling, decreased left ventricular ejection fraction (LVEF), and a higher incidence of major adverse cardiovascular events post-myocardial infarction (MI). Despite the significant impact IMH imposes on patient outcomes, whether coronary collateral circulation modulates the development and extent of IMH following reperfusion has not been investigated.

Methods:

The MIRON-CL (NCT05898425) trial prospectively enrolled 294 STEMI patients who underwent reperfusion via primary percutaneous coronary intervention (PCI). From pre-PCI coronary angiography we assessed the presence and extent of coronary collaterals using the Rentrop grading system, ranging from Grade 0 (no collaterals) to Grade III (complete collateral filling). CMR was performed three days post-PCI. T2 mapping acquired for quantifying the extent of myocardial edema in the infarct territory (Area Affected), T2* mapping for determination of IMH, and LGE to assess Infarct Size as a percentage of LV mass (gm). Statistical methods were used to assess the relationships between collateral grades, Infarct Size, IMH, and the Area Affected.

Results:

Among the 294 STEMI patients, 124 were identified to be hemorrhagic, while 170 were non-hemorrhagic. Patients without coronary collaterals (Grade 0; CL-) exhibited significantly higher IMH volumes (7.41 ± 5.33% LV) compared to those with coronary collaterals (Grade I: 5.23 ± 3.21% LV, Grade II: 3.11 ± 2.78% LV, Grade III: 2.05 ± 1.89% LV; p< 0.001). The total Area Affected post-PCI was larger in patients without collaterals (37.62 ± 15.32% LV) compared to those with collaterals (21.48 ± 13.21% LV, p< 0.001). Additionally, the presence of collateral circulation was associated with smaller Infarct Size (CL-: 38.66 ± 14.63% LV vs. CL+: 19.84 ± 13.72% LV, p< 0.001) and reduced microvascular obstruction (MVO) volumes (CL-: 8.07 ± 6.60% LV vs. CL+: 2.17 ± 2.35% LV, p< 0.001). The absence of collaterals was also associated with a significantly higher multivariate adjusted risk for IMH (OR: 5.71, 95% CI: 3.16-10.33, p< 0.0001).

Conclusion:

Coronary collateral circulation reduces the extent of IMH volume after reperfusion in STEMI patients, offering cardioprotection through smaller MI size and Affected Area. These findings emphasize the intrinsic patient-to-patient differences in the development of IMH and help identify the most vulnerable patients at risk of IMH prior to reperfusion therapy.

Coronary angiography and cardiac MRI findings from a clinical trial evaluating STEMI patients stratified by Rentrop collateral grades (Grade 0-3). The first two rows display coronary angiograms before (pre-PCI TIMI 0) and after PCI (post-PCI TIMI 3) for each collateral grade. The red boxes highlight areas of interest. The bottom two rows present corresponding cardiac MRI images using Late Gadolinium Enhancement (LGE) and T2* sequences. Arrows indicate regions of hemorrhagic infarction, with LGE showing hyperenhancement and T2* showing hypointensity. The data demonstrate a trend of decreasing hemorrhage and microvascular injury as Rentrop grades increase from 0 to 3, indicating the protective role of well-developed coronary collaterals.

Bar graph representing the volume of intramyocardial hemorrhage (IMH) as a percentage of left ventricular (LV) volume across Rentrop collateral grades 0-3 post-PCI in STEMI patients from a clinical trial dataset. The graph shows significantly higher IMH volumes in patients with lower Rentrop grades (Grade 0 and 1) compared to those with higher grades (Grade 2 and 3), with statistically significant differences marked by asterisks (*p < 0.05). Non-significant differences (ns) are also indicated. The data suggest that well-developed coronary collaterals (higher Rentrop grades) are associated with lower IMH and reduced microvascular damage following PCI.