Abstract Body (Do not enter title and authors here): Introduction:
Development of intramyocardial hemorrhage (IMH) in acute STEMI following reperfusion is estimated to affect 35-50% of patients. IMH is a lethal event as it contributes to larger MI size, compromised myocardial salvage, adverse left ventricular (LV) remodeling, lower LVEF, and consequential major adverse CV events post-MI. Whether coronary collateral circulation reduces the deleterious effects of IMH has not been investigated.
Hypothesis:
We hypothesized that coronary collaterals could reduce the extent of post-reperfusion IMH volume and offer cardioprotection to hemorrhagic MI patients.
Methods:
MIRON-CL (NCT05898425) recruited and studied STEMI patients (n=294) reperfused via PCI. Pre-PCI coronary angiography allowed for assessment of collateral vessels using the Rentrop grading system, from Grade 0 (no collaterals) to Grade III (complete collateral filling). Post-PCI cardiac MRI, performed 3 days later, was used to determine area affected (extent of myocardial edema) from T2 maps, extent of IMH from T2* maps and MI size from LGE as %LV. Statistical analyses were used to examine relationships between collateral grades, MI size, IMH, and area affected.
Results:
124 patients were hemorrhagic and 170 were non-hemorrhagic. Patients with no collaterals (Grade 0; CL-) exhibited significantly higher IMH volumes (7.41 ± 5.33% LV) compared to those with 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). Total area affected post-PCI was larger in CL- (37.62 ± 15.32% LV) compared to CL+ (21.48 ± 13.21% LV, p<0.001). Presence of collateral circulation (Grade>0 combined; CL+) was correlated with smaller MI sizes (CL-: 38.66 ± 14.63% LV vs. CL+: 19.84 ± 13.72% LV, p<0.001) and reduced MVO volumes (CL-: 8.07 ± 6.60% LV vs. CL+: 2.17 ± 2.35% LV, p<0.001). Patients with no collaterals had a significantly higher adj. risk of IMH (OR: 5.71, 95% CI: 3.16-10.33, p<0.0001).
Conclusion:
Coronary collaterals reduce post-reperfusion IMH volume in STEMI patients and provide significant cardioprotection: reductions in area affected, MVO and MI size. Insight into collateral grade offers opportunities to improve risk stratification and management of revascularized STEMI patients.