Effect of coronary collaterals on microvascular obstruction as assessed by magnetic resonance imaging in patients with acute ST-elevation myocardial infarction treated by primary coronary intervention.

The aim of this study was to determine whether angiographically visible collaterals before reperfusion are associated with beneficial effects on infarct size, microvascular obstruction, and left ventricular function as measured by magnetic resonance imaging (MRI) in patients with ST-elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI). We examined 235 patients with STEMI and symptoms <12 hours. All patients had Thrombolysis In Myocardial Infarction grade < or =1 flow before PCI. Collateral flow was graded according to Rentrop classification. Patients were divided in 2 groups; group A had absent or weak collateral flow and group B had significant flow. In 166 patients there was absent or weak collateral flow, whereas 69 had significant flow. Extent of microvascular obstruction was significantly smaller in group B at early MRI (3.3% vs 2.1% of left ventricle, p = 0.009). Infarct size measured by peak creatine kinase release showed smaller infarcts in group B (p = 0.02), whereas MRI infarct size showed a weak trend (p = 0.20). At 6 months, a strong trend toward a lower rate of death or nonfatal reinfarction could be seen in group B (4.5% vs 12.2%, p = 0.07). In conclusion, well-developed collaterals before reperfusion by PCI in patients with STEMI are associated with a protective effect on coronary microcirculation.