The aim of this study was to examine the effect of coronary collateral flow before reperfusion on long-term clinical prognosis in patients with acute ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention. We studied 235 patients with STEMI within 12 hours after symptom onset. All patients had Thrombolysis In Myocardial Infarction grade < or =1 flow before percutaneous coronary intervention. Collateral flow was graded according to the Rentrop classification. Patients were categorized as having absent or poor collateral flow to the infarct-related artery (group A) or significant flow (group B). In 166 patients there was absent or weak collateral flow (group A), whereas 69 had significant flow (group B). Long-term follow-up was available in 227 patients (97%) at a median of 797 days. Overall, 25 patients died during the follow-up period, 22 patients (13.8%) in group A and 3 patients (4.4%) in group B (p = 0.04). A total of 12 (7.5%) nonfatal recurrent myocardial infarctions occurred in group A compared to 2 (2.9%) in group B (p = 0.18). The combined major adverse cardiovascular event end point (death or nonfatal reinfarction) showed a significantly lower event rate in group B (p = 0.02). Extensive collateral flow at baseline was a significant predictor for a favorable long-term clinical outcome on multivariable analysis after adjustment for established prognostic markers. In conclusion, the presence of a well-developed collateral network before mechanical reperfusion in patients with STEMI is associated with improved long-term survival and lower major adverse cardiovascular event rates.
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