Impact of collateral flow on myocardial reperfusion and infarct size in patients undergoing primary angioplasty for acute myocardial infarction

Background The prognostic impact of baseline collateral flow of the infarct-related artery (IRA) in patients undergoing primary percutaneous coronary intervention (PCI) remains controversial. We sought to examine the impact of baseline collateral flow to the IRA on reperfusion success, infarct size, and clinical outcomes in patients undergoing primary PCI for acute myocardial infarction (AMI). Methods and Results Acute procedural, 30-day, and 6-month clinical outcomes were assessed after primary PCI among patients enrolled in the EMERALD trial (n = 501 with AMI within 6 hours of onset). Patients with collateral flow to the IRA (Rentrop grade 2 or 3) more commonly had prior stable angina, less commonly had failed thrombolysis and left anterior descending artery occlusion, and presented with less ST-segment elevation. Myocardial reperfusion assessed by ST-segment recovery and myocardial blush was similar in patients with and without baseline collateral flow to the IRA. Infarct size (assessed by technetium Tc 99m sestamibi) was similar among patients with and without baseline collateral flow in anterior infarction (mean 28.5% vs 31.2%, respectively; P = .59) and nonanterior infarction (12.5% vs 12.1%, respectively; P = .81). There were no differences in the rates of major adverse cardiac events at 30 days or 6 months according to baseline IRA collateral flow. Conclusions Among patients undergoing primary PCI for AMI within 6 hours of symptom onset, we found no significant relationship between baseline collateral flow and either reperfusion success, infarct size, or subsequent clinical outcomes.