Objectives: Coronary collaterals have been shown to protect ischemic myocardium from necrosis in patients with acute myocardial infarction (AMI). We sought to determine the impact of collateral circulation on infarct size in AMI using serial cardiac magnetic resonance (CMR).
Methods: A total of 46 anterior AMI patients (age, 58.9+/-10.6 years; male 72.3%) undergoing primary percutaneous coronary intervention (PCI) were investigated. The infarct size was measured on serial CMR performed within 7 days after primary PCI (acute stage) and 3 months later (chronic stage).
Results: Thirty-four patients (73.9%) showed collateral flow before primary PCI. CMR taken at the acute stage showed no significant difference in infarct size between two groups. However, follow-up CMR revealed significantly smaller percentage of infarct thickness (51.8+/-14.0 vs. 62.5+/-11.7%, P = 0.035) and mass (22.3+/-9.9 vs. 30.9+/-11.6%, P = 0.042) in patients with collaterals. There were significant changes from the acute to chronic stage regarding left ventricular end-systolic (-18.2+/-10.0 vs. 0.8+/-2.5 ml, P = 0.022) and end-diastolic volume (-14.8+/-9.2 vs. 2.6+/-13.7 ml, P = 0.031), percentage of infarct mass (-6.1+/-2.8 vs. -0.8+/-1.1%, P = 0.034), and thickness (-8.9+/-3.3 vs. -3.1+/-2.8%, P = 0.029) in collateral group compared with noncollateral group on serial CMR.
Conclusion: Serial CMR revealed the effect of collaterals in patients with AMI on reduction of infarct size and improvement of myocardial remodeling at the chronic stage.