The goal of this study was to characterize determinants of infarct size in the multicenter randomized Counterpulsation to Reduce Infarct Size Pre-PCI Acute Myocardial Infarction (CRISP-AMI) trial. Contemporary determinants of infarct size in patients presenting with acute anterior myocardial infarction without shock and undergoing percutaneous revascularization have been incompletely characterized. In CRISP-AMI, 337 patients with acute anterior ST segment elevation myocardial infarction but without cardiogenic shock at 30 sites in 9 countries were randomized to initiation of intra-aortic balloon counterpulsation before primary percutaneous coronary intervention versus standard of care. The primary outcome was infarct size as measured by cardiac magnetic resonance imaging 3 to 5 days after percutaneous coronary intervention. Of 337 randomized patients, complete periprocedural and infarct size data were available in 250 patients (74%). After a comparison of baseline characteristics to ensure no significant differences, patients with missing data were excluded. Using multiple linear regression of 23 variables, time from symptom onset to first device (β = 0.022, p = 0.047) and preprocedural Thrombolysis In Myocardial Infarction flow 0/1 (β = 15.28, p <0.001) were independent predictors of infarct size. Infarct size increased by 0.43% per 30 minutes in early reperfusion and by 0.63% every 30 minutes in late reperfusion. In conclusion, in patients with acute anterior ST elevation myocardial infraction without cardiogenic shock, total ischemic time and preprocedural Thrombolysis In Myocardial Infarction flow 0/1 were associated with increased infarct size as determined by cardiac magnetic resonance imaging. These findings underscore the importance of systems of care aimed at reducing total ischemic time to open infarct arteries.
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