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Background: Reperfusion in ST-elevation myocardial infarction (STEMI) improves survival. Moreover, early reperfusion can abort the infarct and avoid significant myocardial necrosis. Yet, limited real world data exist and comparison between reperfusion strategies has not been established., Methods: Using a comprehensive Canadian registry of consecutive STEMI patients, we prospectively collected serial electrocardiograms (ECGs) and clinical data from August 2006 to March 2011. Aborted myocardial infarction (AbMI) was defined as a maximal creatine kinase ≤ 2 times the upper limit of normal with evolutionary ECG changes of STEMI. ECG confounders and subjects with incomplete data were excluded., Results: Of the 2235 STEMI patients reperfused within 12 hours, 16.0% were considered to have an AbMI. Numerically, higher rates of AbMI with fibrinolysis vs primary percutaneous coronary intervention were reported (17.0% vs 14.7%; P = 0.15) with a temporal pattern seen up to 4 hours from symptom onset in favour of fibrinolysis (P trend < 0.001). Most notably, the highest frequency of AbMI was observed within the first hour with fibrinolysis (31.1%). Improved in-hospital outcomes (death/shock/congestive heart failure) were seen with AbMI (5.6% vs 13.6%; P < 0.001; adjusted odds ratio, 0.22; 95% confidence interval, 0.08-0.57)., Conclusions: In a large contemporary Canadian STEMI registry, AbMI appears to be common and associated with improved clinical outcome. Early reperfusion seems to enhance AbMI particularly when fibrinolysis is administered within 1 hour of symptom onset., (Copyright © 2014 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)