Successful reperfusion after acute ST-elevation myocardial infarction improves prognosis. Among the different electrocardiographic markers of reperfusion, sum ST resolution is considered the hallmark of reperfusion, but is cumbersome to use.

To assess the usefulness of a single lead ST resolution at 90 minutes after fibrinolysis compared with the sum ST resolution in predicting Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow, we used prospectively collected data from the Limitation of Myocardial Injury Following Thrombolysis in Acute Myocardial Infarction (LIMIT-AMI) study. All patients had electrocardiograms recorded at presentation and 90 minutes and a coronary angiogram 90 minutes after fibrinolysis.

Infarction artery patency was assessed in 238 patients with 4 different ST resolution criteria: single lead ST resolution ≥50% and ≥70% and sum ST resolution ≥50% and ≥70%. The most sensitive criteria for TIMI grade 3 flow was single lead ST resolution ≥50% (sensitivity rate, 70%; specificity rate, 54%), whereas sum ST resolution ≥70% was most the specific criteria (sensitivity rate, 45%; specificity rate, 79%). The proportion of patients with TIMI grade 3 flow was similar in all 4 ST resolution groups (P = .84). Pre-discharge infarction size and ejection fraction were also similar. No single lead or sum lead measure of ST resolution was significantly associated with an increased risk of death, heart failure, or reinfarction.

We propose that single lead ST-resolution ≥50% as an optimal electrocardiographic indicator for successful reperfusion 90 minutes after fibrinolysis. This simple electrocardiographic measure should be combined with bedside clinical and hemodynamic assessment to optimize decision making after fibrinolysis.