Clinical research: acute myocardial infarction
Aborted myocardial infarction in patients with ST-segment elevation: Insights from the assessment of the safety and efficacy of a new thrombolytic regimen-3 trial electrocardiographic substudy

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Abstract

Objectives

The investigators undertook a systematic, comprehensive analysis of the therapeutic response and clinical outcomes of reperfusion therapy for acute ST-segment elevation myocardial infarction (STEMI) in 5,470 patients from the Assessment of the Safety and Efficacy of a New Thrombolytic Regimen (ASSENT)-3 trial.

Background

Prompt effective reperfusion therapy for acute STEMI may attenuate major myocardial necrosis.

Methods

We prospectively collected sequential electrocardiographs and clinical data. Aborted myocardial infarction (MI) was defined as maximal creatine kinase ≤2× upper limit of normal coupled with typical evolutionary electrocardiographic changes.

Results

Of the patients, 727 (13.3%) had an aborted MI, with the highest frequency (25%) occurring in patients treated <1 h after symptom onset. As compared with MI patients, patients with aborted MI more often had complete ST-segment resolution at 60 min (56.3% vs. 30.2%, p < 0.001) and 180 min (61.5% vs. 53%, p < 0.001); they also had smaller infarct sizes based on QRS score at discharge (2.37 vs. 4.62, p <0 .001). Mortality in aborted MI patients compared with those who had true MI was 3.9% versus 4.6% at 30-day and 7.0% versus 7.4% at 1-year. The baseline-adjusted mortality was significantly lower in patients with aborted MI (odds ratio [OR] 0.76, 95% confidence interval [CI] 0.63 to 0.92, p = 0.005 for 30-day and OR 0.70, 95% CI 0.50 to 0.98, p = 0.035 for one year). A very low-risk subset was identified with ≥70% ST-segment resolution at 60 min whose 30-day and 1-year mortality was 1.0% and 2.7%, respectively, compared with 5.9% and 9.3% in aborted MI patients with <70% ST-segment resolution at 60 min (all p ≤ 0.002).

Conclusions

Prompt fibrinolytic treatment improved the likelihood of aborted MI. The subgroup with complete 60-min ST-segment resolution had the best clinical outcomes.

Abbreviations

ASSENT-3
Assessment of the Safety and Efficacy of a New Thrombolytic Regimen-3 trial
CABG
coronary artery bypass graft
CI
confidence interval
CK-MB
creatine kinase-MB fraction
ECG
electrocardiogram/electrocardiographic
MI
myocardial infarction
OR
odds ratio
PCI
percutaneous coronary intervention
STEMI
ST-segment elevation myocardial infarction

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Financial support: Boehringer-Ingelheim (Germany), Genentech (South San Francisco, California), Aventis (Bridgewater, New Jersey).