Relationship Between Infarct Artery, Myocardial Injury, and Outcomes After Primary Percutaneous Coronary Intervention in ST-Segment–Elevation Myocardial Infarction

BACKGROUND: The extent to which infarct artery impacts the extent of myocardial injury and outcomes in patients with ST-segment–elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention is uncertain. METHODS AND RESULTS: We performed a pooled analysis using individual patient data from 7 randomized STEMI trials in which myocardial injury within 30 days after primary percutaneous coronary intervention was assessed in 1774 patients by cardiac magnetic resonance (n=1318) or technetium-99m sestamibi single-photon emission computed tomography (n=456). Clinical follow-up was performed at a median duration of 351 days (interquartile range, 184–368 days). Infarct size and outcomes were assessed in anterior (infarct vessel=left anterior descending) versus nonanterior (non–left anterior descending) STEMI. Median infarct size (percentage left ventricular myocardial mass) was larger in patients with anterior compared with nonanterior STEMI (19.7% [interquartile range, 9.4%–31.7%] versus 12.6% [interquartile range, 5.1%–20.5%]; P<0.001). Patients with anterior compared with nonanterior STEMI were at higher risk for 1-year all-cause mortality (6.2% versus 3.6%; adjusted hazard ratio [HR], 1.66 [95% CI, 1.02–2.69]; P=0.04) and heart failure hospitalization (4.4% versus 2.6%; adjusted HR, 1.96 [95% CI, 1.15–3.36]; P=0.01). Infarct size was a predictor of subsequent all-cause mortality or heart failure hospitalization in anterior STEMI (adjusted HR per 1% increase, 1.05 [95% CI, 1.03–1.07]; P<0.001), but not in nonanterior STEMI (adjusted HR, 1.02 [95% CI, 0.99–1.05]; P=0.19). The P value for this interaction was 0.04. CONCLUSIONS: Anterior STEMI was associated with substantially greater myonecrosis after primary percutaneous coronary intervention compared with nonanterior STEMI, contributing in large part to the worse prognosis in patients with anterior infarction.