Relationship Between Infarct Size and Outcomes Following Primary PCI: Patient-Level Analysis From 10 Randomized Trials

Background: Prompt reperfusion in patients with ST-segment elevation myocardial infarction (STEMI) reduces infarct size and improves survival. However, the intuitive link between infarct size and prognosis has not been convincingly demonstrated in the contemporary era.

Objectives: This study sought to determine the strength of the relationship between infarct size assessed early after primary percutaneous coronary intervention (PCI) in STEMI and subsequent all-cause mortality, reinfarction, and hospitalization for heart failure.

Methods: We performed a pooled patient-level analysis from 10 randomized primary PCI trials (total 2,632 patients) in which infarct size was assessed within 1 month after randomization by either cardiac magnetic resonance (CMR) imaging or technetium-99m sestamibi single-photon emission computed tomography (SPECT), with clinical follow-up for ≥ 6 months.

Results: Infarct size was assessed by CMR in 1,889 patients (71.8%) and by SPECT in 743 patients (28.2%). Median (25th, 75th percentile) time to infarct size measurement was 4 days (3, 10 days) after STEMI. Median infarct size (% left ventricular myocardial mass) was 17.9% (8.0%, 29.8%), and median duration of clinical follow-up was 352 days (185, 371 days). The Kaplan-Meier estimated 1-year rates of all-cause mortality, reinfarction, and HF hospitalization were 2.2%, 2.5%, and 2.6%, respectively. A strong graded response was present between infarct size (per 5% increase) and subsequent mortality (Cox-adjusted hazard ratio: 1.19 [95% confidence interval: 1.18 to 1.20]; p < 0.0001) and hospitalization for heart failure (adjusted hazard ratio: 1.20 [95% confidence interval: 1.19 to 1.21]; p < 0.0001), independent of age, sex, diabetes, hypertension, hyperlipidemia, current smoking, left anterior descending versus non-left anterior descending infarct vessel, symptom-to-first device time, and baseline TIMI (Thrombolysis In Myocardial Infarction) flow 0/1 versus 2/3. Infarct size was not significantly related to subsequent reinfarction.

Conclusions: Infarct size, measured by CMR or technetium-99m sestamibi SPECT within 1 month after primary PCI, is strongly associated with all-cause mortality and hospitalization for HF within 1 year. Infarct size may, therefore, be useful as an endpoint in clinical trials and as an important prognostic measure when caring for patients with STEMI.