Aborted myocardial infarction after primary percutaneous coronary intervention: Magnetic resonance imaging insights from the Assessment of Pexelizumab in Acute Myocardial Infarction (APEX-AMI) trial

Background Aborted myocardial infarction (AbMI) in patients with ST-elevation MI defined by ST resolution with less than 2-fold elevation in biomarkers has been previously reported. We examined the association among AbMI, other metrics of infarct size, and left ventricular (LV) function defined by cardiac magnetic resonance (CMR). Methods A total of 5745 patients with ST-elevation MI enrolled in the APEX-AMI trial, and 73 who were part of the CMR substudy within 3 to 5 days of randomization were evaluated. Core laboratories analyzed electrocardiograms, angiograms, and CMR images. Results Aborted MI (peak creatine kinase/creatine kinase MB < 2x upper limit of normal) with typical evolutionary electrocardiogram changes was observed in 11% (437/3938) overall and in 19% (14/73) of patients within the CMR study. Patients with AbMI were older (62 vs 60 years, P = .003) and tended to achieve complete STE-resolution post-percutaneous coronary intervention (>= 70% resolution: 64% vs 32%; P = .076) compared with patients with MI. Cardiac magnetic resonance revealed that patients with AbMI had a smaller infarct size (4.7% vs 14.9% LV, P <.001), less "no reflow" (0.9% vs 1.7% LV, P = .017), enhanced LV function (ejection fraction 54.4% vs 46.5%, P = .064), smaller LV end-systolic volumes (46.5 mL vs 67.2 mL, P = .009), and less transmurality (21.4% vs 50.9% with at least 1 segment with > 75% wall thickness, P = .046) when compared with patients with MI. Conclusions Patients with AbMI had smaller subendocardial infarcts with enhanced LV size and function. Cardiac magnetic resonance provides corroborative evidence of AbMI and insights into its pathophysiology, specifically rapid successful reperfusion leading to limitation of the "wavefront" of infarct to the subendocardium. (Am Heart J 2013;165:226-33.)