Besides its protective effect against neutrophil-mediated injury at reperfusion, intravenous (IV)
metoprolol was recently shown to reduce the progression of ischemic injury in a pig model of
ST-segment elevation myocardial infarction (
STEMI). Here, we tested the hypothesis that IV
metoprolol administration in humans with ongoing
STEMI blunts the time‑dependent progression of ischemic injury assessed by serial electrocardiogram (ECG) evaluations before reperfusion. The METOCARD-CNIC trial randomized 270 anterior
STEMI patients to IV
metoprolol or control before reperfusion by
percutaneous coronary intervention (PCI). In 139 patients (69 IV
metoprolol, 70 controls), two ECGs were available (ECG-1 before randomization, ECG-2 pre-PCI). Between-group ECG differences were analyzed using univariate and multivariate regression models. No significant between-group differences were observed on ECG-1. On ECG-2, patients who received IV
metoprolol had a narrower QRS than those in the control group (84 ms vs. 90 ms, p = 0.029), a lower prevalence of QRS distortion (10% vs. 26%, p = 0.017), and a lower sum of anterior and total ST-segment elevation (10.1 mm vs. 13.6 mm, p = 0.014 and 10.4 mm vs. 14.0 mm, p = 0.015, respectively). Adjusted analysis revealed similar results. Significant associations were observed between ECG-2 variables and cardiac magnetic resonance imaging measurements (extent of myocardial
edema,
infarct size, microvascular obstruction, and left-ventricular ejection fraction) after
STEMI. In summary, IV
metoprolol administration before reperfusion ameliorates ECG markers of
myocardial ischemia in anterior
STEMI patients. These data confirm that IV
metoprolol is able to reduce ischemic injury and highlight the ability of ECG analysis to provide relevant real-time information on the effect of cardioprotective
therapies before reperfusion.