Effect of Early Metoprolol on Infarct Size in ST-Segment–Elevation Myocardial Infarction Patients Undergoing Primary Percutaneous Coronary Intervention
Authors: Ibanez Borja , Macaya Carlos , Sánchez-Brunete Vicente , Pizarro Gonzalo , Fernández-Friera Leticia , Mateos Alonso , Fernández-Ortiz Antonio , García-Ruiz José M. , García-Álvarez Ana , Iñiguez Andrés , Jiménez-Borreguero Jesús , López-Romero Pedro , Fernández-Jiménez Rodrigo , Goicolea Javier , Ruiz-Mateos Borja , Bastante Teresa , Arias Mercedes , Iglesias-Vázquez José A. , Rodriguez Maite D. , Escalera Noemí , Acebal Carlos , Cabrera José A. , Valenciano Juan , Pérez de Prado Armando , Fernández-Campos María J. , Casado Isabel , García-Rubira Juan C. , García-Prieto Jaime , Sanz-Rosa David , Cuellas Carlos , Hernández-Antolín Rosana , Albarrán Agustín , Fernández-Vázquez Felipe , de la Torre-Hernández José M. , Pocock Stuart , Sanz Ginés , Fuster Valentin 
Published: September 2013

Background—
The effect of β-blockers on infarct size when used in conjunction with primary percutaneous coronary intervention is unknown. We hypothesize that metoprolol reduces infarct size when administered early (intravenously before reperfusion).

Methods and Results—

Patients with Killip class II or less anterior ST-segment–elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention within 6 hours of symptoms onset were randomized to receive intravenous metoprolol (n=131) or not (control, n=139) before reperfusion. All patients without contraindications received oral metoprolol within 24 hours. The predefined primary end point was infarct size on magnetic resonance imaging performed 5 to 7 days after STEMI. Magnetic resonance imaging was performed in 220 patients (81%). Mean±SD infarct size by magnetic resonance imaging was smaller after intravenous metoprolol compared with control (25.6±15.3 versus 32.0±22.2 g; adjusted difference, −6.52; 95% confidence interval, −11.39 to −1.78;
P
=0.012). In patients with pre–percutaneous coronary intervention Thrombolysis in Myocardial Infarction grade 0 to 1 flow, the adjusted treatment difference in infarct size was −8.13 (95% confidence interval, −13.10 to −3.16;
P
=0.0024). Infarct size estimated by peak and area under the curve creatine kinase release was measured in all study populations and was significantly reduced by intravenous metoprolol. Left ventricular ejection fraction was higher in the intravenous metoprolol group (adjusted difference, 2.67%; 95% confidence interval, 0.09–5.21;
P
=0.045). The composite of death, malignant ventricular arrhythmia, cardiogenic shock, atrioventricular block, and reinfarction at 24 hours in the intravenous metoprolol and control groups was 7.1% and 12.3%, respectively (
P
=0.21).

Conclusions—
In patients with anterior Killip class II or less ST-segment–elevation myocardial infarction undergoing primary percutaneous coronary intervention, early intravenous metoprolol before reperfusion reduced infarct size and increased left ventricular ejection fraction with no excess of adverse events during the first 24 hours after STEMI.

Clinical Trial Registration—

URL:
http://www.clinicaltrials.gov
. Unique identifier: NCT01311700. EUDRACT number: 2010-019939-35.