CHICAGO – Early intravenous administration of the beta-blocker metoprolol before primary percutaneous coronary intervention in patients with ST-segment elevation myocardial infarction (STEMI) was safe but did not reduce infarct size in the randomized, placebo-controlled Early-BAMI trial.
No difference was seen in infarct size, as measured by magnetic resonance imaging at 30 days, between 336 patients with STEMI who presented within 12 hours of symptom onset and were randomized to receive intravenous metoprolol (2 vials with 5 mg) before undergoing angioplasty, and 347 such patients who received placebo (left ventricular volume, 15.3% and 14.9%, respectively), Dr. Vincent Roolvink of Isala Hospital, Zwolle, the Netherlands, reported at the annual meeting of the American College of Cardiology.
No differences were seen between the groups for the secondary endpoints of blood flow from the left ventricle or levels of cardiac enzymes, Dr. Roolvink noted.
Further, while significantly fewer cases of ventricular arrhythmia occurred in the metoprolol patients (3.6% vs. 6.9%), this difference was not clinically significant, he said.
No significant differences were seen with respect to safety endpoints, including abnormally slow heart rate, low blood pressure, or cardiogenic shock.
The Early-BAMI subjects had a mean age of 62 years, and most (75%) were men. They were enrolled at centers throughout the Netherlands and Spain.
“In this nonrestricted STEMI population, early intravenous metoprolol before primary percutaneous intervention did not reduce infarct size,” Dr Roolvink said, noting that the findings follow conflicting results from prior studies, with some suggesting that beta-blockers could reduce heart attack severity or improve blood flow from the left ventricle when given to STEMI patients prior to angioplasty.
However only one randomized trial took place in the primary percutaneous coronary intervention era, and that trial – METOCARD-CNIC (Effect of Metoprolol in Cardioprotection During an Acute Myocardial Infarction) – involved only patients with STEMIs involving the anterior wall of the left ventricle (J Am Coll Cardiol. 2014;63:2356-62).
Early-BAMI (The Effect of Early Administration of Intravenous Beta Blockers in Patients with ST-elevation Myocardial Infarction Before Primary Percutaneous Coronary Intervention) was the first double blind, placebo-controlled international multicenter study to test this approach.
“Our results do not confirm the effect observed in the METOCARD-CNIC trial,” Dr. Roolvink said.
He noted, however, that the current findings are limited by the fact that study subjects had lower than expected overall heart attack severity.
Additional large randomized trials are needed to clarify whether early beta-blocker treatment is of benefit before angioplasty in STEMI patients. The safety profile, low cost of beta-blocker administration, and the reduction of acute malignant arrhythmias among those receiving beta-blocker treatment in the current trial should encourage the performance of additional larger trials, he said.
The findings were simultaneously published online (J Am Coll Cardiol. 2016 Apr 3. doi:10.1016/j.jacc.2016.03.522)
Early-BAMI was funded by the Dutch Heart Foundation and Medtronic. Dr. Roolvink reported having no disclosures.