Use of intravenous (IV) beta-blockers prior to a coronary angioplasty in patients with ST-segment elevation myocardial infarction (STEMI) did not reduce heart attack severity or improve blood flow from the left ventricle, researchers reported at the American College of Cardiology’s 65th Annual Scientific Session.

Vincent Roolvink, MD, the study’s lead author explained that beta-blockers have demonstrated improvement in survival, reduction in the risk of recurrent heart attack and life-threatening arrhythmias, and prevention of heart enlargement in patients with STEMI. Dr. Roolvink and colleagues conducted the first large, double-blind, randomized, placebo-controlled trial to examine whether IV beta-blockers before an angioplasty would further boost patient outcomes. 

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Data from two earlier studies had suggested giving IV beta-blockers to STEMI patients prior to an angioplasty could reduce the severity of a heart attack or improve blood flow from the left ventricle. For this study, EARLY-BAMI (Effect of Early Beta-blocker Administration before primary PCI in patients with ST-elevation Myocardial Infarction), 683 patients with acute STEMI symptoms of <12 hours duration were randomized to receive IV metoprolol or placebo prior to undergoing angioplasty. The primary endpoint was severity of the heart attack as measured by MRI at 30 days. 

At Day 30 of follow-up, the primary endpoint of heart attack severity measured by MRI was 15.3% of left ventricular volume on average in the beta-blocker group vs. 14.9% in the placebo group; the difference was not statistically significant. No significant differences were seen between the two treatment arms on blood flow from the left ventricle or levels of cardiac enzymes. 

Ventricular arrhythmias occurred in 3.6% of patients who received beta-blockers vs. 6.9% of those who received a placebo; this finding was statistically significant but did not result in a clinically significant difference. In addition, 16 patients in the beta-blocker treatment group experienced abnormally slow heart rate, low blood pressure, or cardiogenic shock vs. 21 patients in the placebo group; this difference was not statistically significant.

Overall heart attack severity among study patients was lower than expected, which may explain why beta-blocker treatment did not appear to provide benefit. Dr. Roolvink called for more randomized trials to clarify whether IV beta-blocker treatment before an angioplasty offers benefit for STEMI patients.

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