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CHICAGO -- Bolus injections of metoprolol prior to stenting in patients with STEMI did not save heart muscle, researchers reported here.

In a randomized, placebo controlled trial of 683 STEMI patients scheduled for percutaneous coronary intervention (PCI), intravenous metoprolol prior to angioplasty did not reduce the infarct size compared with patients who injected with a matched placebo, said , of Isala Klinieken in Zwolle, the Netherlands, and lead author of the study.

Roolvink presented the results of EARLY-BAMI (Effect of Early Beta-blocker Administration before primary PCI in patients with ST-elevation Myocardial Infarction) as a late-breaking clinical trial at the meeting. The study results were also published online by the Journal of the American College of Cardiology.

Infarct size, as percentage of the left ventricle (LV), measured by MRI 30 days after PCI in 342 of the patients -- a little more than half of the study population -- found no significant difference: 15.3%±11.0% of LV versus 14.9% ± 11.5%, Roolvink said. Likewise there were no discernible differences in the heart's efficiency: 51.0% LV ejection fraction for metoprolol versus 51.6% in the placebo arm (P =0.62).

But a secondary endpoint, reduction in malignant arrhythmias, did demonstrate a numerical advantage: 3.6% versus 6.98% favoring metoprolol, approaching significance (P=0.050). And use of metoprolol did not increase the risk of adverse events.

STEMI patients who presented less than 12 hours from symptom onset with Killip I-II and no evidence of AV block were randomized to IV metoprolol (2x5 mg bolus) or matched placebo before primary PCI.

The study's primary endpoint was, according to the JACC report, "myocardial infarct size as assessed by magnetic resonance imaging (MRI) at 30 days. Secondary endpoints were enzymatic infarct size and incidence of ventricular arrhythmias. Safety endpoints included symptomatic bradycardia, symptomatic hypotension, and cardiogenic shock."

, editor-in-chief of JACC: Cardiovascular Interventions, told 麻豆传媒 that the approach used in the study -- bolus injections of metoprolol prior to PCI -- is not used in the U.S. Moreover, "in some patients who are tachycardic, it could be harmful."

Nonetheless, King noted that the utility of beta blockers (oral) in acute STEMI is worthy of investigation. "I still believe there are some select patients who may benefit."

In an editorial, also published by JACC, Duke's , stated that intravenous metoprolol does appear to be safe in patients who are Killip Class I/II.

And because there does appear to be some benefit for patients with ventricular arrhythmias, she wrote, "a more reasonable approach may be to conduct a definitive trial stratified by STEMI location and adequately powered for clinical outcomes, including death, recurrent myocardial infarction, and heart failure events."

Meanwhile, Newby added, "given strong evidence that they reduce morbidity and mortality and prevent adverse remodeling after myocardial infarction, every effort should be made to improve use of angiotensin converting enzyme inhibitors/angiotensin receptor blockers and beta-blockers, both early after reperfusion and at discharge."

Roolvink noted that in both arms the STEMI severity was not as great as had been anticipated, which he cited as a limitation of the study. Another limitation involved the inability to blind clinicians to heart rate and blood pressure measures, although MRI was conducted on a blinded basis.