Effect of intravenous metoprolol before hospital admission on chest pain in suspected acute myocardial infarction

Background The aim of this study was to describe the effect of intravenous metoprolol on the intensity of chest pain before hospital admission in pati ents with suspected acute myocardial infarction (AMI). Methods and Results Two hundred sixty-two patients with acute chest pain an d suspected AMI were randomly assigned before hospital admission to either 5 mg morphine plus metoprolol 5 mg x 3 intravenously or 5 mg morphine plus intravenous placebo. Chest pain was evaluated on a 10-grade scale before an d for 60 minutes after intravenous injection, One hundred thirty-four patie nts were randomly assigned to metoprolol and 128 to placebo. Among all pati ents randomized to metoprolol, the mean chest pain score was reduced by 3.0 +/- 1.9 arbitrary units (AU) from before to after intravenous injection co mpared with 2.6 +/- 2.1 AU for placebo (not significant). Among patients wi th on initially confirmed or strong suspicion of AMI, the corresponding fig ures were 3.1 +/- 1.8 AU for metoprolol and 2.2 +/- 1.6 AU For placebo (P = .02). Among patients with only a vague or moderate suspicion of AMI, there was no difference. The treatment was well tolerated. Conclusions When al patients were included in the analyses. there was no si gnificant difference with regard to reduction of chest pain in the patients randomly assigned to metoprolol compared with placebo. A retrospective sub group analysis indicated a beneficial effect of metoprolol among patients w ith an initially strong suspicion of or confirmed AMI. Further investigatio ns are warranted to confirm this finding.