Wakai A. Myocardial infarction (ST-elevation). Clin Evid. 2009 Jan 9.

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Comment
Most trials involving the use of beta-blockers in acute MI have been conducted predominantly in people considered to be at low risk of heart failure (because of the supposed deleterious effect of beta-blockers on left ventricular function), and many of these trials took place in the pre-thrombolytic era. Beta-blockers may reduce rates of cardiac rupture and ventricular fibrillation. This may explain why people older than 65 years and those with large infarcts benefited most, as they have higher rates of these complications. The trial comparing early versus delayed beta-blockade after thrombolysis was too small to detect an effect on mortality. [44]

Clinical guide:
Early use of beta-blockers reduces the risk of reinfarction, but increases the risk of cardiogenic shock. [43] It is therefore prudent after an acute MI to start beta-blockers in hospital only when the patient has become haemodynamically stable.