Immediate intravenous (up to 15mg) then oral metoprolol (200 mg daily) for patients with acute ST-segment myocardial infarction was compared to placebo in a multicentre RCT in China, with a total of 45 852 subjects. Metoprolol non-significantly reduced the prespecified primary outcome of death, reinfarction, or cardiac arrest (OR 0.96, 95% CI 0.90 to 1.01, p=0.1), and death alone (7.7% vs 7.8%, OR 0.99, 95% CI 0.92 to 1.05, p=0.69). There were fewer patients with reinfarction (2.0% with metoprolol vs 2.5% with placebo; OR 0.82, 95% CI 0.72–0.92; p=0.001) and ventricular fibrillation (2.5% vs 3.0%; OR 0.83, 0.75–0.93; p=0.001), but more deaths from cardiogenic shock (2.2% vs 1.7%, p=0.0002). In post-hoc analysis, there was net harm during days 0–1, and net benefit from day 2 onward.
Comment: The authors conclude that in haemodynamically unstable patients at high risk of cardiogenic shock the beta-blockers must either be deferred until haemodynamically stable situation or the beta-blocker should be very carefully uptitrated.