Beta-adrenergic blockade in patients with myocardial infarction: Evolution, efficacy and controversy

Beta-adrenergic blockade was launched into the treatment of cardiovascular disease over half a century ago. The unique effects of these drugs in reducing myocardial oxygen demand, by attenuating heart rate, blood pressure, and myocardial contractility and their antiarrhythmic actions, conferred major benefits in conditions such as angina, hypertension and arrhythmias. During the pre-coronary reperfusion era, large randomized trials with β-blockers in patients with acute myocardial infarction revealed significant reductions in morbidity and mortality in the early and late phases of the disease. However, with the application of new therapeutic approaches including coronary reperfusion, hemodynamic assessment, and an increasing array of new drugs (antiplatelet agents, inhibitors of the renin-angiotensin-aldosterone axis) utilized in myocardial infarction patients, the efficacy of β-blockade in reducing mortality and complications appeared to be less than in earlier studies. For the past four decades, numerous investigations have addressed this question with resultant mixed answers, which are attributable to the variable study cohorts, specific β-blocker, dosage, associated therapy, and length of follow-up. At present, oral β-blockers are recommended (class I) in guidelines for management of patients with acute myocardial infarction. Intravenous β- blockade is restricted to consideration for patients with no hemodynamic dysfunction or risk factors for this complication. The β-blockers recommended in patients with infarction are carvedilol, metoprolol succinate, or bisoprolol, each of which is associated with decreased mortality in patients with heart failure.