Beta-adrenergic blockers have been shown definitely to reduce the incidence of total mortality, cardiovascular mortality, sudden death and nonfatal reinfarction in survivors of an acute myocardial infarction. The mechanisms to explain this protective action of beta blockers have never been elucidated conclusively, and include the antiarrhythmic and myocardial oxygen demand-reducing effects of the drugs. An antithrombotic mechanism has also been suggested. However, beta blockers have relatively weak antiplatelet activity, suggesting that their antithrombotic effects may be related to prevention of coronary artery plaque rupture and the subsequent propagation of an occlusive arterial thrombus rather than direct anticoagulant action. The therapeutic ability of beta blockers to attenuate the hemodynamic consequences of catecholamine surges, may protect a vulnerable atherosclerotic plaque from fracture, thereby reducing risk of coronary thrombosis, myocardial infarction and death.