Beta-blockers have been shown to prevent fatal and non-fatal heart attacks and sudden cardiac death. (The salutary effects of beta-adrenergic blockade are depicted in Fig. 1. A decrease in heart rate increases the diastolic interval during which the coronary arteries are filled with blood.
The coronary arteries are squeezed during systole and blood flow is restricted. Thus beta-blockers increase oxygen supply to the myocardium. This major beneficial effect has not been given prominence by workers in the field.
Beta-blockers decrease the force and velocity of cardiac contraction and decrease the heart rate pressure product (RPP). This action decreases myocardial oxygen demand and is important in the relief of angina.
It is interesting to note the good effect of beta-blockers on the arterial system. The thousands of miles of arteries are constantly under pressure from the pulsatile force and velocity of blood as well as blood pressure. The decrease in cardiac ejection velocity and a decrease in hemodynamic stress on the arterial wall, especially at the branching of arteries, may decrease the atherosclerotic process and plaque rupture. Atherosclerosis is commonly seen where arteries divide. Beta-blockers reduce blood pressure as well as the force and velocity of blood flow at these dividing points of mechanical stress and provide some protection from vessel wall injury. This favorable effect is of paramount importance in patients with high blood pressure. Mechanical injury from the velocity and force of blood is the prime cause of vessel wall injury, which leads to atherosclerosis, dissection of the plaques of atheroma and subsequent thrombosis, as well as rupture of an aneurysm (see the chapter Aneurysm).

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