Pathophysiology and medical management of angina pectoris

Myocardial oxygen demand is a function of the product of heart rate and blood pressure. Agents such as nitroglycerin not only produce coronary vasodilatation, which increases oxygen supply, but also reduce myocardial oxygen demand secondary to a reduction in both preload and afterload. Beta-adrenergic blockers are useful in angina because they reduce myocardial work and, hence, oxygen demand. A heart rate in the 50s does not preclude an increase in the dosage of propranolol when necessary.