Angina can be viewed as a problem of supply and demand. Drugs used in angina pectoris are those that either increase supply of oxygen and nutrients, or reduce the demand for these — or both.
Supply can be increased by: cardiac work and myocardial oxygen need by:
• dilating coronary arteries
• slowing the heart (coronary flow, uniquely, occurs in diastole, which lengthens as heart rate falls).
Demand can be reduced by:
• reducing afterload, (i.e. peripheral resistance), so reducing the work of the heart in perfusing the tissues
• reducing preload, (i.e. venous filling pressure); according to Starling's Law of the heart, workload and therefore oxygen demand varies with stretch of cardiac muscle fibres
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