Review of Pharmacology - 9E (2015)

Cardiovascular System
ANGINA PECTORIS
Major symptom of angina is the chest pain that occurs due to imbalance between oxygen
supply and demand. Coronary arteries are the large conducting arteries that run epicardially
and gives collateral vessels to endocardial region. Blood flow to endocardium occurs mainly
during diastole. In angina, there is a fixed atherosclerotic narrowing of the coronary arteries.
At rest, the patient does not develop pain because demand is also less which can be met
even with reduced flow. However, during exercise or emotional stimuli, myocardial oxygen
requirement increases that result in anginal pain (because blood supply is fixed and cannot be
increased). Two major strategies for the treatment and prevention of angina are to decrease
the oxygen requirement or to increase the blood supply to the ischemic region.
Oxygen demand of the heart is increased by increase in heart rate, contractility and heart
size. Increase in myocardial fibre tension and ventricular pressure also increases oxygen
requirement. Increase in end diastolic pressure (more blood in left ventricle at the end of
diastole) increases the duration of systole and heart spends less time in the diastole. This may
further increase the chances of anginal attacks because coronary flow occurs mainly during
diastole. Beneficial effect of nitrates in classical angina is through the reduction of preload that leads
to less end diastolic pressure. Beta blockers and calcium channel blockers act by decreasing the
heart rate and contractility. Recently a new strategy developed for use in angina is to make
efficient utilization of substrates by the heart.
General Cardiovascular Pharmacology System
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