Angina is an episodic clinical syndrome due to transient myocardial ischemia. Ischemia refers to a lack of oxygen due to inadequate perfusion, which results from an imbalance between oxygen supply and demand[3].
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3. Kasper, Dennis L., Harrison, Tinsley Randolph. Harrison's Principles of Internal Medicine. 16th ed. New York: McGraw-Hill, Medical Pub. Division, c2005.