Unstable angina pathophysiology & etiology


 * Associate Editors-In-Chief: ; Varun Kumar, M.B.B.S.; Lakshmi Gopalakrishnan, M.B.B.S.

The Pathophysiology of Unstable Angina Pectoris
Unstable angina occurs when myocardial oxygen demand exceeds myocardial oxygen supply at rest or with minimal exertion. This supply / demand mismatch can be caused by the following:

Conditions That Decrease Oxygen Supply

 * Coronary thromboembolism in which there is rupture at the shoulder of a lipid laden, inflamed coronary artery plaque with formation of thrombus and distal embolization is the classic cause of unstable angina. The artery is open, so there is no ST elevation to suggest transmural injury. Embolization may yield subendocardial ischemia which results in ST segment depression.
 * Dynamic obstruction (e.g., coronary artery spasm or coronary vasoconstriction) of epicardial and/or microvascular vessels
 * Prinzmetal's angina of the large epicardial coronary arteries
 * Syndrome X of the small downstream coronary microvasculature


 * Coronary artery disease progression with a severe, lipid laden, atherosclerotic stenosis
 * Myocardial bridge
 * Vasculitis of the coronary arteries
 * Coronary artery dissection
 * Anomalous left coronary artery passing between the aorta and pulmonary artery
 * Embolization into coronary arteries)
 * Anemia
 * Hypoxemia
 * Polycythemia

Conditions That Increase Myocardial Oxygen Demand

 * Amphetamine use
 * Aortic stenosis
 * Aortovenous shunts
 * Cocaine use
 * Congestive heart failure
 * Fever
 * High cardiac output
 * Malignant hypertension
 * Obstructive cardiomyopathy
 * Pheochromocytoma
 * Supravalvular aortic stenosis
 * Tachyarrhythmias (e.g., atrial fibrillation or atrial flutter)
 * Thyrotoxicosis

==Features of Pain, which are not Characteristic of Myocardial Ischemia ==


 * Pain which radiates into the lower extremities
 * Pleuritic pain (sharp or knife like pain brought on by respiratory movements or cough)
 * Primary or sole location of discomfort in the middle or lower abdominal region
 * Pain that may be localized at the tip of one finger, particularly over the left ventricular apex or a costochondral junction
 * Pain reproduced with movement or palpation of the chest wall or arms
 * Very brief episodes of pain that last a few seconds or less

==Braunwald clinical classification of unstable angina ==