Unstable Angina arise from a combination of potential mechanisms, including the following:

1. Decreased blood delivery to the downstream myocardium, often due to a partially occlusive thrombus overlying a disrupted atherosclerotic plaque, from microembolization of thrombus and plaque debris with resulting blockage of the distal microcirculation

2. Fixed severe narrowing caused by progressive atherosclerosis or in-stent restenosis resulting in sufficient collateral blood flow around the stenosis to prevent transmural infarction when a fully occlusive thrombosis occurs

3. Dynamic obstruction caused by intense vasospasm, often referred to as Printzmetal angina, cocaine-induced vasoconstriction, or other causes of vasoconstriction

4. Inflammatory or infectious initiators of arterial narrowing, plaque rupture, and/or thrombogenesis

5. Increased myocardial oxygen demand (fever, tachycardia, hyperthyroidism, and other hyperadrenergic states, elevations of left ventricular afterload from hypertension, severe aortic stenosis, hypertrophic cardiomyopathy) and reduced myocardial oxygen delivery (anemia, hypoxemia, hypotension) despite normal coronary arteries

Spontaneous coronary artery dissection is a rare cause of ACS and is often linked with hormonal imbalance in connection with pregnancy, connective tissue disorders such as Marfan and Ehlers-Danlos syndromes, or with thoracic aortic dissection

a>2 drinks/day in men, >1 drink per day in women and lighter-weight persons; 1 drink = 0.5 oz (15 mL) of ethanol: 12 oz beer, 5 oz wine, or 1.5 oz 80-proof whiskey.