What causes thrombosis of the coronary arteries?

Arterioclerosis. Arteriosclerosis or plaque buildup in the wall of the coronary arteries will narrow the lumen to the point where there is flow restriction, then clot formation. The plaque may rupture, allowing a flap-like effect, blocking the lumen, resulting in clot formation. Trauma may cause a separation of the layers of the wall, and this dissection results in clot formation.
Cholesterol. For most cases, thrombosis of a coronary artery is superimposed on a cholesterol plaque. The plaque fractures and the contents of the plaque are exposed blood which results in clot formation (thrombosis).

Related Questions

Can a thrombosis of right coronary artery just lie there dormant not doing anything or nor causing harm?

RCA. The RCA supplies the right atrium and ventricle. A complete blockage will cause a major heart attack. A thrombosis is NOT a dormant situation. It is restricting flow. How much restriction guides therapy. At a minimum medical therapy would be necessary (aspirin, plavix, (clopidogrel) statins etc). Read more...
No. A thrombosis, or blood clot, does not "lie dormant". A thrombosis of the RCA would develop rather suddenly as a biochemical response to a cholesterol-based, calcium-coated plaque that "cracks". Just as when skin is cut, platelet blood cells and other chemicals come together to "heal" the break in the plaque by creating a thrombosis (clot) that can then block blood flow to cause a heart attack. . Read more...