Coronary thrombosis is defined as the formation of a blood clot inside a blood vessel of the heart. This blood clot may then restrict blood flow within the heart, leading to heart tissue damage, or a myocardial infarction, also known as a heart attack.Coronary thrombosis is most commonly caused as a downstream effect of atherosclerosis, a buildup of cholesterol and fats in the artery walls. [Source: Wikipedia ]