Heart Attack – What happens

The atherosclerotic plaque narrows the lumen of coronary artery leading to reduced blood supply to a specific segment in muscle wall of heart. Gradual narrowing of the affected artery in heart does not usually lead to  infarction because of development of collateral vessels. But, when the plaque ruptures or ulcerates, it becomes a focus for aggregation of platelets leading to clot (thrombus) formation and occlusion of the artery. This occlusion abruptly decreases the blood supply resulting in necrosis of the affected area (leading to infarction). The  extent of damage depends on area supplied by the involved artery, extent of occlusion, presence or absence of collateral vessels, spontaneous lysis (dissolution) of thrombus (or clot).