What is primarily responsible for the majority of thrombi associated with ACS?

The majority of thrombi associated with acute coronary syndrome (ACS) are primarily caused by disrupted plaques that have ruptured. When atherosclerotic plaques in coronary arteries rupture, they expose the inner core of the plaque to the bloodstream. This exposure triggers a cascade of events, including platelet activation and coagulation, leading to thrombus formation. These thrombi can occlude coronary blood flow, resulting in ischemia or infarction of the cardiac tissues.

In contrast, stable plaques typically do not rupture and are less likely to cause acute events. Newly developed collateral circulation, while potentially beneficial, does not directly lead to thrombus formation associated with ACS. Fibrous tissue that repairs arterial lesions may contribute to vascular healing but does not account for the acute thrombotic events characteristic of ACS. Therefore, the correct answer reflects the critical role of disrupted plaques in the pathophysiology of this condition.