1. Which of the following best describes the most common pathophysiologic mechanism present during ST segment elevation myocardial infarction?

A. Coronary plaque erosion

B. Coronary plaque rupture

C. Coronary plaque progression causing progressive stenosis

D. Coronary vasospasm

Plaque rupture and plaque erosion (ulceration) can result in coronary thrombosis. ST segment elevation MI is most often from coronary thrombosis after plaque rupture and less often from fixed obstruction. Unstable angina has a lower incidence of coronary thrombosis (compared with non-STEMI or STEMI) and is more often the result of fixed atherosclerotic stenosis. The predominant mechanism in non-STEMI and STEMI is plaque rupture (most common) or erosion resulting in coronary occlusion.