Ruptured plaque is associated with larger infarct size following successful percutaneous coronary intervention in ST segment elevation acute myocardial infarction.

Background: Pathological studies report that acute ST segment elevation myocardial infarction (STEMI) is caused not only by plaque rupture but also by other causes, such as erosion. To test our hypothesis that different lesion morphologies result in different clinical outcomes, we used intravascular ultrasound (IVUS) to investigate the relationship between lesion morphology and infarct size after successful primary angioplasty.

Methods: Our 72 consecutive first anterior STEMI patients underwent preintervention IVUS and were successfully recanalized with primary angioplasty. Using echocardiography, we analyzed left-ventricular wall motion to obtain a Wall Motion Score Index (WMSI) before angioplasty and 1 month after the onset, and used thallium myocardial scintigraphy 1 month after the onset to obtain computer-generated severity scores. Patients were divided into a rupture group (n = 30) and a nonrupture group (n = 42) on the basis of preintervention IVUS findings.

Results: Peak creatine kinase levels (3150+/-357 vs. 2256+/-238 IU/l, P = 0.03) and severity score (758+/-114 vs. 474+/-75, P = 0.03) in the rupture group were significantly higher. Despite there being no difference in baseline WMSI (1.55+/-0.04 vs. 1.58+/-0.03, P = 0.45), improvement in WMSI in the rupture group was significantly less pronounced (0.08+/-0.02 vs. 0.18+/-0.03, P = 0.01).

Conclusion: STEMI caused by plaque rupture is associated with a large degree of myocardial damage and poor functional recovery as compared with STEMI of different etiologies, even after successful primary angioplasty. Our results suggest that lesion morphology may affect clinical outcomes.