Background:
The underlying mechanisms for acute myocardial infarction (AMI) include plaque rupture (PR), plaque erosion (PE), and calcific nodule (CN). Recently, in vivo diagnosis of PE was reported in patients with acute coronary syndromes (ACS) using optical coherence tomography (OCT). However, the true incidence of erosion in patients with AMI remains unknown.
Aim:
The aims of this study were (1) to evaluate the incidence of PR, PE, and CN in patients with AMI during the acute phase and (2) to compare the detailed plaque morphology in all 3 groups using both OCT and intravascular ultrasound (IVUS).
Methods and Results:
In 77 patients with AMI, both OCT and IVUS were performed following manual aspiration thrombectomy. Culprit plaques were classified into PR, PE, and CN using the established OCT criteria. The frequency of PR, PE, and CN were 62.3%, 27.2%, and 6.5%, respectively. PE had significantly lower prevalence of thin-cap fibroatheroma (TCFA), thicker fibrous cap and smaller lipid arc. Compared to PR and PE, CN had greater calcification (Table). On IVUS, plaque eccentricity index was significantly greater in PE compared to the others. PR and PE showed greater plaque burden. The remodeling index was different among these 3 groups. 75.0% of PR had positive remodeling but none in CN. In contrast, CN had higher prevalence of negative remodeling. The prevalence of superficial spotty calcification was higher in PR than the other 2 groups.
Conclusion:
This combined OCT and IVUS study demonstrates that erosion was the underlying mechanism in 27.2% of patients with AMI. In eroded plaques, TCFA was rare and eccentricity index was significantly greater.
Stenting of Culprit Lesions in Unstable Angina Leads to a Marked Reduction in Plaque Burden: A Major Role of Plaque Embolization?