Abstract 9964: Plaque Morphology, Plaque Composition and Spatial Distribution of the Sites of Potential Vulnerability of Culprit Lesions Implicated in Acute Myocardial Infarction

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Background: The role of plaque morphology, composition, and spatial distribution in plaque rupture and coronary occlusion in patients suffering acute myocardial infarction (AMI) needs clarification. Using color-mapping iMAP intravascular ultrasound (iMAP-IVUS), we examined culprit lesions to clarify plaque morphology, plaque composition and spatial distribution of the sites of potential vulnerability. Methods: Sixty-eight culprit lesions in 64 consecutive AMI patients who underwent angiography and IVUS examinations before intervention were analyzed. Plaque morphology and composition were quantified and compared between totally occlusive (TO) (n=42) and non-TO lesions and between ruptured (n=27) and non-ruptured lesions. Results: Both the length and plaque burden (PB) of TO lesions were greater than those of non-TO lesions (54.16 ± 21.16 mm versus 40.01 ± 17.51 mm, respectively, p = 0.006; PB: 0.63 ± 0.07 versus 0.58 ± 0.08, respectively, p = 0.02). Ruptured lesions were coincident with significant vessel remodeling (vessel volume: 745.5 ± 41.3 mm3 versus 635.7 ± 33.5 mm3, p = 0.04) and plaque volume (450.0 ± 23.8 mm3 versus 387.7 ± 19.3 mm3, p = 0.046). Also, the lipidic volume was greater (57.6 ± 3.8 mm3 versus 46.9 ± 3.1 mm3, p = 0.03) and the necrotic volume (152.6 ± 12.1 mm3 versus 125.8 ± 9.8 mm3, p = 0.09) tended to be greater in ruptured lesions. Examination of the longitudinal distribution of the sites of recognized vulnerability, i.e., maximum necrotic area (maxNA), maximum PB (maxPB) and most severely narrowed (minimal luminal area, MLA) revealed that most maxNA sites and maxPB sites were proximal to MLA sites. Ruptures usually occurred very close to maxNA sites (average distance: 0.33mm, 44% were proximal to, 26% overlapped and 30% were distal to a maxNA site) and proximal to maxPB and MLA sites. Conclusion: Plaque morphology and composition play critical roles in plaque rupture and coronary occlusion. The maxNA sites are the sites most likely to rupture, and most ruptures occur proximal to maxPB sites and MLA sites.