Abstract 568: Coronary Artery Plaque Spatial Distribution Matches that of Thrombosis in STEMI, and is Underestimated by Calcified Plaque Segments Alone
Angiographic studies of ST-elevation myocardial infarction (STEMI) show that occlusive thrombi occur in coronary arteries within the proximal third of each major vessel, within about 35 mm from the ostium. These findings suggest that these high-risk regions are sites of plaque vulnerability. Multidetector CTA (MDCTA) visualizes not only lumen but also calcified and uncalcified coronary plaque. We therefore studied the distribution of coronary plaque in patients to determine plaque distribution to compare result with location of angiographic myocardial infarction thrombus.
Methods: 48 outpatients (mean age 57 +− 5) undergoing Dual Source MDCTA (asymptomatic or with atypical symptoms) were studied. Most distal plaque location was measured for ostial-termination distance and composition (calcified/noncalcified) determined by one expert observer using validated, commercial plaque characterization software for lesion location and lesion length.
Results: Location of the most distal plaque was as follows, LAD (n=35) 31.8 mm, LCX (n=21) 33.0 mm, and RCA (n=24) 56.0 mm. Mean lesion lengths were LAD 19.4 +− 13.4 mm, LCX 15.1 +− 9.6 and RCA 18.4 +− 9.8 mm. Mean volume (cu mm) for calcified and noncalcified plaque was 130 +− 176 and 204 +− 249 respectively, for a ratio of 0.64. There was no propensity of either calcified or uncalcified plaque to aggregate longitudinally in the arteries.
The distribution and location of coronary artery plaque by MDCTA identically matches the known location of coronary artery vulnerability determined by angiographic studies. This finding suggests that STEMI does not occur in distal coronary locations simply because little plaque occurs in these areas.
Calcified plaque volume measured in 3-dimensions underestimates total plaque volume by a factor of 2.6. Calcific plaque is thus the ‘tip of the iceberg’.