Abstract 708: Plaque Type and Composition on Multislice Computed Tomography and Virtual Histology Intravascular Ultrasound in Relation to the Degree of Stenosis
Background: Imaging of coronary plaques has traditionally focused on evaluating the degree of stenosis, as risk for adverse cardiac events increases with stenosis severity. Nevertheless, plaque composition may also play an important role. However, relation between plaque composition and severity of stenosis remains largely unknown.
Objective: To assess plaque composition (non-invasively by multislice computed tomography (MSCT) angiography and invasively by virtual histology intravascular ultrasound (VH IVUS)) in relation to the degree of stenosis.
Methods: 78 symptomatic patients underwent MSCT (with identification of the presence of 3 plaque types; non-calcified, calcified, mixed) followed by invasive coronary angiography and VH IVUS. VH IVUS evaluated plaque burden and minimal lumen area, plaque composition (% fibrotic, fibro-fatty tissues, necrotic core, dense calcium) and plaques were classified into 4 types (fibrocalcific, fibroatheroma, thin cap fibroatheroma, pathological intimal thickening). For each plaque examined both with MSCT and VH IVUS, percent stenosis was evaluated by quantitative coronary angiography. Significant stenosis was defined as more than 50% stenosis.
Results: Overall, 43 plaques (19%) corresponded to significant stenosis. Of the 227 plaques analyzed, 70 were non-calcified plaques (31%), 96 were mixed (42%) and 61 were calcified (27%) on MSCT. The various plaque types on MSCT were equally distributed among significant and non-significant stenoses. VH IVUS identified that plaques with significant stenosis had significantly higher plaque burden (67±11 vs. 53±12%, p<0.05) and smaller minimal lumen area (4.6 (3.8 – 6.8) vs. 7.3 (5.4 –10.5) mm2, p<0.05). Interestingly, no differences were observed in fibrotic tissue, fibro-fatty tissue, dense calcium and necrotic core. Non-significant stenoses were significantly more frequently classified as pathological intimal thickening (46 (25%) vs. 3 (7%), p<0.05), although thin cap fibroatheroma (considered to represent more vulnerable plaques) were distributed equally (p=0.18).
Conclusion: No evident relation exists between the degree of stenosis and plaque composition or vulnerability, as evaluated non-invasively by MSCT and invasively by VH IVUS.