Assessment of atherosclerotic plaques at coronary bifurcations with multidetector computed tomography angiography and intravascular ultrasound-virtual histology

We evaluated the distribution and composition of atherosclerotic plaques at bifurcations with intravascular ultrasound-virtual histology (IVUS-VH) and multidetector computed tomography (MDCT) in relation to the bifurcation angle (BA). In 33 patients (age 63±11 years, 79% male) imaged with IVUS-VH and MDCT, 33 bifurcations were matched and studied. The analysed main vessel was divided into a 5 mm proximal segment, the in-bifurcation segment, and a 5 mm distal segment. Plaque contours were manually traced on MDCT and IVUS-VH. Plaques with >10% confluent necrotic core and <10% dense calcium on IVUS-VH were considered high risk, whereas plaque composition by MDCT was graded as non-calcified, calcified, or mixed. The maximum BA between the main vessel and the side branch was measured on diastolic MDCT data sets. Overall the mean plaque area decreased from the proximal to the distal segment [8.5±2.8 vs. 6.0±3.0 mm2 (P<0.001) by IVUS-VH and 9.0±2.6 vs. 6.5±2.5 mm2 (P<0.001) by MDCT]. Similarly, the necrotic core area was higher in the proximal compared with the distal segment (1.12±0.7 vs. 0.71±0.7 mm2, P=0.001). The proximal segment had the higher percentage of high-risk plaques (13/25, 52%), followed by the in-bifurcation (6/25, 24%), and the distal segment (6/25, 24%); these plaques were characterized by MDCT as non-calcified (72%) or mixed (28%). The presence of high-risk and non-calcified plaques in the proximal segment was associated with higher BA values (71±19° vs. 55±19°, P=0.028 and 74±20° vs. 50±14°, P=0.001, respectively). The proximal segment of bifurcations is more likely to contain high-risk plaques, especially when the branching angle is wide.

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