Extent and distribution of atherosclerotic plaque in relation to major coronary side-branches: an intravascular ultrasound study in vivo

BACKGROUND: The non-uniform extent and distribution of atherosclerotic plaque at bifurcations have been described by necropsy studies and they are related to local blood-flow disturbances. Systematic evaluation of plaque extent and distribution upstream and downstream of major coronary side-branches has not yet been evaluated in vivo. METHODS: We used intravascular ultrasound imaging in 41 patients with atherosclerotic disease to study the region of 73 major coronary side-branches at 2 mm increments proximal and distal to the side-branch (657 images: 73 at origin of side-branch; 292 proximal; 292 distal). The maximum (MXT) and minimum (MINT) plaque thickness and the plaque burden percentage (% PB) were measured in all the segments. The angle of distribution of maximum plaque thickness with respect to the origin of the side-branch was determined in each cross-section and assigned to S1 when located on the semicircle in the direction of the origin of the side-branch and to S2 when located on the opposite wall. RESULTS: The mean value of maximum plaque thickness and the plaque burden percentage were similar at the origin and in the two adjacent segments proximal and distal to the side-branch (1.0 +/- 0.48 mm, 1.06 +/- 0.48 mm and 0.98 +/- 0.48 mm; 45 +/- 19%, 46 +/- 19% and 44 +/- 18%). In distal sites of analysis, the plaque was more frequently eccentric in comparison to proximal sites (presence of an arc of plaque-free wall: 79% versus 62% in very distal and in very proximal sites respectively; p < 0.05). The prevalence of maximum plaque in S2 was higher at the origin (84%) and in adjacent distal segments (86%) as compared with the adjacent proximal segments (60%; p < 0.0001). CONCLUSIONS: The distribution of plaque is influenced by the origin of a major coronary side-branch in patients with coronary atherosclerosis: in distal sites the location of maximum plaque is almost always eccentrically distributed on the wall opposite the take-off.