An intravascular ultrasound appraisal of atherosclerotic plaque distribution in diseased coronary arteries

Background The assumption that atherosclerosis accumulates in the proximal coronary arteries and that distal segments are spared has yet to be systematically shown in vivo. Methods We used intravascular ultrasound to analyze complete proximal, mid, and distal segments from 75 diseased left anterior descending arteries (LADs) and 61 diseased right coronary arteries (RCAs) (including either the posterolateral [PLA; n = 38] or posterior descending artery [PDA; n = 23]) to document that distal coronary arteries are more often free of disease vs proximal vessels. External elastic membrane, lumen, and plaque and media areas were measured every 0.4 mm (median), and plaque burden (plaque and media/external elastic membrane) and percentage of normal (plaque and media thickness <0.3 mm) cross sections/segment were determined. Results Left anterior descending artery plaque was heaviest in proximal and mid segments, diminishing significantly in distal segments; plaque burden was 46% ± 9% in proximal, 39% ± 8% in mid, and 31% ± 9% in distal LAD (P < .0001), with 93% (median) of distal LAD cross sections being normal compared with 21% of mid and 0% of proximal cross sections (P < .0001). Right coronary artery plaque gradient was less pronounced vs the LAD; plaque burden was 37% ± 13% in proximal, 40% ± 10% in mid, and 36% ± 10% in distal RCA, followed by 31% ± 11% in PDA and 33% ± 10% in PLA. This was supported by the median percentage of normal cross sections/segment: 0% proximal, 0% mid, and 23% distal RCA sections plus 100% PDA and 48% PLA sections. Conclusions Intravascular ultrasound data indicated a proximal-to-distal LAD plaque gradient; significant disease was uncommon in the distal LAD. Conversely, the proximal-to-distal RCA plaque gradient was less distinct than the LAD, although disease in the PDA was still reduced compared with proximal segments.