Segmental assessments of coronary plaque morphology and composition by virtual histology intravascular ultrasound and fractional flow reserve.

Fractional flow reserve (FFR) is an index for identifying functionally significant stenotic lesions. A FFR value of ≤0.75 is considered clinically significant and indicative of physiological ischemia. Focal lesions with 30-80 % stenosis by angiography with lesion lengths of less than 20 mm were selected from left anterior descending arteries of 74 patients. The analysis for the total lesion was processed first, and then each lesion was divided into three segments to assess the each segment. Data on plaque geometry and composition of two FFR groups, FFR ≤ 0.75 and FFR > 0.75, were compared by total and segmental analysis. Lesions with FFR ≤ 0.75 had more fibrofatty tissue (13.5 ± 7.4 vs. 10.2 ± 6.5%, p = 0.05) and less dense calcium (7.2 ± 5.3 vs. 11.9 ± 7.5%, p = 0.01) compared to lesions with FFR > 0.75. The content of necrotic core in mid segments was higher compared to proximal and distal segments (22.9 ± 10.6, 20.2 ± 10.9, 17.1 ± 11.2%, respectively, p = 0.032) in lesions with FFR > 0.75 but the difference was less obvious in lesions with FFR ≤ 0.75 (17.9 ± 9.9, 18.7 ± 9.9, 15.8 ± 9.0%, respectively, p = 0.533). Coronary lesions with FFR > 0.75 have larger content of dense calcium and slightly less fibrofatty tissue compared to lesions with FFR ≤ 0.75. While segmental plaque compositions for each segment show noticeable variations in lesions with FFR > 0.75 such as high concentrations of necrotic core in mid segment, these differences in each segment become obscure in FFR ≤ 0.75 and are evenly distributed across the lesion.