Calcified plaque cross-sectional area in human arteries: Correlation between intravascular ultrasound and undecalcified histology

Background The purpose of this investigation was to quantify the amount of intralesional calcium defected by intravascular ultrasound (IVUS) compared. with undecalcified histology in human arteries. This method preserves intr alesional calcium and reduces sectioning artifacts; thereby providing an ac curate measure of calcium plaque morphology. Methods and Results Ten arterial segments (5 coronary, 5 iliac) were obtain ed at autopsy. IVUS imaging was performed with,a 4.9F catheter at an automa ted pullback rate of 1.0 mm/s. The undecalcified arteries were dehydrated i n ascending alcohol and polymerized in glycol methylmethacrylate. The arter ies were cut into 200-mu m sections with an Isomet low-speed saw and staine d with Goldner's trichrome. The lumen cross-sectional area, the calcium pla que cross-sectional area, the calcium plaque depth, length, and angle of ar c,of calcified plaque were measured from the IVUS images and histologic sec tions. In 24 selected cross sections, there were 38 separate calcium plaque s. An independent observer correctly identified;34 of 38 calcified plaques for a sensitivity of 89% and specificity of 97%. The total mean calcified p laque cross-sectional area measured from histology was 4.6 +/- 4.1 mm(2) co mpared with 2.8 +/- 2.3 mm(2) by IVUS (P=.002), Plaque depth measured by hi stology was 1.2 +/- 0.4 mm verses 0.7 +/- 0.2 mm by IVUS (P =.001). The len gth of calcium plaques measured by histology was 3.6 +/- 1.78 mm versus 3.6 +/-: 1.5 mm for IVUS (r = 0.79). Conclusions IVUS accurately depicts circumferential calcified lesions with high sensitivity (89%) and specificity (97%). However, IVUS underestimates the total calcified plaque cross-sectional area by 39%. This is mainly beca use of the inability of the ultrasound to penetrate intralesional calcium, which leads to an underestimation of the depth of calcium by 45%.