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

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Abstract

Background The purpose of this investigation was to quantify the amount of intralesional calcium detected by intravascular ultrasound (IVUS) compared with undecalcified histology in human arteries. This method preserves intralesional calcium and reduces sectioning artifacts, thereby providing an accurate measure of calcium plaque morphology. Methods and Results Ten arterial segments (5 coronary, 5 iliac) were obtained at autopsy. IVUS imaging was performed with a 4.9F catheter at an automated pullback rate of 1.0 mm/s. The undecalcified arteries were dehydrated in ascending alcohol and polymerized in glycol methylmethacrylate. The arteries were cut into 200-μm sections with an Isomet low-speed saw and stained with Goldner’s trichrome. The lumen cross-sectional area, the calcium plaque cross-sectional area, the calcium plaque depth, length, and angle of arc of calcified plaque were measured from the IVUS images and histologic sections. In 24 selected cross sections, there were 38 separate calcium plaques. An independent observer correctly identified 34 of 38 calcified plaques for a sensitivity of 89% and specificity of 97%. The total mean calcified plaque cross-sectional area measured from histology was 4.6 ± 4.1 mm2 compared with 2.8 ± 2.3 mm2 by IVUS (P = .002). Plaque depth measured by histology was 1.2 ± 0.4 mm versus 0.7 ± 0.2 mm by IVUS (P = .001). The length 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 because of the inability of the ultrasound to penetrate intralesional calcium, which leads to an underestimation of the depth of calcium by 45%. (Am Heart J 1999;137:482-8.)

Section snippets

Harvesting and imaging

Ten human atherosclerotic arterial segments (5 coronary, 5 iliac) from 6 cadavers (2 male, 4 female) ranging in age from 42 to 73 years (mean age 57.5 ± 12.9 years) were obtained from the Orange County Coroner’s Office and stored in formaldehyde until IVUS imaging. Although formaldehyde alters tissue characterization somewhat, calcium is such a strong reflector that recognition of calcium is not affected on the IVUS image. An acoustic reference was provided by 2 surgical needles placed through

Results

Twenty-four arterial cross sections were chosen for comparison with the IVUS images. These sections were chosen because they had homogeneous calcified plaques. In these 24 sections, there were 38 separate calcified plaques identified on histology. From the IVUS images, the independent observer correctly identified 34 of the 38 calcified lesions, for a sensitivity of 89%. The specificity in this cohort was 97%. A representative example of an IVUS image and the corresponding undecalcified

Discussion

This comparison study between histologic cross sections of human atherosclerotic arteries and IVUS images confirms the previously reported high sensitivity and specificity for the identification of calcified plaque by IVUS.3, 8, 9, 11, 12, 13 The unique feature of the current study is that GMA was used for the histologic preparation, which is a technique that does not require decalcification of the tissue. Embedding the arteries in this plastic produces durable cross-sectional cuts without

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Reprint requests: Jonathan M. Tobis, MD, UCI Medical Center, Division of Cardiology, 101 The City Dr, Bldg 53, Room 100, Orange, CA 92868-3298.

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0002-8703/99/$8.00 + 0   4/1/91288

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