IN-VITRO DIAGNOSIS OF CORONARY PLAQUE MOR PHOLOGY USING INTRAVASCULARULTRASOUND - COMPARISON WITH HISTOPATHOLOGIC FINDINGS

The aim of this study was to validate the accuracy of a commercially a vailable intravascular ultrasound system in diagnosing plaque composit ion in human coronary arteries. Thirty-five coronary arteries of 18 hu man autopsy hearts were perfused with NaCl under a pressure of 100 mm Hg and examined using a Diasonics ultrasound system and 4.8 F 20 MHz c atheters. An ultrasound diagnosis was made ot 139 coronary sections us ing previously published standard criteria and compared with histologi c findings. In addition, the influence of the histologic pattern of li pid and calcific deposits on the accuracy of the ultrasound diagnosis was evaluated. Of the 25 sections with a histologically normal intima, 14 (56%) were correctly identified by ultrasound, whereas fibrotic th ickening was diagnosed in the remaining 11 sections. There were 114 pl aques by histology which were correctly visualized by ultrasound as pl aques in all instances. Plaque calcification was correctly diagnosed i n 54 of 63 (86%) sections, but massive calcifications were more reliab ly identified by ultrasound than small speckled calcifications (43/44 = 98% vs 11/19 = 58%, p < 0.001). Fibrosis was present in all 114 plaq ues and was correctly visualized by ultrasound in all instances. When lipid was diagnosed by ultrasound as a homogeneous zone of low signal intensity within a fibrous plaque as suggested in the literature, lipi d accumulations were identified with a sensitivity of 26% (16/62) and a specificity of 92% (71/77). When lipids were diagnosed if more than a quarter of the plaque area showed lower signal intensity than the ti ssue surrounding the vessel, the sensitivity of ultrasound was improve d to 73% (45/62) but specificity fell to 30% (23/77). The entire histo logic composition of a section was correctly diagnosed by ultrasound i n only 42% of the 139 sections. Further technical improvements are the refore mandatory before intracoronary ultrasound will be able to provi de a reliable analysis of plaque composition, especially of the lipid content.