Noninvasive characterization of plaque morphology using helical computed tomography.

BACKGROUND: Evidence suggests that atherosclerotic plaque composition and morphology are more important predictors of plaque stability and clinical behavior than the degree of vessel stenosis. Unfortunately, noninvasive methods of plaque characterization in situ using duplex ultrasound have been largely unsuccessful. We investigated the accuracy of helical computed tomography (HCT) in defining plaque morphology in patients undergoing carotid endarterectomy. METHODS: Candidates for endarterectomy were enrolled prospectively and underwent HCT with intravenous contrast injection. The attenuation values (in Hounsfield Units) of plaque features such as calcium, fibrous tissue, and lipid were measured and correlated with the tissue types seen on microscopic examination. Percent luminal stenosis derived from transverse HCT images was also compared to values obtained from duplex ultrasound. SETTING: Ambulatory patients referred to a tertiary, metropolitan medical center. RESULTS: A total of 21 out of 22 cases were suitable for comparison. Qualitatively, HCT accurately defined plaque features containing calcium, fibrous stroma, and lipid. Using tissue attenuation values (Hounsfield Units - H), HCT distinguished between lipid and fibrous stroma (means 39+/-12 H and 90+/-24 H, respectively, p<0.001). HCT-derived calculations of percent stenosis also correlated with the ultrasound data (p<0.001). CONCLUSIONS: HCT is an accurate, noninvasive means for studying detailed plaque morphology and composition. This technique provides the basis for further studies correlating plaque anatomy with clinical behavior.

Quantitative analysis of anastomotic intimal hyperplasia in paired Dacron and PTFE grafts.

The purpose of this investigation was to compare and contrast the occurrence and progression of anastomotic intimal hyperplasia in two commonly used prosthetic arterial grafts. Twenty paired carotid artery interposition grafts of Dacron and PTFE (polytetrafluoroethylene) were implanted in a canine model. The grafts were electively removed at intervals from one week to seven months or at the time of thrombosis. Areas of hyperplastic growth were determined at each anastomosis using a quantitative histologic technique. The number of grafts quantitatively evaluated was 16 Dacron and 12 PTFE, excluding all thrombosed grafts. In both materials, hyperplasia occurred to a significantly greater degree at the distal or downstream anastomosis as compared with the proximal or upstream anastomosis (Dacron P less than 0.001, PTFE P less than 0.05). Quantitative and qualitative evaluation of these two commonly used but different arterial grafts did not demonstrate a significant difference in the occurrence of anastomotic hyperplasia.