Correlation between high frequency intravascular ultrasound and histomorphology in human coronary arteries

Abstract

Objective-To test the eYcacy of high frequency intravascular ultrasound (IVUS) transducers in identifying lipid/necrotic pools in atherosclerotic plaques. Methods-40 MHz transducers were used for in vitro IVUS assessment of 12 arterial segments (10 coronary and two carotid arteries, dissected from five diVerent necropsy cases). IVUS acquisition was performed at 0.5 mm/s after ligature of the branching points to generate a closed system. Lipid/necrotic areas were defined by IVUS as large echolucent intraplaque areas surrounded by tissue with higher echodensity. To obtain histopathological sections corresponding to IVUS cross sections, vessels were divided into consecutive 3 mm long segments using the most distal recorded IVUS image as the starting reference. Samples were then fixed with 10% buVered formalin, processed for histopathological study, serially cut, and stained using the Movat pentacrome method. Results-122 sections were analysed. Lipid pools were observed by histology in 30 sections (25%). IVUS revealed the presence of lipid pools in 19 of these sections (16%; sensitivity 65%, specificity 95%). Conclusions-In vitro assessment of lipid/necrotic pools with high frequency transducers was achieved with good accuracy. This opens new perspectives for future IVUS characterisation of atherosclerotic plaques. (Heart 2001;85:567-570) Keywords: intracoronary ultrasound; atherosclerosis; plaque morphology Coronary intravascular ultrasound (IVUS) provides quantitative information on lumen and vessel dimensions and plaque severity, as well as qualitative information on plaque composition in terms of hard and soft components and calcification. Previous IVUS studies on plaque composition, mainly performed in the early 1990s with 20-30 MHz transducers, showed that the technique defines calcification with high sensitivity and specificity, but is less accurate in assessing soft tissue components. [1][2][3][4][5][6][7][8][9] Thus, although 20 and 30 MHz transducers achieved appropriate definition of plaque morphology, the imaging of details such as the lipid pool and the fibrous cap remained poorly defined. No data are available on the characterisation of plaque morphology with high frequency transducers, which should allow more accurate definition of the soft components of the plaques.In this study we correlated corresponding IVUS and histopathological findings in human arterial specimens obtained at necropsy from patients with atherosclerosis, to determine how accurately 40 MHz IVUS can identify lipid/ necrotic pools. MethodsWe performed in vitro IVUS assessments, using continuous pull back, in arterial segments dissected from necropsy hearts. Arterial samples were serially sectioned in relation to IVUS markers. We then correlated the quantitative and qualitative evaluations of lipid/ necrotic pools obtained from histopathological slides with those obtained from IVUS cross sections. SAMPLE SERIESThe pathological series comprised 12 full length arteries, 10 coronary arteries (one left main, four left anterior...

Intravascular Palpography for High-Risk Vulnerable Plaque Assessment

“…Furthermore, calcified and noncalcified plaque components can be identified. However, the sensitivity to identify fatty plaque components remains low [8,9]. Recent rf-(radiofrequency) based tissue identification strategies appear to have better performance [9,10].…”

“…However, the distribution of the strain in the three-dimensional (3-D) geometry of an artery is an important tool to identify the presence of high-strain spots, their amount and distribution. Especially, since the correlation between plaque vulnerability and parameters provided by the echogram is low [8,9] selection of cross-sections based on the IVUS echogram introduces selection bias and increases the chance to miss the vulnerable spot. Additionally, during longitudinal monitoring of patients it is extremely difficult to refind the same spot after some months.…”

Identification of Atherosclerotic Plaque Components With Intravascular Ultrasound Elastography In Vivo

“…However, the sensitivity and specificity to detect lipid cores remains low. 3,4 IVUS elastography assesses the local radial strain in the tissue caused by an intraluminal pressure differential. In vitro experiments revealed different strain values in fibrous and fatty plaques in human coronary and femoral arteries.…”

Computer assisted three-dimensional plaque characterization in intracoronary ultrasound studies

“…Fibrous plaque can now be characterized as tissue that has a density that is similar or higher than that of the adventitia and hence will appear in grey levels that are mainly higher than that of the mean grey value of the adventitia [5][6][7]. Analogous, softer material has a lower grey value.…”

“…Studies that compared histology to intravascular ultrasound learned that different structures correspond to different video-densities in the images; structures that appear white indicating high echogenicity, mainly consist of dense fibrous or calcific tissue. The darker, echolucent or hypoechogenic areas contain larger amounts of loose fibrous or smooth, muscle-rich tissue and thrombotic or necrotic elements [5]. Based on this idea, video-densitometry can be used for plaque characterization [7].…”