Color fluorescent angioscopy reveals unstable plaques
MedWire News: Color fluorescent angioscopy (CFA) may assist in the objective identification of unstable plaques in patients with coronary artery disease (CAD), research suggests.
Yasumi Uchida (Japan Foundation for Cardiovascular Research, Funabashi) and colleagues obtained 40 post-mortem coronary arteries from 26 people who had died of conditions including CAD, cancer, and stroke.
Conventional angioscopy classifies plaques into white and yellow plaques, with yellow ones believed to be vulnerable.
Uchida et al found that plaques that were white on conventional angioscopy were blue under CFA. Comparing the CFA results with histologic analysis revealed that collagen I exhibited blue autofluorescence; hence, stable plaques containing large amounts of collagen I were blue under CFA. These plaques had no lipid deposits or foam cells and had normal collagen fibers.
During plaque development, collagen I is replaced by collagen III, IV, and V, and collagen fibers are broken down.
Under CFA, collagen IV was light blue, while collagen III and V did not autofluoresce. Beta-carotene, which associates with lipids in the vascular wall, exhibited orange autofluorescence and affected the fluorescence of other plaque elements, so that collagen I and IV were green, III and IV were white, cholesterol was yellow, and cholesterol esters were orange.
Oxidized low-density lipoprotein (ox-LDL) did not autofluoresce, but was reddish brown in the presence of Evans Blue dye.
Therefore plaques that were yellow under conventional angioscopy, and therefore thought to be unstable, fluoresced green, white to light blue, or yellow to orange under CFA.
Green plaques were rich in lipids but also had abundant collagen fibers and no foam cells, so Uchida and team consider these to be stable plaques.
White-to-light-blue plaques had abundant lipids, degenerated collagen fibers, and foam cells throughout the deep and superficial layers, and were therefore becoming unstable.
Yellow-to-orange plaques exhibited a lipid core and a thin fibrous cap containing lipids, calcium particles, and foam cells, but almost no collagen fibers.
“These plaques were therefore considered to be the most vulnerable ones,” say Uchida et al in the Journal of the American College of Cardiology: Cardiovascular Imaging.
Notably, ox-LDL was present in arterial normal segments that appeared normal on conventional angioscopy, suggesting that its deposition preceded that of other lipids.
“Molecular or chemical imaging by CFA provides much more objective information on vulnerable coronary plaques than conventional angioscopy,” conclude the researchers.
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By Eleanor McDermid