Two‐Dimensional Visualization of Cholesterol and Cholesteryl Esters Within Human Coronary Plaques by Near‐Infrared Fluorescence Angioscopy

Abstract

Cholesterol (C) and cholesteryl esters (CE) within coronary plaques are minimally visualized directly by any of the available imaging modalities in vivo. If they are rendered visible in vivo, the progression of coronary plaques and the effects of respective therapies on these plaques can be objectively evaluated. The C and CE within human coronary plaques can be visualized by near-infrared fluorescence angioscopy (NIRFA). By exciting at 710 ± 25 nm and emitting at 780 nm, near-infrared fluorescence (NIRF) of lipid components was examined by microscopy in vitro. Lipid components in 49 plaques of 32 excised human coronary arteries were examined by NIRFA in vitro. Coronary plaques were examined by NIRFA in 25 patients with coronary artery disease. C, CE, and calcium (Ca) individually did not exhibit NIRF but did in the presence of β-carotene, which is known to coexist with lipids in the vascular wall. Other substances that are contained in atherosclerotic plaques did not.² The excised human coronary plaques were classified as those with NIRF and those without. The former plaques were classified into homogenous, doughnut-shaped, and spotty types. Histological examinations revealed that these image patterns were determined by the differences in the locations of C, CE, and Ca, and that those deposited within 700 μm in depth from the plaque surface were imaged by NIRFA. Homogenous, doughnut-shaped, or spotty NIRFA images were also observed in patients. NIRFA is feasible for 2-dimensional imaging of C and CE deposited in human coronary plaques.