Two-dimensional visualization of cholesterol and cholesteryl esters within human coronary plaques by near-infrared fluorescence angioscopy.

BACKGROUND: 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. HYPOTHESIS: The C and CE within human coronary plaques can be visualized by near-infrared fluorescence angioscopy (NIRFA). METHODS: 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. RESULTS: C, CE, and calcium (Ca) individually did not exhibit NIRF but did in the presence of ß-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. CONCLUSIONS: NIRFA is feasible for 2-dimensional imaging of C and CE deposited in human coronary plaques.

Imaging of subendocardial myocardial blood flow by dye-staining cardioscopy in patients with coronary artery disease.

This study was carried out to image subendocardial myocardial blood flow (SMBF) by dye-staining cardioscopy (DSC) in patients with coronary artery disease.In patients with epicardial coronary artery disease, SMBF plays a direct and critical role in determining the extent and severity of cardiac function and symptoms. If SMBF could be clinically imaged instantaneously, the effects of medical and interventional treatment on it can be directly evaluated. However, there are no clinically available methods for direct and real-time imaging of SMBF. Twenty-three patients [6 with chest pain syndrome (CPS); 3 with vasospastic angina pectoris (VSA); 9 with angina pectoris due to organic coronary stenosis (AP); 5 with old myocardial infarction OMI)] underwent DSC of the left ventricle by selective intracoronary injection of 1 mL of 2.5% Evans blue dye solution (EB). Five patients with acute myocardial infarction (AMI) underwent DSC before and after coronary stent deployment. The endocardial surface was stained diffusely blue with EB indicating normal blood flow in patients with CPS; stained in a patchy fashion indicating patchy blood flow in patients with VSA; and stained in a patchy fashion or not stained indicating patchy or no blood flow in those with AP and OMI. Myocardial staining with EB was observed after coronary stent deployment in all patients with AMI, indicating restoration of the SMBF. It is evident that SMBF could be imaged by DSC. This imaging modality is useful for the evaluation of therapies and accurate guidance of transendocardial therapies of the ischemic myocardium.

Detection of vulnerable coronary plaques by color fluorescent angioscopy.

OBJECTIVES: This study was carried out to detect vulnerable coronary plaques by color fluorescent angioscopy. BACKGROUND: Collagen fibers (CFs) mainly provide mechanical support to coronary plaques. Oxidized low-density lipoprotein (Ox-LDL) induces macrophage proliferation, which in turn destroy CFs while accumulating lipids. As such, demonstration of the absence of CFs, deposition of lipids, and the Ox-LDL may suggest plaque instability. METHODS: Fluorescence of the major components of the atherosclerotic plaques was examined by fluorescent microscopy using a 345-nm band-pass filter and 420-nm band-absorption filter (A-imaging). Fluorescence of Ox-LDL was examined using a 470-nm band-pass filter and 515-nm band-absorption filter (B-imaging) and Evans blue dye as an indicator. Fluorescence in 57 excised human coronary plaques was examined by A-imaging color fluorescent angioscopy. Oxidized LDL in 31 excised coronary plaques and in 12 plaques of 7 patients was investigated by B-imaging color fluorescent angioscopy. RESULTS: Collagen I, collagen IV, and calcium exhibited blue, light blue, and white autofluorescence, respectively. In the presence of beta-carotene which coexists with lipids in the vascular wall, collagen I and IV exhibited green, collagen III and V white, cholesterol yellow, cholesteryl esters orange fluorescence. Oxidized LDL exhibited reddish brown fluorescence in the presence of Evans blue dye. Therefore, coronary plaques exhibited blue, green, white-to-light blue, or yellow-to-orange fluorescence based on plaque composition. Histological examination revealed abundant CFs without lipids in blue plaques; CFs and lipids in green plaques; meager CFs and abundant lipids in white-to-light blue plaques; and the absence of CFs and deposition of lipids, calcium, and macrophage foam cells in the thin fibrous cap in yellow-to-orange plaques, indicating that the yellow-to-orange plaques were most vulnerable. Reddish brown fluorescence characteristic of Ox-LDL was observed in excised coronary plaques, as also in patients. CONCLUSIONS: Color fluorescent angioscopy provides objective information related to coronary plaque composition and may help identify unstable plaques.