Molecular Imaging of Native Low-Density Lipoprotein by Near-Infrared Fluorescent Angioscopy in Human Coronary Plaques

INDOCYANINE GREEN ANGIOGRAPHY OF TYPE 1 MACULAR NEOVASCULARIZATION IN AGE-RELATED MACULAR DEGENERATION AND CENTRAL SEROUS CHORIORETINOPATHY REVEALS DIFFERENT DISEASE MECHANISMS

PURPOSE

To assess the rate of late phase hyperfluorescent plaque (LPHP) in Type 1 macular neovascularization (MNV) in central serous chorioretinopathy (CSCR) and age-related macular degeneration (AMD) and to evaluate its prognostic value.

METHODS

Retrospective study including Type 1 MNV in AMD and CSCR, from 2012 to 2020. Eyes with a late indocyanine green angiography image (>20 minutes) and clear visualization of MNV on optical coherence tomography angiography (OCTA) were included. Quantitative and qualitative parameters on optical coherence tomography and best-corrected visual acuity were recorded at baseline and after three monthly antivascular endothelial growth factor injections.

RESULTS

Eighty-three eyes were included, 35 with CSCR and 48 with AMD. Patients in the CSCR group were significantly younger than in the AMD group (61.3 ± 10.4 vs. 80.2 ± 6.8 years, respectively, P < 0.001), predominantly male (68.6% CSCR vs. 35.4% AMD; P = 0.003), and with a thicker choroid (379 ± 93.3 µ m vs. 204.2 ± 93.2 µ m; P < 0.001). Type 1 MNV in CSCR showed fewer LPHP compared with AMD (31.4% vs. 77.1%; P < 0.001). The baseline visual acuity was lower in patients with LPHP (0.37 ± 0.22 vs. 0.27 ± 0.28 logarithm of the minimum angle of resolution, P = 0.03). On multivariate analysis, AMD was associated with the presence of LPHP ( P < 0.001). No significant difference in the response to antivascular endothelial growth factor was observed.

CONCLUSION

Leakage of macromolecules from MNV and accumulation in the retinal pigment epithelium and/or in the stroma imaged by the LPHP is less common in eyes with Type 1 MNV in CSCR than in AMD. Late phase indocyanine green angiography imaging offers an insight into the metabolism of the dye and the environment surrounding the neovascular membrane.

High-Resolution Scanning Fiber Angioscopy as an Adjuvant to Fluoroscopy During Endovascular Interventions

PURPOSE

To demonstrate the feasibility and potential utility of high-resolution angioscopy during common endovascular interventions.

METHODS

A 3.7-F scanning fiber angioscope was used in 6 Yorkshire pigs to image branch vessel selection, subintimal dissection, wire snaring, and stent placement. The angioscope was introduced in a coaxial fashion within a standard 6-F guide catheter. A clear field of view was provided using continuous heparinized saline flush through the outer guide catheter. The flush flow rate was manually adjusted to provide clear imaging depending on the diameter of the vessel and local blood flow conditions.

RESULTS

The scanning fiber angioscope was compatible with off-the-shelf catheters and devices commonly used in peripheral and aortic interventions. Video-rate, high-resolution images were obtained during all the interventions tested and provided information that was complementary to simultaneously acquired fluoroscopy. The scanning fiber angioscope was able to detect subintimal dissection and branch vessel stent coverage with higher resolution than fluoroscopy alone.

CONCLUSION

Endoluminal imaging with the scanning fiber angioscope is feasible with current endovascular devices and provides additional relevant information that cannot be assessed fluoroscopically. The scanning fiber angioscope represents a novel optical platform on which new endovascular techniques may be developed that will minimize radiation and contrast doses for patients.

Recent Advances in Fluorescent Angioscopy for Molecular Imaging of Human Atherosclerotic Coronary Plaque

PURPOSE OF REVIEW

In vivo imaging of the native substances, including lipoproteins, that comprise human atherosclerotic plaques is currently beyond the scope of any available imaging techniques. Color and near-infrared fluorescent angioscopy (CFA and NIRFA, respectively) systems have been recently developed for molecular imaging of lipoproteins within the human coronary arterial wall ex vivo and/or in vivo. The author reviews recent findings on lipoprotein deposition in human coronary plaques obtained by these imaging techniques.

RECENT FINDINGS

Using specific biomarkers, native pro-atherogenic substances such as oxidized low-density lipoprotein (ox-LDL), LDL, triglycerides (TG), apolipoprotein B-100 (ApoB-100), and lysophosphatidylcholine (LPC), and the anti-atherogenic substance such as high-density lipoprotein (HDL) were visualized by CFA, and LDL and cholesterol by NIRFA, in coronary plaques obtained from autopsy subjects. The relationship between incidence and plaque morphology differed for each substance. The incidence of ox-LDL and LDL on color fluorescence microscopy correlated well with that observed using immunohistochemical techniques. During coronary catheterization in patients, ox-LDL, LDL, and HDL in coronary plaques were visualized by CFA or NIRFA.

CONCLUSIONS

Using CFA or NIRFA, the distribution of the major native pro-atherogenic and anti-atherogenic lipoproteins and their components within human coronary plaques can be evaluated ex vivo and/or in vivo. Fluorescent angioscopy could help our understanding of the molecular mechanisms of coronary atherosclerosis and in the evaluation of the effects of therapy targeting the substances comprising atherosclerotic coronary plaques.

Fluorescent angioscopic imaging of calcium phosphate tribasic: precursor of hydroxyapatite, the major calcium deposit in human coronary plaques

Coronary calcification is a risk factor for ischemic heart disease. Hydroxyapatite that is formed by polymerization from calcium phosphate tribasic (CPT) is the major constituent of coronary calcium deposits. If CPT could be visualized, coronary calcification could be predicted and prevented. We discovered that when CPT and collagen I, the main constituent of collagen fibers, are mixed with lac dye (LD) and then exposed to fluorescent light excited at 345 ± 15 nm and emitted at 420 nm, a purple fluorescence that is characteristic of CPT only is elicited. So, we examined localization of CPT and its relation to plaque morphology by color fluorescent angioscopy (CFA) or microscopy (CFM) in 24 coronary arteries obtained from 12 autopsy subjects. By CFA, the incidence (%) of CPT as confirmed by purple fluorescence in 15 normal segments, 25 white plaques, 14 yellow plaques without necrotic core (NC) and 8 yellow plaques with NC was 20, 36, 64 and 100 (p < 0.05 vs. normal segments), respectively. By CFM, the CPT was either deposited alone amorphously or surrounded hydroxyapatite that was identified by Oil Red O, methylene blue and von Kossa’s stain. The results suggested that CFA using LD is feasible for imaging CPT, that is a precursor of hydroxyapatite, in human coronary plaques, and this technique would help prediction and discovery of a preventive method of coronary calcification.

Imaging of Triglycerides in Human Coronary Plaques by Color Fluorescent Angioscopy and Microscopy

Native triglycerides (TG) deposited in the human vascular wall is not measurable or visible in vivo to date. We discovered that by exciting fluorescence at 345 nm and emitting at 420 nm, 3-amino-4-hydroxy-5-nitrobenzene sulfonic acid monohydrate (3-ANA) elicits a brown fluorescence that is characteristic of just TG. Therefore, localization of TG in coronary plaques and normal segments that were obtained from 19 human autopsy cases was examined by color fluorescent angioscopy (CFA) and microscopy using 3-ANA as a biomarker of TG. By CFA, the percentage (%) incidence of TG in 23 normal segments, 13 white plaques without lipid deposition, 18 white plaques (growth stage) with lipid deposition, 11 yellow plaques without necrotic core (mature stage), and 12 yellow plaques with necrotic core (advanced mature stage) was 95, 92, 50, 27, and 25, respectively. By color fluorescent microscopy, TG deposited mostly in the fibrotic area of the plaques. Contrary to the general belief that TG amount increases with plaque maturation, the results indicated that TG was deposited in most of the normal coronary segments, but the amount decreased with plaque maturation. If 3-ANA becomes applicable clinically, the CFA system could be used for imaging TG within coronary plaques in patients in vivo.