Angiographic contrast media interference with laser-induced fluorescence excitation and detection in atherosclerotic human coronary arteries

Optical detection of triggered atherosclerotic plaque disruption by fluorescence emission analysis

Fluorescence emission analysis (FEA) has proven to be very sensitive for the detection of elastin, collagen and lipids, which are recognized as the major sources of autofluorescence in vascular tissues. FEA has also been reported to detect venous thromboemboli. In this paper we have tested the hypothesis that FEA can reproducibly detect in vivo and in vitro triggered plaque disruption and thrombosis in a rabbit model. Fluorescence emission (FE) spectra, recorded in vivo, detected Russell's viper venom (RVV)-induced transformation of atherosclerotic plaque. FE intensity at 410-490 nm 4 weeks after angioplasty was significantly lower (P < 0.0033 by analysis of variance) in RVV-treated rabbits when compared to control animals with stable plaque. FE spectral profile analyses also demonstrated a significant change in curve shape as demonstrated by polynomial regression analysis (R2 from 0.980 to 0.997). We have also demonstrated an excellent correlation between changes in FE intensity and the structural characteristics detected at different stages of "unstable atherosclerotic plaque" development using multiple regression analysis (R2 = 0.989). Thus, FEA applied in vivo is a sensitive and highly informative diagnostic technique for detection of triggered atherosclerotic plaque disruption and related structural changes, associated with plaque transformation, in a rabbit model.

Detection of transplant vasculopathy in a rat aortic allograft model by fluorescence spectroscopic optical analysis

BACKGROUND AND OBJECTIVE

Transplant vasculopathy is a leading cause of late cardiac graft loss. We have examined laser-induced fluorescence (LIF) spectroscopy as an optical diagnostic tool for detection of intimal plaque development and inflammatory cellular invasion in a rat model of aortic allograft transplant.

STUDY DESIGN/MATERIALS AND METHODS

Infrarenal aortic segments were transplanted from Lewis to Sprague Dawley rats. A range of vasculopathy development was produced by treatment with a viral anti-inflammatory protein. LIF spectra were recorded from the intima of aortic implants at 28 days. Fluorescence intensity was analyzed for correlation with vasculopathy development.

RESULTS

Significant differences in LIF intensity at 400-450 nm (P < or = 0.05 by ANOVA) were detected. LIF emission was correlated with plaque growth (R2 = 0.980), vessel narrowing (R2 = 0.964), and cellular invasion (R2 = 0.971) by regression analysis.

CONCLUSION

LIF optical analysis provides a nontraumatic diagnostic approach for detection of atherosclerosis prior to cardiac transplant or during development of vasculopathy after transplant.

Single-laser approach for fluorescence guidance of excimer laser angioplasty at 308 nm: evaluation in vitro and during coronary angioplasty

BACKGROUND AND OBJECTIVE

Spectroscopic guidance of laser angioplasty has been attempted using a diagnostic He-Cd laser in addition to the therapeutic laser system. This study evaluated a single-laser approach for simultaneous ablation and fluorescence excitation.

STUDY DESIGN/MATERIALS AND METHODS

A spectroscopy system was coupled to a clinical XeCl excimer laser. Ablation of 162 human aortic samples in saline and blood with 45 mJ/mm2 per pulse yielded 676 fluorescence spectra validated histologically. The same equipment was used in 16 patients for angioplasty of 18 coronary stenoses applying 500 to 1,725 pulses with 45 to 60 mJ/mm2 under saline flushing. A total of 783 spectra were recorded and validated by intracoronary ultrasound (categories: atheroma, fibrous plaque, calcified lesion).

RESULTS

In vitro, 5 types of spectra could be differentiated: (1) atheroma, (2) fibrous plaque, (3) calcified lesion in saline, (4) media, and (5) calcified lesion in blood. Discriminant analysis prospectively classified 576 validation spectra with the following sensitivity and specificity for each type: (1) 83.5 and 97.1%, (2) 85.7 and 96.8% (3) 100 and 98.5%, (4) 98.1 and 99.3%, (5) 98.9 and 100%, respectively. In vivo type 1, 2, 3, and 5 spectra were also observed, but not the media spectrum. The predominant sonographic category also prevailed in spectroscopy. Calcified lesions yielded type 3 and 5 as well as mixed spectra.

CONCLUSIONS

Using an excimer laser for angioplasty allows combining ablation and fluorescence excitation without a diagnostic laser. Principal types of atherosclerotic lesions and the media can be differentiated spectroscopically with this approach.

Laser-induced fluorescence: III. Quantitative analysis of atherosclerotic plaque content

BACKGROUND AND OBJECTIVE

Laser-induced fluorescence (LF) spectroscopic analysis of the chemical composition of atherosclerotic plaque was examined.

STUDY DESIGN/MATERIALS AND METHODS

The intima of 18 dog aortas was injected with chemical compounds found in atherosclerotic plaque. Spectra were recorded in air prior to and after injection of collagens I, III and IV, elastin, cholesterol, triglyceride, and beta-nicotinamide adenine dinucleotide (NADH).

RESULTS

Significant changes in LF intensity were detected after injection of collagens I and III, cholesterol and elastin in thoracic aorta (P < 0.001), but not with triglyceride or NADH. Minor changes were detected in abdominal aorta. Multiple regression analysis of LF intensity ratios demonstrated a clear correlation with the quantity of injected collagens I (R2 = 0.90-0.99) and III (R2 = 0.84-1.0), cholesterol (R2 = 0.72-0.76), and triglyceride (R2 = 0.68-0.80) in both thoracic and abdominal aorta. The correlation between LF and atherosclerotic plaque composition was confirmed in a rooster model of atherosclerosis where multiple regression analysis predicted the measured aortic cholesterol (R2 = 0.78) and triglyceride content (R2 = 0.96).

CONCLUSIONS

(1) Fluorescence spectra recorded from dog aorta were significantly altered by injection of collagens I and III, cholesterol, and elastin. (2) LF may allow quantitative assessment of plaque chemical content.