In Vivo human atherosclerotic plaque recognition by laser-excited fluorescence spectroscopy

Arterial wall perforation and chronic restenosis represent important factors limiting the clinical application of laser angioplasty. Discrimination of normal and atherosclerotic vessels by laserexcited fluorescence spectroscopy may offer a means of targeting plaque ablation, thereby reducing the frequency of restenosis and transmural perforation. In this study, with use of a 325 nm low power helium-cadmium laser, in vivo endogenous surface fluorescence was excited through a flexible 200 μm optical fiber within a 0.018 in. (0.046 cm) guide wire in contact with the intima of 268 vascular interrogation sites from 48 patients either during open heart surgery or during percutaneous catheterization procedures. Fluorescence spectra could be recorded in all patients in bloodless and blood-filled arteries. Endogenous surface fluorescence was analyzed measuring peak intensity, peak position and shape index of the spectra. Compared with normal wall, noncalcified and calcified coronary atheroma showed a 42% (p <0.001) and a 58% (p <0.001) decrease of peak intensity, and higher shape index (p <0.001 and p <0.01, respectively). In addition, peak position was shifted to longer wavelengths for noncalcified coronary atheroma (p <0.001). Compared with normal aorta sites, aortic plaques demonstrated a 46% decrease of peak intensity, longer peak position wavelengths (p <0.05) and a higher shape index (p <0.001). Using an atheroma detection algorithm, prospective analysis of aorta and coronary spectra showed a specificity of 100% for identifying normal sites and a sensitivity of 73% for recognizing atherosclerotic sites. This study demonstrates that in vivo laser-excited fluorescence spectroscopy of remote human arteries with optical fibers, in either a bloodless or a blood-filled environment, is feasible and accurately discriminates, with use of a real-time computercontrolled algorithm, atherosclerotic from normal vascular tissue. Thus, incorporation of fluorescence spectroscopic feedback control in a laser angioplasty system is feasible and may improve clincal results.