Laser-induced fluorescence identification of intimal hyperplasia after intravascular stent implantation

Laser-induced fluorescence spectroscopy has been developed as a guidance system for laser angioplasty. We have investigated fluorescence spectroscopic detection of neo-intimal formation from the endoluminal surface of stent implanted arteries. Nine White Leghorn roosters had Palmaz-Schatz intra-abdominal aortic stent implantation, nine had aortic balloon angioplasty. Five roosters with stent implantation and four roosters with balloon angioplasty were on a high cholesterol diet and the remainder were on a normal diet. Roosters were sacrificed at intervals of 1, 2, 4, 8, and 12 weeks after intervention. Fluorescence emission spectra were recorded from aortic segments during excimer laser excitation at 308 nm (XeCl, 1.5 - 2.0 mJ/pulse, 5 Hertz). Spectra were then correlated with histology. Fluorescence emission intensity recorded from abdominal aortic segments with stent implantation was higher than that of adjacent segments (p < 0.002 at 440 - 460 nm). Abdominal aortic segments of roosters on normal diets with stent implantation and balloon angioplasty were similar (p = NS). With cholesterol feeding, aortic spectra from roosters with stent implant had higher intensity at 440 - 460 nm than spectra from aortic segments with balloon angioplasty (p < 0.004). Morphometric analysis demonstrated a twofold increase in intimal thickness in stent segments from cholesterol fed roosters when compared to similar segments of roosters on normal diets (p < 0.005). Our conclusion is: (1) Fluorescence emission spectra can be used to detect native artery fluorescence in stent implant areas. (2) Neo-intimal thickening at the stet implant site can be distinguished from adjacent areas by fluorescence emission spectra. (3) Cholesterol feeding increased neo-intimal thickening.