Abstract
Arteriosclerotic arteries have been shown to fluoresce when treated with hematoporphyrin derivative. This study investigates the incorporation and distribution of a partially purified form of hematoporphyrin derivative (Photofrin II) in normal and arteriosclerotic rabbit aortas. A thoracoabdominal exploration was performed in 15 rabbits. Group I comprised normal rabbits, Group II normal rabbits given 5 mg/kg Photofrin II 48 hours before surgery, Group III arteriosclerotic rabbits and Group IV arteriosclerotic rabbits given 5 mg/kg Photofrin II 48 hours before surgery. Multiple aortic biopsy specimens for frozen section were taken from all rabbits. In addition, open laser endarterectomy (with an argon ion laser) was performed on Group III and Group IV rabbits. Frozen sections were studied by digital video fluorescence microscopy to determine the distribution of Photofrin II within the layers of the aortic wall. The fluorescence of the intima of Group IV rabbits was found to be significantly greater than that of the intima, internal elastic lamina, media or adventitia of the other groups (p less than 0.01) and significantly greater than that of the internal elastic lamina, media or adventitia of Group IV rabbits (p less than 0.01). When open laser endarterectomy was performed, Group III rabbits required 103 +/- 14 J/cm2 and Group IV required 33 +/- 3 J/cm2 (p less than 0.01). It is concluded that porphyrins are selectively localized within the intima of arteriosclerotic arteries. This localization sensitizes atheromas to argon ion laser light and facilitates laser endarterectomy.
Highlights
Arteriosclerotic arteries have been shown to fluoresce when treated with hematoporphyrin derivative
This study investigates the incorporation and distribution of a partially purified form of hematoporphyrin derivative (Photofrin II) in normal and arteriosclerotic rabbit aortas
Three modes of laser-induced thermal destruction of atheromatous plaque have been suggested: I) direct laser light absorption by plaque [1,2,3]; 2) laser heating of a metal cap that is in direct contact with the plaque [4,5]; and 3) a laserheated fiberoptic tip that is in direct contact with the plaque [6,7]
Summary
Arteriosclerotic arteries have been shown to fluoresce when treated with hematoporphyrin derivative. When open laser endarterectomy was performed, Group III rabbits required 103 ± 14 J/cm? It is concluded that porphyrins are selectively localized within the intima of arteriosclerotic arteries This localization sensitizes'atheromas to argon ion laser Iigbt and facilitates laser endarterectomy. If accretion of hematoporphyrin derivative by atherosclerotic plaque is preferential relative to the remaining vessel wall, selective sensitization of the plaque to thermal destruction by an appropriate wavelength of laser light may be possible. This study examines the incorporation and distribution of porphyrins within the wall of atherosclerotic rabbit aortas using digital video fluorescence microscopy [14,15,16] and the photosensitizing properties of certain porphyrins to argon ion laser radiation by open laser endarterectomy [17]
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