[Contribution of excimer laser to coronary angioplasty].
Reports on the problems encountered with thermal laser system in angioplasty have prompted us to test an excimer Xe-Cl laser of 308 nm wavelength and 20 ns impulses on preparations of healthy and atheromatous coronary arteries, the purpose of the study being to quantify the adequate parameters required for angioplasty. We effectively used optic fibres of different diameters--a method which has not yet been reported in medical literature. Our choice of an ultraviolet laser was justified on theoretical grounds: essentially its mode of photo-ablation devoid of thermal effects and proportional to the number of inter- and intramolecular bonds destroyed. The photo-ablation threshold we measured being 1.40 J/cm2, we micrometrically determined the volume of matter removed by various combinations of energy intensities and numbers of impulses, as well as the undesirable effects of such combinations. We found that with an energy surface density of 4.23 J/cm2 the depth of ablation was directly proportional to the number of impulses (between 20 and 100). Under these experimental conditions, the ablation produced by the Xe-Cl laser system was 14 microns per impulse in depth, and of the same diameter as that of the optic fibre used. Virtually identical data were obtained in healthy, fibrotic, atheromatous and calcified tissues. Undesirable effects, i.e. coagulation necrosis, only appeared with high-intensity energies irrelevant to the study. No lesion of the parietal cells was observed, even in the vicinity of the ablation plane. Finally, the question of oncogenic effects raised with 193 nm laser beams does not seem to apply to the 308 nm wavelength.(ABSTRACT TRUNCATED AT 250 WORDS)