Comparative study of different laser systems with special regard to angioplasty

Laser angioplasty has found increasing interest in the treatment of cardiovascular diseases. First clinical applications of laser angioplasty in atherosclerotic stenoses or occlusions of peripheral and coronary vessels primarily showed a high success rate, but later were followed by significant complications as aneurysm formation, late perforations and restenoses. Most of these complications were due to a thermal damage of surrounding wall structures. To avoid these complications an ideal laser system should only minimally influence surrounding tissue layers and should offer a well predictable penetration and ablation including also severely calcified material. In conventional continuous wave laser systems photo energy is mainly changed into thermal energy. Mode of application, local cooling and the use of special laser probes can reduce the thermal side effects, but nevertheless histologic examinations revealed thermal injuries of various degree to surrounding structures. Furthermore these laser systems mostly faile to ablate or penetrate calcified plaques and only pulsed Nd:YAG-lasers with high frequencies seem ot offer some improvement. Eximer lasers with their wave lengths of 193, 248 and 308 nanometers also work in a high frequent pulsed mode. They offer a very low penetration and mainly show a so called photoablative effect with only minimal thermal side effects. Within a distance of only 50 micrometers temperature raises in the surrounding tissue up to 5 degrees C and in a distance of 1 mm, up to 1.5 degrees C. Eximer lasers are moreover able to penetrate calcified material. A transluminal application is up till now limited by a lack of flexible fiber systems, which can deliver the high energy pulses. Another point of discussion are the mutagenity and cancerogenity of ultraviolet light.(ABSTRACT TRUNCATED AT 250 WORDS)