[Effects of different types of continuous emission laser on human atheromatous plaques in vitro]

The laser beam is a punctual source of thermal energy which can be used to vaporize human atheroma. The physical characteristics of optimal utilisation (total energy, wave length, continuous or pulsed emission) have not been clearly defined. We carried out in vitro irradiations of human atheromatous material and healthy arterial wall with different combinations of power-emission time and three different wave lengths, using four continuous emission laser beams (Nd-Yag, two CO2 with different lenses, Argon). The beam emitted by the Nd-Yag was absorbed less than the CO2 and Argon lasers, which had comparable effects above a threshold of 2 to 14 joules. The weight of vaporized fibro-atheromatous material was 0.11 mg per joule of optical energy dissipated (CO2). No radical difference was observed in the nature of the effects of the three types of laser studied. The problems of using this technique on the beating heart remain unsolved (ballistics of the emerging ray). Other modes of emission (pulsed) and different wave lengths should be studied.