The healing of contact Nd:YAG laser irradiated arterial wall. An experimental study in piglets.

The healing of an arterial lesion created by continuous wave contact Nd:YAG laser was investigated. Normal arterial walls were irradiated. It is nearly impossible to irradiate atheromatous plaques without involving adjacent normal arterial wall as well. The purpose of this study was to evaluate the healing process using a standard thermal laser. Different power outputs were used with 1.0 sec exposure. A cw Nd:YAG laser with a wavelength of 1064 nm was used. Eighteen piglets underwent laparotomy. An 0.6 mm fibre with a rounded 2.2 mm sapphire probe was introduced into the aorta and iliac arteries. The irradiation was performed vertically to the vessel wall. The artery specimens were studied histologically and through electron scanning microscopy. Immediately after irradiation, adherence of platelets was observed. At two days the core centre was invaded with mononuclear blood cells and polymorphonuclear leukocytes. At five days there was still some denudation of endothelium, and the initial debris started to disappear. At two weeks medial smooth muscle cells were seen around the necrotic zone. The area was encapsulated by layers of smooth muscle and collagen. The healing process seems similar to that of mechanical injury of the aortic intima.