CO laser may be effective for thermal fusion of intima of arterial wall without adventitial tissue damage because of high tissue absorption. To investigate the efficacy of CO laser as laser beam for laser balloon angio-platy (LBA), CO laser irradiated aortic tissue through 30μ polyethyrene membrane and tissue temperature (TT) was measured by a thermistor. At 20 watt/cm2 200 joules/cm2 continuous laser exposure (CE), TT was above 100°C within a depth of 1mm and rapidly decreased to 60°C or below between 2 and 3mm in depth. Moreover, TT could be decreased by changing duty ratio (exposure duration/interval) of intermittent laser exposure (IE) despite of the same laser energy. Light microscopy showed high degree of medial coagulation necrosis in 200 joules/cm2CE, but thermal coagulation was observed only at the surface of intima of aortic tissue in 200 joules/cm2 IE at duty ratio 1/2. These findings suggested CO laser could coagulate intimal layer with less deep thermal damage compared to Nd-YAG laser and that IE was better for superficial welding than CE at the same energy. We concluded that CO laser might be more efficient as laser beam for LBA than Nd-YAG laser.
