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To establish the method of coronary laser angioplasty using the argon laser, we investigated the optimal condition of laser ablation and the relationship between the size of laser probe and the diameter of the vessel. First, the relationship between laser energy and tissue reaction to the laser was examined using human cadaveric arteries. Subsequently, we recognized that repeated laser ablation is the optimal method with each shot being limited to 5 10 watts (W) in output and 2 seconds of ablation time when using a metal tip probe (MTP) of 1.5 mm in diameter. According to the experimental condition described above, we examined the response of normal coronary arteries to the laser in vivo. If the size of MTP was not suitable for the diameter of the vessel, thermal constriction of the coronary artery was observed; MTP/vessel diameter ratio should be 0.7 or less to avoid vessel constriction by thermal damage from the laser. Neither perforation nor spasm of the coronary artery was found in this experiment. In addition, the ablated area on the coronary artery was healed completely without thrombus formation and coronary stenosis, and it was covered with new endothelium 8 weeks after laser thermal ablation.
Tsuji et al. (Fri,) studied this question.