We investigated the implication of clinical use of Nd: YAG Laser delivery onto the atrioventricular groove area for a treatment of WPW syndrome. Eleven mongrel dogs were used in this experiment. After the dissection of the epi-annular fat pad, Nd; YAG Laser was delivered onto the annulus with varing energy levels with the lasing distance kept at 10mm using our new device. A mass of spherical denaturation was formed at the atrioventricular groove area, which would change to a well-demarcated fibrous scar in the chronic phase. When the epi-annular fat pad was completely dissected away, the lower energy lasing even less than 100J made myocardial thinning. The higher energy lasing more than 200J made the trasmural denaturation zone without wall thinning if the lasing to the annulus with the fat pad incompletely dissected and slightly remained should be done.
