Radiofrequency catheter ablation was introduced the curative method of supraventricular tachycardia in patients with accessory pathways. The success of catheter ablation depends on the accurate localization of accessory pathway and the destruction of accessory pathways.

We analyzed the local electrograms in 35 patients to be underwent the successful catheter ablation and measured the catheter stability, A/V ratio, AV interval, Accessory pathway potential, and the interval from the onset of RF energy to loss of accessory pathway from local electrograms at the successful ablation sites.

The ratio of A wave and V wave range from 0.06 to 6.33 and the mean of A/V ratio is 0.62. The shortest AoVo interval is 20 msec and the longest AoVo interval is 120 msec and the mean of AoVo interval is 58.23 msec. The shortest ApVp interval is 20 msec and the longest ApVp interval is 100 msec and the mean of this interval is 51.88 msec. The incidence of accessory pathway potential among 35 successful ablation sites in 25%. The mean of time from RF energy to loss of accessory pathway is 4.48 sec.

We concluded that the finding of local electrogram during catheter ablation is very important for shortening of procedure time and the successful procedure.