Abstract: AIM: To compare the efficacy and safety of low and mid-level linear ablations at Kochs triangle in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT) refractory to conventional slow pathway modification. METHODS: In cases with AVNRT refractory to conventional ablation, elimination of slow pathway, rate of success, time of radiofrequency (RF) delivery and total procedure time were compared between the linear ablations at the low and mid-level of Kochs triangle. RESULTS: No significant difference was seen in the rate of success and the elimination of slow pathway between the groups. However, the time of RF energy delivery at the low level of Kochs triangle was longer than that of mid-level linear lesion ［(578.1±177.4)ms vs.(481.3±185.2)ms, P<0.01］. Moreover, the time needed for the total procedure was shorter by low linear ablation compared with that by mid-level linear ablation ［(152.8±51.2)ms vs.(198.6±56.1)ms, P<0.01］. One patient showed transient one-degree AV block during linear lesion at the mid-level of Kochs triangle and no permanent AV block occurred during the entire procedure. CONCLUSION: Both low and mid-level linear ablations at Kochs triangle are effective and safe in the treatment of the AVNRT refractory to conventional slow pathway modification. However, the procedures of low level linear ablation may be simpler, and mid-level linear ablation could be a backup approach.