The optimal values of the AI in the SVCI
Several studies have reported the optimal value of the AI for the PVI and CTI. Although there were minor differences among the studies, the optimal values of the AI for the PVI is 400-500 for the left atrial (LA) anterior wall and 250-400 was for the LA posterior wall (12,13). For the CTI ablation, an AI target of 500 for two-thirds of the anterior segments and 400 for one-third of the posterior segments were needed (14). The optimal value of the AI differed among the ablation sites. In our study, the optimal AI value for the SVCI was 350, and at least 308 would be needed, which was lower than the optimal AI value reported for the PVI and CTI. The wall thickness of the LA differed according to the location and the minimum wall thickness of the LA was 2.2~6.5mm (16). The wall thick ness of the CTI was 2.7~4.1mm (17). However, the wall thickness of the SVC was 1.2±1.0 mm (18). The wall thickness of the SVC was relatively thinner than that of the LA or CTI and that was related to the lower optimal value of the SVCI. Furthermore, pulmonary vein reconnections were frequently observed in higher voltage zones (19). That indicated that higher voltage zones needed higher AI values. Suraj et al. reported the mean bipolar voltage in the LA during sinus rhythm was 1.44±1.27 mV(20). On the other hand, the median bipolar voltage of the SVC in the present study was 0.29 mV (0.16-0.65) and was lower than that of the LA. The the difference in the voltage amplitude between the SVC and PV may have led to the difference in the optimal AI value.