Linear ablation for AF
Multiple previous studies have reported that linear ablation for PsAF is associated with favorable medium term outcomes, with success rates of 69-88% at 1-1.5 year after CA.6,18,19 Gaita et al. reported that PVI plus linear ablation is superior to PVI alone in maintaining SR during a maximum follow-up period of 3 years.20 while the superiority of linear ablation have not been consistently demonstrated compared with PVI alone.9,10,21 The concept of linear ablation was derived from the evidence of high success rate of the surgical MAZE procedure.22 Roof and MI lines have a potential benefit for alteration of AF wavelet propagation and elimination of spectral components by complete bidirectional block of linear lesions. In addition, these linear lesions lead to reduction of excitable LA myocardial mass, the attenuation of vagal innervation23 and elimination of non-PV foci, especially relating to the ligament of Marshall.24,25Although the endpoint of linear ablation is clear, establishing linear block, especially during MI line ablation, maybe challenging. Incomplete linear ablation has been associated with the occurrence of macro-reentrant AT,26,27 and AF recurrences.28,29 In the present study, although acute success rates of linear ablation were relatively high (94% in roof line, 81% in MI line), roof and MI lines were reconnected in 38% and 54% of patients at re-do procedures. Nevertheless, the incidence of linear gap-related AT was observed in only 13%, which was statistically similar with EGM-guided ablation group. These results may suggest that complete linear block is important for the modification of AF substrate, rather than for avoiding occurrence of macro-reentrant AT. It was possible to create durable linear lesions by using steerable sheaths in our study compared with other previous studies, which may have led to a better clinical outcomes.