Superior Vena Cava Isolation (SVCI)
The SVC has been recognized as a site responsible for both initiation and perpetuation of AF, and several studies have documented its involvement in PAF and non-PAF (79,80). SVCI is achieved with radiofrequency ablation (RFA), using a segmental approach commencing on the septal aspect of the vascular structure. While ablating the lateral aspect, it is crucial to prevent injury to the phrenic nerve and the sinus node. In up to 10 % of patients, complete isolation of SVC is not feasible, due to the risk of damaging the phrenic nerve. In such patients, ablation of right atrial posterior wall can be employed as an alternative (81). The sinus node lies laterally and below the SVC; RFA should be promptly discontinued if acceleration of the sinus rate is noted (an imminent sign of sinus node injury). It is also imperative to not perform ablation during isoproterenol infusion to avoid masking injury to the sinus node. Cryoballoon has also been used to achieve SVCI and has improved freedom from AT in PAF subjects.(82)
An empirical approach to SVCI has been investigated in a prospective, randomized study (83), which found no significant differences in maintenance of sinus rhythm without antiarrhythmic drugs . The same conclusion was derived from a meta-analysis by Sharma et al. (84)including a total of 526 subjects, in which no difference in AF recurrence when SVCI was added to PVI across all types of AF. When only PAF was analyzed, empiric SVCI showed a trend towards efficacy but failed to reach statistical significance. Yoshiga et al. (85) investigated the incremental benefit of SVCI in recurrent AF after index procedure of PVI without evidence of PVs reconnections on redo procedures and found that SVCI had a success rate of 74 % vs. 66 % in PVI only group. However, SVCI should be attempted with concomitant ablation of other non-PV triggers to obtain better outcomes (86). (Figure 9)