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)