Left Atrial Appendage Electrical Isolation (LAAEI)
The LAA is derived from the primordial LA mainly by the adsorption of the primordial PVs and their branches, explaining its role as a potential site of AF triggers. In a non-randomized population of 987 patients undergoing redo AF ablation, 27 % of patients were noted to have triggers arising from the LAA. Moreover, in 8.7 % of the cases, this was the only source of atrial arrhythmia with no PVs or extra-PV reconnection (95).
The RCT BELIEF (Left Atrial Appendage Isolation in Patients with Longstanding Persistent AF Undergoing Catheter Ablation) (96), showed promising results with empiric LAAEI after both index and redo procedures. Among patients who had recurrences and underwent redo ablations, LAAEI was performed in all cases and re-isolated in cases of reconnections. Late LAA reconnections were observed in 37 % of the redo cases. RF and fluoroscopic times were comparable, with no increase in complications. The incremental benefit of LAAEI in addition to PVI was also demonstrated in two meta-analyses including approximately 2000 patients with non-PAF (97,98). This benefit persisted during a 5-year follow-up of 1092 individuals in a propensity score-matched multicenter cohort study. No differences in acute complications or thromboembolic events were evidenced in patients on continued oral anticoagulation (OAC) treatment (99). (Figure 11)
In a propensity score-matched study by Yorgun et al. (100), cryoballoon-based isolation of the PVs and LAA delivered promising results without a significant increase in complications. However, 4 % of the study population had left circumflex artery vasospasm, which resolved with intracoronary nitrate, and 1 % had left phrenic nerve (LPN) injury. It is crucial to prevent mapping and ablation deep into the LAA, as it is a thin structure, and ablation within the lumen is associated with a higher risk of perforation and LPN injury. Imaging integration with cardiac computed tomography and electroanatomic mapping prior to ablation, can help mitigate the potential risk of coronary injury (101). Periprocedural imaging and paced mapping can also delineate the anatomical relationship of the LPN with the LAA, and in case of close proximity a segmental isolation approach should be considered (102).
The thromboembolic risks associated with LAAEI have been a major concern and have shown mixed results. Rillig et al. (103) showed that at a median follow-up of 6 months after LAAEI, 6 % of patients developed stroke or transient ischemic attack, and 21 % were found to have LAA thrombus on transesophageal echocardiogram (TEE). However, all 3 patients had AF recurrence at the time of stroke, and one was off OAC at the time of event. In contrast, no significantly increased risk for thromboembolic events was reported in the LAAEI groups from two meta-analyses, even after a mean follow-up of 40.5 months (97,98). In a large observational study of 1854 consecutive patients with AF receiving LAAEI along with PVI, thromboembolic events were mainly seen in those who had abnormal LAA function. Moreover, patients who were off OAC, receiving subtherapeutic doses, or were non-compliant had thromboembolic complications at higher rates (104). Interestingly, in patients who had normal LAA function on TEE at 6 months, OAC was discontinued irrespective of the CHA2DS2-VASc score, and no thromboembolic events were seen during 2.3 years of follow-up.
For patients in whom long-term OAC is not suitable after LAAEI, LAA occlusion could be considered (105). Another alternative for electrical and mechanical isolation of the LAA is the ligation of the appendage with Lariat, a suture delivery device (SentreHEART, Redwood, CA, USA). This approach has been under investigation, and initially, concerns regarding procedural complications, such as pericardial effusion and the need for urgent cardiac surgery, were reported (106,107). Lakireddy et al. demonstrated improvement in procedural success rate and mortality, while also showing greater freedom from AF recurrence at 1 year follow-up (108). In contrast, the aMAZE (LAA Ligation Adjunctive to PVI for Persistent or Long-standing Persistent Atrial Fibrillation, NCT ) trial failed to demonstrate significant differences in arrhythmia recurrence in patients undergoing left atrial ligation + PVI vs. PVI alone (109).