Left atrial appendage electrical isolation for persistent atrial fibrillation: Radiofrequency vs cryoballoon ablation

We strongly believe that the left atrial appendage (LAA) deserves special consideration when mapping and ablating patients with persistent atrial fibrillation (AF) and long-standing persistent AF (LSPAF). The arrhythmogenic role of the LAA was initially demonstrated in 2010 with a study showing the prevalence of firing from the LAA and the optimal strategy to eliminate these triggers.1 The study not only revealed that 27% of patients had firing from the LAA, but also that in 8.7%, the LAAwas the only source of arrhythmia.1 Complete LAA electrical isolation (LAAEI) showed an arrhythmia recurrence of only 15% at 12-month follow-up.1 The results of the effect of empirical LAAEI on long-term procedure outcome in patients with LSPAF undergoing catheter ablation (CA) (BELIEF study, a randomized controlled trial [RCT]) showed that 28%of patients in the control group and56% in the LAAEI groupwere recurrence free after a single procedure (P=0.001). During repeat procedures, cumulative success at 24-month follow-up was reported in 56% of patients in the control group and in 76% of patients in the LAAEI group (P = 0.003).2 A recent meta-analysis has shown almost a 30% absolute reduction in all atrial arrhythmias recurrence off antiarrhythmic drugs following LAAEI in patients with nonparoxysmal AF without increasing the risk of acute complications or the risk of ischemic stroke at follow-up.3 LAAEI using cryoballoon ablation: Yorgun et al in 2017 sought to evaluate the safety and efficacy of empiric cryoballoon (CB) LAAEI as an adjunct to pulmonary vein (PV) isolation (PVI) compared to the PVIonly strategy. A total of 86% of patients in the PVI + LAAEI group and 67% of patients in the PVI-only group were free of all atrial arrhythmias at 12-month follow-up (P< 0.001).4 In this issue of PACE, Bordignon et al reported their initial experience in LAAEI using the CB and data on durability of CB-LAAEI.5 This was a small, not-controlled retrospective study, in which patients treatedwith aCB-LAAEIwere scheduled for staged percutaneous LAA closure (LAAC) 6 weeks later. During the second procedure, a subset of patients underwent invasive remapping of the LAA.5 One leftsided phrenic nerve palsy occurred. Persistency of LAAEI was tested and durable LAAEI was documented in 73% of cases. These results are novel and clinically relevant due primarily to the fact that the authors have mainly focused on determining the durability of LAAEI with CB.5 The FIRE and ICE RCT determined that CB ablation is noninferior to radiofrequency (RF) ablation (RFA) in patients with paroxysmal AF. Though the feasibility ofCB for non-PV sites is limited, the studies publishedbyYorgunet al4 andnowbyBordignonet al,5 in this issue, clearly demonstrated that this technology might have a larger role in treating patients with nonparoxysmal AF. The authors should be applauded for this outstanding study, particularly for taking the time and use of resources to remap the LAA. Left phrenic nerve (LPN): The LPN typically descends on the fibrous pericardium taking different courses over the LAA: in 59%of the cases, this nerve travels over the distal portion of the posterior wall, and in 23% of patients, over the mid or proximal portion of the posterior wall of the LAA.6 LPN injury can occur and it has been reported during RFA at the proximal roof of the LAA or during CB ablation.7 In the current study, a single LPN injury was noticed (ie, 4%). The function of the LPN in the current studywas controlled through fluoroscopicmonitoring of the left diaphragm contraction. We think a safer maneuver to avoid LPN damage may be to constantly pace the LPN from the left subclavian vein or with the LAA using the circular mapping catheter throughout the freezing cycle. In our experience, we prefer to localize the entire course of this structure in the posterior aspect of the LAA with high-output pacing (20 mA/2 ms) and deliver RF energy at least 5-10mm away from it (Figure 1). Left circumflex artery: No coronary angiogram was done to assess for vasospasm in this study. Yorgun et al performed left coronary angiography simultaneously or after the LAAEI and they observed asymptomatic left circumflex (LCx) artery vasospasm in 4% of the LAAEI group, which was completely resolved after administration of intracoronary nitrates.4 We do not perform routine coronary angiogram after RFA because we have previously localized the left main coronary artery (LMCA) and LCx artery performing imaging integrationwithCARTO-merge andwe have delivered our RF lesions away from these vessels.8 Late LAA reconnections: Although the LAA has a very thin wall, the LAA ostium has a considerablemyocardial thickness. Panikker et al demonstrated in cadaveric hearts that the thickest LAAostial areas are the anterior and superior edges.9 Bordignon et al showed durable CBLAAEI in73%of cases. This value is similar to the late reconnection rate using RFA. Late LAA reconnections were observed in 37% of the redo cases in the BELIEF trial.2 More recently, Reissmann et al reported a 27% reconnection rate after amedian of 3months in redo cases.10 We consider that it is worth assessing for LAA dormant conduction using adenosine or isoproterenol and reassess reconnection after a 30 min waiting period. In this series by Bordignon et al, another great concept arise: LAA occlusion only after confirmation of LAAEI with mapping