LAUSR

To the Editor, We have just read an interesting small sized study by Chen et al presenting the efficacy and safety of cryoballoon (CB) based left atrial appendage isolation (LAAi) in patients with persistent atrial fibrillation (PsAF) who have had the history of at least two previous ablation for AF. The authors prefer to apply 240msec bonus freeze in all participants. The durability of LAAi has found as 100% at median 6 months follow‐up which has been assessed during LAA occlusion with 80% atrial tachyarrhythmia free survival at the same time. Although the sample size was small to make any suggestion for clinical practice, it was well‐designed to show the durability of CB for LAAi. We well know that the myocardial sleeves extending from LA onto the pulmonary veins (PVs) were composed of circularly and longitudinally oriented bundles of cardiomyocytes with variable thickness and length. However, the LAA muscular tissue is the continuation of LA tissue rather than an extension and there is thicker tissue around the LA and LAA junction to isolate as compared to antral region. Thus, we thought that we should perform longer duration of CB with a good occlusion grade to create durable lesions. In a previous study, our team also reported that empirical CB based LAAi in addition to PV isolation was both effective and safe method as compared to PVI alone in PsAF. We have observed that there was a high variability in time to LAAi (115.5 [37‐370]msec). Although we have performed cryo‐ application of 450 msec in the first 20 patients, thereafter we changed our protocol according to time‐to‐LAAi and concluded on that if the time‐to‐LAAi was shorter than 150msec, we apply cryoablation for 300msec without bonus freeze and if time‐to‐LAAi was longer than 150msec, we apply bonus freeze of 300msec and also according to our experience, degree of the occlusion grade of LAA and time‐to‐LAAi were much more important than the nadir‐temperature during LAAi. To our knowledge, for the first time in literature, we reported the occurrence of left circumflex artery vasospasm of 4% after LAAi without any symptoms or sign of ischemia in whom high dose intracoronary nitrate administration was required. Therefore, we suggest routine coronary angiography in those patients undergoing LAAi because of close anatomical neighboring. Additionally, in a study Mohanty et al reported that recurrence of AF after previous multiple ablations, non‐PV triggers were shown to be responsible from AF maintenance in the majority and ablation of these triggers enhanced ablation success. furthermore, in the presence of permanent PVI and no non‐PV triggers on isoproterenol, empirical isolation of LAA and CS provided high rate of arrhythmia‐free survival. Thus, the authors may comment on (1) how they decided on the cut‐off time for freezing and bonus freeze; (2) how can we be sure about the absence of coronary vasospasm without invasive imaging? (3) At last, why did the authors prefer to perform cryoballoon based empirical LAAi among patients with the history of at least two ablations before as other non‐PV triggers may also be responsible from tachyarrhythmia?