The 3-month post-atrial fibrillation ablation blanking period: time to redefine?

This editorial refers to ‘Predictive role of early recurrence of atrial fibrillation after cryoballoon ablation’ by G. Stabile et al., on pages 1798--1804. Pulmonary vein isolation (PVI) using various ablation techniques has proven to be an effective treatment of patients with symptomatic paroxysmal and persistent atrial fibrillation (AF). The safety and efficacy of the applied techniques for achieving PVI have improved in the last two decades. However, there are still several clinically important questions to be answered, e.g. the clinical significance of early recurrence of atrial tachycardias (ERATs) within the post-ablation blanking period. This has been investigated in patients treated with 2nd generation Cryoballoon ablation by Stabile et al.1 published in the current issue of Europace. Historically, there has been a variety of definitions of post-ablation blanking period with duration ranging between 3 days up to 3 months and an applied 3-month post-ablation blanking period is the current recommendation by the Heart Rhythm Society, European Heart Rhythm Association, European cardiac Arrhythmia Society, Asia Pacific Heart Rhythm Society, and Latin American Society of Electrophysiology and Cardiac Stimulation.2,3 The occurrence of ERAT has been reported to be as high as 65% depending not only on the applied definition of ERAT but also the method chosen for monitoring and detection of arrhythmias.2 However, there is limited scientific evidence regarding the clinical impact of the ERAT during blanking period, and the underlying mechanisms of the ERAT are not fully understood. Inflammation and modification of the autonomic nervous system caused by the ablation lesion application in the left atrium have been suggested as a plausible explanation for temporary triggering atrial tachyarrhythmias. Hence, ERAT has been suggested to be transient and not associated with treatment failure. Early recurrence of atrial tachycardia following PVI using radiofrequency ablation techniques has been examined in several studies. Among others, in a study by Lee et al.,4 207 patients (155 men; mean age 62 ± 13 years) who received catheter ablation of paroxysmal AF (PAF) were included with a follow-up after 2 weeks and then every 1–3 months up to mean follow-up of 30 months. A 24-h Holter monitoring or cardiac event recording was performed in patients with symptoms suggestive of tachycardia. Early recurrence of AF was defined as AF occurring within 1 month after ablation. Eighty-one (39%) patients had early recurrence of AF. However, late recurrence of AF was observed in only 43% (n = 35) of the patients who had an early recurrence. Hence, more than half of patients with ERAT had a delayed cure during follow-up. However, the incidence and the predictive role of ERAT after Cryoballoon ablation are sparsely investigated. Mugnai et al.5 studied 331 consecutive patients with drug-resistant PAF who underwent PVI using Cryoballoon technology. The follow-up period was 12 months with scheduled Holter monitoring at 1, 3, 6, and 12 months. External loop recorders (minimum 1 week), trans-telephonic monitors, or interrogation of implanted devises were used in patients with symptoms outside the planned monitoring. Atrial tachycardia or AF was detected in 57 (17.2%) of the patients. Of these, 29 during the blanking period (3 months) with the highest prevalence within the first 2 weeks. Nine out of the 29 patients with ERAT had no further relapse after the blanking period. All patients with ERAT during the last 1.5 months of the blanking period were affected by late recurrence of AF. They concluded that ERAT is strongly associated with relapse of AF after PVI using 2nd generation Cryoballoon technology. The new study by Stabile et al. in the current issue of Europace examines the same question in a larger multicentre design. The study is a retrospective registry study based on data from 47 Italian cardiology centres. Patients aged 18–90 (n = 3681) with documented symptomatic PAF or persistent AF, refractory to antiarrhythmic therapy were included. Ablation was performed using 2nd generation Cryoballoon (Arctic Front Advance, Medtronic) technique. Neither the number nor the duration of freeze cycles or usage of bonus freezes were protocolized. Patients were scheduled for follow-up at 3, 6, and 12 months post-ablation and every 6 months afterwards. The main follow-up was 16.8 ± 16.4 months. Documented AF recurrence was seen in 25% (n = 923/3681) of the patients during the follow-up period and 8.6% (n = 316/3681) of the patients had ERAT which mainly represented AF (n = 305). Rhythm monitoring after the procedure was not protocolized in this study. Implantable cardiac monitor was used in 10.1% of the patients and Holter monitoring was performed in 56.4%, 55.3%, and 48.5% of the patients at 6, 12-, and 24-month follow-up. The unadjusted freedom from AF at 12-month follow-up was significantly lower in patients with ERAT compared to patients without ERAT both in patients with PAF (43% vs. 81.4%, P < 0.001) and persistent AF (30.7% vs. 73%, P < 0.001). Similar finding was seen when adjusting the analysis by using propensity score matching at 24-month follow-up. The logistic model analysis showed that ERAT during the complete 3-month blanking period but also a shorter period of only 1-month post-ablation both were strong predictors of later AF recurrence. Hence, Stabile et al. conclude that early recurrence of AF is a strong predictor of AF recurrence when they occur more than 30 days after the ablation. The strength of the study is that it is a multicenter study and includes a much larger patient cohort than the previous studies examining the predictive role of ERAT in patients treated with Cryoballoon technology. However, there are some issues to consider in the interpretation of the study. It is stated that the antiarrhythmic drugs (AADs) were discontinued ≥5 half-lives prior to ablation, except for amiodarone. Still 905 (24.6%) of the patients were on AAD drug during the blanking period (n = 98/316 of patients with ERAT). Whether there was a difference in the used AAD between the two groups is not reported. Early recurrence of atrial tachycardia was documented using different methods. Implantable cardiac monitor was used in 10%, whereas 50% had multiple Holters. Also, the duration of the monitoring is not reported. Hence, there is a considerable risk of underestimating the occurrences of asymptomatic tachycardias during the follow-up period. In conclusion, the current study by Stabile et al. once again questions the duration of the applied 3-month post-ablation blanking period before evaluating the effect of PVI using Cryoballoon technique. Do we now have enough data to support the blanking period be shortened to 2 months or even 1 month? In our opinion, we are not there yet. We could learn more by analysing data from the recent and future emerging study cohorts using Insertable Loop recorder for post-ablation arrhythmia follow-up with various ablation techniques. Furthermore, the safety of a generic shorter blanking period needs to be investigated in controlled trials to ensure that we do not inflict unintended complications in the patients by doing sequential ablation in the left atrium within a short time period. Conflict of interest: none declared. The opinions expressed in this article are not necessarily those of the Editors of Europace or of the European Society of Cardiology.