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Review Atrial Fibrillation The Blanking Period Following Pulmonary Vein Isolation – Relevance and Duration Moloy Das 1 and Dhiraj Gupta 2 1. Freeman Hospital, Newcastle upon Tyne, UK; 2. Liverpool Heart and Chest Hospital, Liverpool, UK Abstract Early recurrences of atrial tachyarrhythmia (ERAT) commonly occur in the initial months following catheter ablation of atrial fibrillation. Patients with ERAT are at increased risk of later recurrence, but the presence of ERAT does not necessarily indicate longer-term procedural failure. International consensus guidelines accordingly recommend a three-month ‘blanking period’. Such ERAT episodes may be related to post-ablation pro-arrhythmic factors, such as inflammation, autonomic dysregulation and lesion maturation. However, studies suggest that these transient factors have a limited duration and ERAT occurring beyond this point may be more predictive of both pulmonary vein reconnection and further recurrence. This review examines the need for a blanking period and its most appropriate duration. Keywords Atrial fibrillation, catheter ablation, pulmonary vein isolation, blanking period, AF recurrence Disclosure: Dhiraj Gupta has received speaker fees, research grants and Fellowship support from Biosense Webster, Inc. Moloy Das has nothing to declare in relation to this article. No funding was received in the publication of this article. Open Access: This article is published under the Creative Commons Attribution Noncommercial License, which permits any noncommercial use, distribution, adaptation, and reproduction provided the original author(s) and source are given appropriate credit. Received: 27 January 2016 Accepted: 18 April 2016 Citation: European Journal of Arrhythmia & Electrophysiology, 2016;2(1):26–9 Correspondence: Dhiraj Gupta, Department of Cardiology, Liverpool Heart and Chest Hospital, Thomas Drive, Liverpool, L14 3PE, UK. E: dhiraj.gupta@lhch.nhs.uk Catheter ablation has been consistently shown to provide improved freedom from atrial fibrillation (AF) compared to medical management but, nevertheless, success rates following a single procedure remain relatively poor and are significantly lower than those for ablation procedures for most other supraventricular arrhythmias. 1,2 Recurrence of atrial tachyarrhythmias (AT; comprising AF, atrial flutter or atrial tachycardia), either symptomatic or asymptomatic, has been reported to occur in more than one in two patients in long-term follow-up after ablation. 3,4 Outcomes for paroxysmal AF are better than for persistent AF, 5 and although success rates have gradually increased as procedural techniques have evolved, even in contemporary studies of paroxysmal AF patients ablated using radiofrequency energy, freedom from AF at 1-year follow-up after a single procedure has only approached 70%. 6 These disappointing success rates may contribute towards the difficulty in establishing clear prognostic benefits, such as stroke-reduction, of catheter ablation over medical therapy. Recurrence of AT can occur at any time following catheter ablation of AF. While the majority occur in the first 6 months after ablation, first recurrences have been seen more than 4 years later. 4 AT recurrence in the immediate aftermath of left atrial ablation is particularly common, 7–9 and the frequency and extent of episodes can exceed those experienced prior to ablation in around 15% of patients. 10 However, there remains some debate over the true relevance of such recurrences in the immediate period following AF ablation. Early recurrence of atrial tachyarrhythmia It has long been recognised that early recurrences of AT (ERAT) occurring soon after radiofrequency ablation may not necessarily 26 portend longer-term arrhythmia recurrence, 10,11 with up to 60% of patients experiencing ERAT going on to have a successful outcome in the longer-term. 12 Accordingly, international consensus guidelines recommend a 3-month ‘blanking period’ following AF ablation during which AT recurrences “should not be classified as treatment failure”. 12 However, data have also shown that individuals with ERAT have lower long-term success rates than those without early recurrence, 7,13–16 and that patients with ERAT who undergo early re-ablation have improved freedom from AT at 12 months, 17,18 suggesting that ERAT may be of clinical relevance. The mechanisms leading to ERAT following radiofrequency ablation are not fully understood but are commonly attributed to a number of transient pro-arrhythmic factors. These include: post-ablation inflammation, 19,20 temporary autonomic imbalance 21,22 or the time taken for the lesion set deployed to mature. 23 Whilst pulmonary vein (PV) reconnection has been shown to be associated with long-term arrhythmia recurrence in paroxysmal AF, 24–26 these transient factors would not be expected to lead to late AT recurrence. However, the time point at which these transient causes of ERAT give way to arrhythmia episodes related to PV reconnection has not been clearly established. Post-ablation inflammation Inflammation has been identified as an important cause for the initiation and maintenance of AF, including after major inflammatory insults such as cardiac surgery. 20,27 Radiofrequency catheter ablation of cardiac tissue also stimulates a strong inflammatory response, with histological examination demonstrating infiltration of inflammatory cells into the ablated area and measurement of serum markers of inflammation TOU C H ME D ICA L ME D IA