What happens during the blanking period does not stay in the blanking period

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Excerpt

Catheter ablation is increasingly used to treat symptomatic, drug‐refractory atrial fibrillation (AF). Within the first 3 months after ablation, early recurrences of AF and atrial tachycardia (AT) are common and felt to have uncertain, long‐term significance. Thought to be due to the inflammatory response from ablation, these recurrences have long been regarded as nonspecific without need for further intervention. This 3‐month, periprocedural “blanking period” is recommended by the Expert Consensus Statement on Catheter and Surgical Ablation of AF when determining procedural efficacy. In the absence of symptoms, routine monitoring is not recommended during this timeframe.1 This recommendation has not only been adopted into routine clinical practice, but is also a standard feature of clinical trial design. Increasingly, reports have called into question the length of the blanking period2 and called attention to the potential prognostic significance of recurrences during this timeframe.3 It is also important to recognize the negative impact that recurrent AF and AT often have on the patient's experience with ablation and the need to capture these outcomes in clinical trials.
Immediate recurrences after ablation are likely due to the acute inflammatory response caused by myocardial tissue damage from ablation. Inflammatory markers, however, appear only to be significantly increased for only the first week after the procedure5 and are an unlikely explanation for all recurrences in the first 3 months. Tissue edema appears to resolve within 4 weeks in both animal models and humans.6 In addition, many reports indicate that the most likely timeframe to develop early recurrences is the first 2 weeks after ablation with a progressive decrease in incidence thereafter.2 There appears to be an inverse relationship between the time to early recurrence and late‐term atrial tachyarrhythmia outcomes. Patients with a recurrence >1 month postablation fare much worse than those with recurrences within the first month.4
In this issue of JCE, Pieragnoli et al. add to this evolving literature by reporting their experience with recurrences during the blanking period after cryoballoon ablation for AF.11 They followed a small patient population of both paroxysmal and nonparoxysmal AF patients. With implantable loop recorders (ILRs), they reported the rates of early and late AF recurrence as well as the prognostic value of early recurrences. They report that >80% of patients with early recurrence went on to develop late recurrences, a likelihood ratio of 5.7. In a multivariate analysis, the presence of nonparoxysmal AF and early recurrence were independent predictors of late recurrence.
The authors should be commended on their contribution as it has both confirmed other reports but also served as an important addition to this literature. Most of the previous research in this area, especially in patients with ILRs, has focused on radiofrequency (RF) ablation rather than cryoballoon ablation. Lesion formation and inflammatory response are different between the 2 technologies and the method of recurrence may be as well. The use of ILRs in this study allowed for accurate and continuous arrhythmia detection, even if the patients were asymptomatic.
These data, in aggregate, argue against the use of an extended (3 months) blanking period after AF ablation with the potential to decrease this period to as little as 1 month. The utility and timing of reintervention in the presence of early recurrence remains unclear and warrants further study. In addition, these findings beg the question as to whether large AF trials should continue to ignore the blanking period when reporting outcomes, as is the current standard practice. For example, the FIRE and ICE Trial12 ignored events during the 90‐day blanking period and reported that the primary endpoints were found to be similar between cryoballoon ablation and RF ablation for AF.
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