Death after ablation of atrial flutter: are we doing the right thing?

This editorial refers to ‘Death and thrombo-embolic risk after ablation of atrial flutter compared with atrial fibrillation: a nationwide cohort study’ by H. Vadmann et al., doi:10.1093/europace/euw107. Isolated typical right atrial flutter is a relatively uncommon arrhythmia compared with atrial fibrillation (AF) with an incidence of 88 per 100 000 person-years.1 Because of the high symptomatic burden, ablation is usually performed as a first-line therapy with a low complication rate and excellent results.2,3 In addition, long-term survival has been reported to be higher following flutter ablation than in patients with other atrial tachyarrhythmias not undergoing ablation.4 Therefore, operators generally have a low threshold in performing ablation for typical flutter. Interestingly and in contrast to this, Vadmann et al.5 reported in this issue of EP-Europace that mortality was higher after ablation of atrial flutter compared with ablation of AF. They extracted data on all patients undergoing atrial flutter or AF ablation between 2000 and 2013 from the Danish national health registries based on ICD-10 codes and mortality data from the Danish Civil Registration System. During 5 years of follow-up, mortality among 1096 patients who underwent atrial flutter ablation was 3.5%. In contrast, mortality in 2266 patients undergoing ablation of AF was only 1.6%. This difference persisted after multivariate correction for several risk factors. The rate of thrombo-embolic events was, although non-significant, higher in the atrial flutter group. If these very interesting and unexpected results are reproduced in other studies, it may change our strategy in isolated right atrial flutter. The question at hand is: should we perform isolated atrial flutter ablation if this intervention may be associated with increased mortality? The next question that immediately comes to mind is: how often does isolated right atrial flutter occur? It is known that supraventricular arrhythmias and AF frequently coincide. In a retrospective analysis of patients undergoing supraventricular arrhythmia ablation, 27% also exhibited AF, with the highest rate (57%) in the atrial flutter ablation group.6 The presence of AF had a negative impact on survival (76 vs. 84% at 10 years follow-up), although this number was not corrected for the higher co-morbidity rates in patients with concomitant AF. In another study from Pennsylvania, new onset AF occurred in 16% of patients after atrial flutter ablation while 6% suffered from ischaemic stroke. Documentation of AF after flutter ablation was the only significant predictor of stroke.7 A significant number of patients undergoing atrial flutter ablation may also have concomitant but not yet diagnosed AF, which may negatively influence morbidity and mortality. To take things even further, it has been hypothesized that isolated atrial flutter not only coincides with, but might be caused by AF and/or pulmonary vein firing. In the PREVENT-AF study I, patients with isolated atrial flutter were randomized to cavotricuspid isthmus (CTI) ablation only or to CTI ablation combined with pulmonary vein isolation (PVI).8 The study showed that the post-ablation occurrence of AF was reduced from 52 to 12% and AF burden from 8.3 to 4.0%. In the Triple A trial, patients with isolated atrial flutter were randomized to antiarrhythmic drugs, CTI ablation, or PVI.9 Atrial flutter recurrence was 8.7% in the CTI group and 15% in the PVI group. After a second PVI, the rate of atrial flutter dropped to 5% without performing CTI. The authors concluded that pulmonary vein triggers play an important role in the induction of right atrial flutter. In the study by Vadmann et al.,5 the prevalence of AF in the atrial flutter ablation group is unfortunately unknown. This might be due to the nature of studying a national registry based on ICD-10 codes. In the ICD-10 coding system, both AF and atrial flutter are coded with I48, while only subcodes I48.3 and I48.4 are exclusively reserved for atrial flutter. If registration on a subcode level is not required or generally not performed, it may be impossible to differentiate between isolated atrial flutter and atrial flutter with concomitant AF. It is therefore conceivable that the higher mortality observed after atrial flutter ablation is due to a higher prevalence of AF after atrial flutter ablation compared with the prevalence of AF following PVI. One potential explanation for the higher mortality in the flutter group provided by the authors is the higher co-morbidity rate. However, the mortality difference persisted after multivariate correction. In addition, they hypothesized that there might be a less rigorous follow-up after flutter ablation compared with AF ablation. Indeed, the authors found a slightly lower warfarin usage after atrial flutter ablation compared with AF ablation, which might lead to a higher stroke rate and mortality. However, as recurrence of atrial tachyarrhythmias is necessary for persistence of a higher stroke and mortality risk after atrial flutter ablation, this finding further supports the hypothesis that AF after flutter ablation may be the underlying risk factor in the current study. Although this hypothesis needs to be proven in future studies, the consequences may be guideline-changing. If isolated atrial flutter ablation is associated with a high rate of AF during follow-up with increased morbidity and mortality, we may consider adding PVI to an isolated atrial flutter ablation to improve prognosis, regardless of the documentation of AF. Together with other still awaited results from trials on improving prognosis with rhythm control in AF such as the EAST trial,10 this may lead to an important paradigm shift in the prognostic treatment of atrial flutter and AF. Conflict of interest: Serge A. Trines received teaching honoraria from Medtronic AF-Solutions. The Department of Cardiology of the Leiden University Medical Center received unrestricted research grants from Medtronic, Biotronik, Boston Scientific, Lantheus medical imaging, St Jude Medical, Edwards Life sciences, and GE Healthcare.