Atrial fibrillation ablation long-term outcomes: is there light at the end of the tunnel?

This editorial refers to ‘Very long-term outcome following transcatheter ablation of atrial fibrillation. Are results maintained after 10 years of follow-up?’ by F. Gaita et al., 20(3); 443–450. Since the introduction of catheter ablation as a mainstream treatment for atrial fibrillation (AF) by Haisaguerre et al.,1 several iterations on technique and definitions of a successful procedure have been put forward. The naiveté of electrophysiologists claiming that a catheter-based procedure could ‘cure’ AF was most likely spurred by our enormous and uncontestable success eliminating accessory pathways and atrioventricular (node) re-entrant tachycardias. Soon enough evidence accumulated proving otherwise. First, we do not ‘cure’ AF. Secondly, most patients undergoing AF ablation will require multiple procedures. Finally, we still need to prove that AF ablation reduces stroke, heart failure, death, and other clinically important outcomes such as hospital admissions, electrical cardioversion, and overall health resource utilization. Nonetheless, some glimmer of light can be seen at the end of the tunnel. In this issue of EP-Europace, Gaita et al.2 provide 10-year follow-up data on AF patients that underwent catheter ablation at a single centre, including success rates, quality of life, and predictors of AF recurrence. This observational study included 255 consecutive patients that were mostly male, half had paroxysmal AF, who underwent ablation between June 2004 and June 2006. Patients with hypertrophic cardiomyopathy and moderate to severe valve disease were excluded. Patients were followed for 10 years at biannual visits after the first year and included collecting patient demographic and clinical characteristics, routine laboratory measurements, and 24-h Holter electrocardiogram recordings. No patients were lost to follow-up except those that died. Predictors of recurrence included a greater left atrial diameter. In contrast, no increase in blood pressure [hazard ratio (HR), 0.06)], fasting blood sugar (HR, 0.58), and body mass index (HR, 0.06) during follow-up seemed to be protective against AF recurrence. Quality of life improved significantly in those without the arrhythmia recurrence, reduced arrhythmia burden, and control of cardiovascular risk factors. The current study adds to our knowledge on the natural history post AF ablation by extending follow-up by a decade. Previous studies have reported follow-up for up to 5 years and provide comparable success rates.3,4 Ablation success rates are clearly dependent on the type of AF and it is known that outcomes are not as enticing in patients with persistent AF and long-standing persistent AF. The ablation approach used by the authors for paroxysmal AF patients consisted of pulmonary vein isolation (PVI). Persistent and long-standing persistent AF patients, in addition to PVI, also included ablation with lines at the roof, mitral isthmus, and/or complex fractionated electrogram ablation. It is still unclear whether a strategy including more ablation lesions is better in persistent AF, and recently the Substrate and Trigger Ablation for Reduction of Atrial Fibrillation (STAR AF II) trial did not show any added benefit to PVI when either further ablation lines or complex electrogram targeted ablation were done.5 Most electrophysiologists include either during the first and most likely during repeated procedures the addition of a variety of lines and non-pulmonary vein targets that include rotors, fractionated electrograms, and other triggers when approaching patients with persistent AF. However, long-term outcome of the PVI only approach in persistent AF is not known. What was the ‘success’ rate in this long-term follow-up cohort? The authors report that at 10-year follow up 52% were arrhythmia free. A single procedure had only a 32% (39% in paroxysmal and 24% in persistent) success rate. More than one procedure was needed in the vast majority and improved success rate to 61% in paroxysmal and 44% in persistent AF. Progression to persistent AF was only about 1% per year suggesting that these patients possibly did not have severe atrial remodelling. What burden of AF triggered the authors to proceed to a second or 3rd procedure is unclear. By-in-large recurrences were defined mostly by symptoms with some evidence from ECG or Holter documented AF. It is likely that both asymptomatic and symptomatic AF episodes may have been undetected, overestimating the reported success rate. Nonetheless, the current success rates are in keeping with 5-year follow-up reported success rates3,4. Finally, ablation technology used is outdated and may have influenced success rates. From the patient’s perspective one of the main goals after an AF ablation is to reduce or discontinue the use of antiarrhythmic drugs (AAD) and reduce hospital admissions. Overall 66% of patients were AAD free and recurrences of AF were documented in about one-third. When stratified recurrences by use or not of AAD a weak trend emerged towards a lower prescription of drugs in patients not experiencing recurrences. Hence it was suggested that long-term AADs can be stopped in patients not experiencing recurrences. However, it is not clear whether the patients were not having recurrences because of AAD use and why the physicians chose to carry on with AADs for many years in these patients without recurrences. This study reiterates our knowledge that an increased left atrial size predicts recurrence of AF post-ablation. Nonetheless, we still struggle to deny ablation based exclusively on this criterion. Of note in this series cardiovascular risk factor control, specifically blood pressure, fasting glucose, and body mass index had significant impact on the long-term sustainability of AF Ablation. These findings are in keeping with other studies that have identified similar risk factors as important markers of ablation success5, and should encourage electrophysiologists to manage their patients within a multidisciplinary perspective as recently proposed by the European Society of Cardiology Guidelines on AF.6 The AF ablation population has not been extensively studied for cardiovascular risk factors, but studies such as the Aggressive Risk Factor Reduction Study for Atrial Fibrillation (ARREST-AF), have found that risk factor management can result in improved long-term outcomes after ablation.7 Management of other metabolic risk factors such as dyslipidaemia, alcohol, smoking, and sleep apnoea may also be beneficial in maintaining sinus rhythm after ablation.8 Therefore, it is reassuring that the current study supports the importance of control and modification of risk factors resulting in less recurrences of AF. Does AF ablation reduce important clinical outcomes such as stroke and death? Nine patients experienced thromboembolic events; 8 were during recurrences of AF of which 3 were not on anticoagulation. Based on this, the authors have estimated an incidence 0.02 per 100 patient years compared to the 1.3–2.2 per 100 patient years predicted on a CHAD2DS2-VASc score of 1.5. It is tempting to speculate that ablation may have reduced thromboembolic events, but this is a very small sample with a low event rate. However, Saliba et al.,9 in propensity matched analysis, have recently reported an incidence rate of stroke or transient ischaemic attack of 2.10 and 3.26 per 100 person-years in the ablation group and the non-ablation group, respectively, (crude HR, 0.58; or 42% relative risk reduction), highly suggestive of the beneficial effect in favour of ablation.9 However, similarly to larger post-ablation studies, in patients who are closely monitored after ablation, off AADs, and have no recurrences, it may be reasonable to stop anticoagulation, and patients with successful ablation seem to have much lower stroke risk than predicted by risk scores such as CHAD2DS2-VASc.10 Whether oral anticoagulation may be discontinued post ablations remains to be tested in properly designed trials. Death was reported in 20 (7.8%) of the patients during follow-up and none due to the ablation directly. This is higher than expected using a Framingham risk approximation. Given that patients had the average age at inclusion 58 years and had preserved ejection fraction and minimal dyslipidaemia and diabetes, with only half having hypertension and only 11% with structural heart disease, a lower mortality may have been expected. The mortality reported from 5-year follow-up AF ablation studies with a slightly higher risk population were in the range of 0–2%.3,4 The nature for this discrepancy is unclear but begs follow-up of larger datasets. The current study adds to our knowledge by providing long-term (10 years) follow-up and highlights that in patients that do not present with significant atrial remodelling, AF ablation is an acceptable therapeutic strategy. The goal of ‘curing’ AF is unattainable but we can significantly improve symptoms and potentially modify thromboembolic risk and hopefully and ultimately mortality. This study highlights the importance of convincing the electrophysiologists performing AF ablations to take a multidisciplinary perspective and promote overall risk factor reduction and control that in turn will potentially improve real hard outcomes, reduce health resource utilization and finally turn that ‘glimmer at the end of the tunnel into a clear bright light’. The burden is on us to continue providing evidence to prove us right!

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