By Cara Pellegrini, MD
Assistant Professor of Medicine, University of California, San Francisco, Cardiology Division; Electrophysiology Section, San Francisco VA Medical Center
Dr. Pellegrini reports no financial relationships relevant to this field of study.
SYNOPSIS: Atrial fibrillation ablation leads to better outcomes in heart failure patients compared to amiodarone.
SOURCES: Di Biase L, Mohanty P, Mohanty S, et al. Ablation versus amiodarone for treatment of persistent atrial fibrillation in patients with congestive heart failure and an implanted device. Results from the AATAC Multicenter Randomized Trial. Circulation 2016;133:1637-1644.
Koplan BA, Stevenson WG. Atrial fibrillation in heart failure: Should catheter ablation play a larger role? Circulation 2016;133:1631-1633.
Heart failure (HF) and atrial fibrillation (AF) commonly overlap. With increasing HF severity, the prevalence of AF increases; similarly, more than 40% of AF patients are estimated to also suffer from HF. Causality is likely bidirectional. The loss of atrioventricular synchrony in AF, rapid and variable ventricular rates, and potential toxicity of therapies all may contrive to increase HF burden. On the other hand, those with HF are exposed to high volume and pressure loads, interstitial fibrosis, altered atrial refractory properties, and heterogeneity of conduction, which support development of an AF substrate and triggers. While previous reports have detailed lower success rates of AF ablation in HF patients, small trials have suggested myriad potential benefits of a rhythm control strategy in HF patients, prompting the Di Biase et al study.
Ablation vs Amiodarone for Treatment of Atrial Fibrillation in Patients with Congestive Heart Failure and an Implanted ICD/CRTD (AATAC) is the first randomized trial comparing AF ablation with the most efficacious medical therapy for AF control, amiodarone, in HF patients. More than 200 patients with persistent AF, an implanted device, and HF with a left ventricular ejection fraction (LVEF) of ≤ 40% and New York Heart Association class II-III symptoms were included in the multicenter study. Amiodarone was orally loaded and then dosed at 200 mg daily. AF ablation included pulmonary vein antrum isolation, and in the vast majority, isolation of the posterior wall of the left atrium. A repeat ablation procedure was allowed in the first three months, with follow-up starting only after the second procedure. Freedom from AF, atrial flutter, or atrial tachycardia (mostly) off antiarrhythmic drugs at 24 months was the primary endpoint.
Participants were largely men in their early 60s with less than one year of persistent AF, moderate left atrial enlargement, and mean LVEF of 30%. The ablation group contained a significantly higher number of patients who were recurrence-free at the end of follow-up compared to the amiodarone group (70% vs. 34%, P < 0.001). In addition, the ablation group had significantly lower unplanned hospitalization rates, and greater LVEF, six-minute walk distance, and quality of life improvements. Adverse effects led 10% of amiodarone patients to discontinue the drug prior to the end of the study, while procedural complications were rare (two groin hematomas and one pericardial effusion). Those who underwent ablation had an average of 1.4 procedures. Notably, arrhythmia outcomes differed greatly among included centers, as well as between patients who had pulmonary vein isolation (PVI) alone vs. those who also had posterior wall isolation (36% vs. 79% arrhythmia-free). The authors concluded that catheter ablation is superior to amiodarone for atrial arrhythmia suppression in patients with HF, with several positive secondary effects.
This study is consistent with and extends previous work that has supported a rhythm control strategy, and specifically AF ablation, for patients with HF. Both Catheter Ablation Versus Medical Rate Control for Atrial Fibrillation in Patients with Heart Failure (ARC-HF) and Catheter Ablation Versus Medical Treatment of Atrial Fibrillation in Heart Failure (CAMTAF) have shown better outcomes in terms of exercise capacity and quality of life with AF ablation compared to rate control. Another randomized trial, the Comparison of Pulmonary Vein Isolation Versus AV Nodal Ablation with Biventricular Pacing for Patients with Atrial Fibrillation with Congestive Heart Failure (PABA CHF), found AF ablation also improved cardiac function as compared to the extreme rate control offered by rendering patients pacemaker dependent, even with the benefit of biventricular pacing. This suggests that factors beyond heart rate, such as the loss of atrial contraction and presence of atrioventricular dyssynchrony, may be important in the pathophysiology of HF in AF patients.
The Di Biase et al study has several limitations that are worth mentioning. Patients were relatively well-managed medically prior to ablation, with a high percentage of patients on appropriate medical therapy. They were not the sickest of the sick, with mean LVEF 30% and < 25% with diabetes. Nor were these long-standing persistent AF patients — the mean AF duration was 8.5 months — and their left atria generally were not severely dilated. Generalizability may be further limited by the fact that most patients in the ablation arm had more than the traditional pulmonary vein isolation (PVI) procedure, with no superiority to amiodarone observed among those patients who received PVI alone. While most in the electrophysiology community share the authors’ concern for suboptimal outcomes with PVI in persistent AF patients, results for other techniques frequently are not reproducible among laboratories, and there is a lack of consensus as to which technique is best. Finally, and most notably, the difference between groups was likely exaggerated, given that 12% of patients in the ablation arm were receiving 200 mg of amiodarone daily, and 15% of patients in the amiodarone group were receiving this same “low-dose” amiodarone prior to study initiation, but yet were still in persistent AF, i.e., proven treatment failures.
Data are clearly mounting that HF patients, a group that can prove challenging to treat with AF ablation, may have all the more to gain from it. Happily, in this study ablation success rates were relatively comparable to rates reported in the non-HF population. This occurred in the setting of all patients possessing a cardiac device for the highest level of detection possible for arrhythmia recurrence. The quite low procedural complication rate is also remarkable and reassuring. Providers should think about intervention for AF as early as possible in HF patients, rather than accept its presence as an inevitable companion.