Atrial fibrillation (AF) is a significant factor complicating heart failure (HF). It is estimated that the prevalence of AF is as high as 50% of patients with NYHA class IV. The loss of atrial contribution to ventricular filling, non-physiological fast and irregular heart rate, and increased risk of thrombo-embolism are some of the adverse effects of AF in HF patients.
Whether AF has an impact on survival in chronic HF patients is still a matter of debate. In the recently published AF-CHF trial, no difference was found in cardiovascular mortality between the two treatment strategies. 1 Although antiarrhythmic therapy is currently considered the first-line therapy in AF patients, a recurrence of AF is a common event, with rates as high as 44–67% within 1 year after successful cardioversion. 2 To date, antiarrhythmic drug therapy appears ineffective as a single strategy to maintain sinus rhythm (SR).
Post hoc analyses have demonstrated that patients who remained in SR had better survival rates in both the AF-CHF and AFFIRM trials. 3 There is evidence suggesting that patients with HF and AF have a worse prognosis than patients with HF and SR. 4 The presence of HF has been identified as one of the most powerful independent predictors of AF, with a six-fold increase in relative risk of its development. On the other hand, AF can aggravate, or be the cause of HF in previously asymptomatic or well-compensated patients. Symptomatic dilated cardiomyopathy may develop over time entirely due to AF with irregular and rapid ventricular rates. Upon restoration of SR, this ‘tachycardiomyopathy’ has been shown to be reversible in the majority of the patients. 5 Therefore, the interruption of the vicious circle would be a key point in the treatment strategy of HF patients with AF.
Unlike cardioversion or antiarrhythmic drugs, radiofrequency catheter ablation (RFCA), including pulmonary vein isolation and other left and right atrial ablation targets, offers the possibility of long-term suppressive or curative therapy for AF.
During the initial period of RFCA for AF, left atrial ablation was reserved for highly symptomatic patients without structural heart diseases. With the evolution of AF ablation therapy, including higher success and lower complication rates, the procedural indications were extended to patients with structural heart diseases and HF. However, previously published trials that included patients with reduced ejection fraction demonstrated higher recurrence rates of AF in this population. 6 , 7
De Potter et al.8 report on the outcome of a 1:1 case–control study of RFCA in 72 AF patients with and without depressed left ventricular systolic function [left ventricular ejection fraction (LVEF)], matched with respect to age, left atrial diameter, and other previously documented confounding clinical variables. After a follow-up of 16 ± 13 months, the complications and success rates for the procedures were not significantly different between cases and controls. Utilizing regression analysis, an enlarged left atrial diameter was the only independent predictor of AF recurrence, regardless of the presence of systolic dysfunction or HF. The authors also describe a significant reverse remodelling effect of effective rhythm control during 6 months of follow-up LVEFs.
How should these results be interpreted? Prior studies focusing on AF ablation in HF patients also demonstrated an improvement in LVEF, cardiac output, exercise tolerance, and quality of life when SR could be achieved after RFCA. Chen et al. reported that SR was maintained in 73% of the HF patients at 14-month follow-up with a non-significant trend towards an improvement in LVEF. Hsu et al. achieved SR after RFCA in 78% of the patients up to 12 months of follow-up. After ablation, LVEF returned to normal in 72% of the patients. 6 , 9 , 10
In the study by De Potter et al. , the recurrence rate of AF after first RFCA procedure was 50% with a potential cure of AF after all redo procedures in 69.4% of the patients with impaired LVEF. About 60% of the patients had persistent AF prior to RFCA with a mean AF duration of 4–7 years. Interestingly, LVEF was improved, although to a lesser extent, even if RFCA had failed to achieve stable SR. Therefore, in HF patients with a reduced LVEF, the reduction of the AF burden might be beneficial to improve systolic and diastolic ventricular function, reduce symptoms, and increase quality of life.
Assessing the total burden of AF requires continuous rhythm monitoring. The need of objectively and continuously monitoring AF burden in HF patients undergoing RFCA will be addressed by the CASTLE-AF study (Catheter Ablation versus Standard Conventional Treatment in Patients with LV Dysfunction and Atrial Fibrillation). In this study, patients with severely reduced LVEF will be randomized to RFCA or conventional therapy for AF after implantation of a dual-chamber implantable cardioverter defibrillator. The study intends to evaluate the hypothesis that morbidity and survival will improve after RFCA compared with conventional treatment. 11
The ablation strategies required for a successful rhythm control strategy in this heterogeneous and complex population are critical. Since HF patients have significantly higher prevalence of persistent and longstanding persistent AF, ablation strategies will require additional targets beyond isolation of the pulmonary veins. In the present study, the ablation is specific to the encirclement of the left and right pulmonary vein antrums and additional lines including the roof and the inferior part of the posterior wall and a mitral isthmus line.
Extrapolating the present data with the reports of Chen et al. and Hsu et al. in comparable HF patient cohorts, AF ablation is an effective treatment strategy for the majority of HF patients with AF. The present study provides evidence that some patients with AF and HF could benefit from restoration of SR. However, further improvements in AF ablation strategies with higher success and lower complication rates will be necessary before ablative treatment of AF may be offered as a first-line therapy for HF patients outside highly experienced centres.
Conflict of interest: none declared.