Atrial fibrillation (AF) burden at six months after catheter ablation is predictive of all-cause mortality and heart failure hospitalisation, in AF patients with heart failure and low ejection fraction, according to the findings of a subanalysis of the CASTLE-AF trial, published in JACC: Clinical Electrophysiology.
CASTLE-AF showed that patients treated with radiofrequency catheter ablation rather than traditional drug therapies for AF and heart failure had improved outcomes, including decreasing mortality and cardiovascular hospitalisations.
The CASTLE-AF protocol randomised 363 patients with coexisting heart failure and AF in a multicentre prospective controlled fashion to catheter ablation (n=179) versus pharmacological therapy (n=184).
In their sub-analysis, Johannes Brachmann (Klinikum Coburg, Coburg, Germany), Nassir Marrouche (Tulane University, New Orleans, US) and colleagues sought to evaluate the association between AF burden and clinical outcomes, analysing the effect of lowering AF burden by ablation compared with pharmacological treatment. The subanalysis included 280 patients, 128 of whom underwent ablation and 152 received pharmacological treatment. All patients had implanted dual chamber or biventricular implantable defibrillators with activated home monitoring capabilities. The individual AF burden was calculated as the percentage of the atrial arrhythmia time per day.
Detailing the findings of their analysis, Brachmann, Marrouche et al report that AF burden at baseline was not predictive of the primary endpoint (p=0.473) or all-cause mortality (p=0.446). An AF burden <50% after six months of catheter ablation, was associated with a significant decrease in primary composite outcome (hazard ratio: 0.33, 95% confidence interval: 0.15 to 0.71; p=0.014) and all-cause mortality (hazard ratio: 0.23, 95% confidence interval: 0.07 to 0.71; p=0.031). The risk of the primary endpoint or mortality was directly related to a low (<50%) or high (≥50%) AF burden at six months post-ablation, the authors note.
Additionally, authors demonstrated that the conventional definition of catheter ablation failure (ie recurrence of an AF episode >30 sec) was not predictive of hard outcomes irrespective of the treatment arm, unlike AF burden. These findings highlight the need to determine a new endpoint that defines procedural success.
Summarising the major findings of their analysis, Brachmann et al note that, firstly, AF recurrence as a time-dependent covariate alone did not show any impact, neither on the occurrence of the primary endpoints nor on mortality.
Additionally, they add that catheter ablation significantly decreased AF burden at follow-up in HF patients, whereas no such effect was observed with pharmacological therapy.
Furthermore, they state that the benefit of catheter ablation in reducing the primary endpoint and all-cause mortality was mainly seen in patients with a lower AF burden after the procedure.
Outlining the conclusions, they write: “The 30-s [second] threshold defining AF recurrence after ablation was not a clinically relevant endpoint in HF patients with AF. Instead, the assessment of AF burden after ablation seems like an important indicator of outcomes and procedural success. This potential paradigm shift regarding the definition of a successful treatment concept emphasises the emerging role of implantable devices with diagnostic memory and remote monitoring in the follow-up of ablated patients.”