Discussion
cryo-applications, Atrial Fibrillation, Stroke
ATRIAL FIBRILLATION, COMPLICATIONS, STROKE
The AVATAR-AF trial has shown that a streamlined approach to AF ablation was superior to drug therapy at avoiding hospital-based treatment for AF. This was primarily driven by recurrent symptoms leading to outpatient consultations. The standard catheter ablation approach did not demonstrate superior outcomes to the streamlined AVATAR approach. All three arms had significant improvement in quality-of-life measures over the year, but there was no difference between the AVATAR arm and the two control groups.AVATAR-AF reports the outcomes from AF treatments on the basis of being able to avoid hospital episodes including consultations and admissions. We believe this provides a measure of symptom burden that is easy for patients to understand and is a relevant metric to healthcare providers. Similarly, the recent Early Treatment of Atrial Fibrillation for Stroke Prevention Trial 4 (EAST-AFNET 4) showed benefit using a clinically unambiguous composite endpoint to confirm that trying to maintain sinus rhythm using drugs, cardioversion and ablation was superior to rate control in AF.AVATAR-AF is also the first randomized trial to simplify ablation therapy. The cryo-balloon is unique in not requiring intracardiac electrical recordings to deliver therapy. It is manipulated around the PV ostium until occlusion of PV flow can be demonstrated using a contrast injection under fluoroscopy. Cryotherapy delivered during complete PV occlusion is associated with a very high rate of PV electrical isolation enabling the streamlined ablation protocol.In addition, we analysed the procedural parameters post-hoc and more patients had two cryo-applications in all veins in the AVATAR group (as per protocol) compared to the conventional ablation. Amongst all patients having ablation, the use of two applications was associated with fewer endpoints. This suggests that receiving two cryo-applications per vein was more important than proving electrical isolation. This raises important questions about how best to achieve durable PVI.The main limitation of our study design was that we assumed the prevailing view that ablation with PV mapping would be superior to the AVATAR approach. A non-inferiority study would be required to determine if the two approaches are indeed equivalent.AVATAR-AF demonstrates that the ablation procedure can be simplified and streamlined and still be superior to medical therapy using practical patient-based outcomes across a broad range of patient groups. This potentially allows the AVATAR approach to be delivered in cardiac catheter labs without specialist electrophysiology equipment and associated expert staff. Similarly, the operator would have to be expert in accessing and manipulating catheters in the left atrium, as well as managing complications, but would not need to be able to interpret intracardiac electrograms. This ‘streamlining’ would increase the capacity for delivering AF ablation, even though we did not expect the AVATAR protocol to have an impact on procedure times. Reducing this resource requirement has broad implications for where and how the treatment is delivered and could promote more widespread provision of AF ablation. We did not test this directly in AVATAR-AF, but we have the clinical justification to proceed to such studies, especially given the increasing demand for AF therapy.We conclude that patients with symptomatic paroxysmal AF can be treated effectively by a streamlined ablation approach using a cryo-balloon.