Radiofrequency vs Cryoablation: both prove equally good in the RACE-AF study.

Recurrent paroxysmal atrial fibrillation (PAF) after catheter ablation is presumably caused by failure to achieve durable pulmonary vein isolation (PVI). The primary methods of PVI are radiofrequency (RF) and cryoballoon (CRYO) catheter ablation, but these methods have not been directly compared with respect to PVI durability and the effect thereof on AF burden. Recent research by Sorensen et al, in Circulation, the RACE-AF Randomized Controlled Trial, has shown that PVI by RF and CRYO catheter ablation produce similar moderate to high PVI durability and both treatments lead to marked reductions in AF burden.

Pulmonary vein isolation (PVI) is the cornerstone of catheter ablation of atrial fibrillation (AF), and the two primary methods to achieve PVI are radiofrequency (RF) and cryoballoon (CRYO) ablation, with the latter being a more recently established, simpler alternative with shorter procedure time and steeper operator learning curve as shown in CryoAF trial, Early AAF trial, etc.

Recent trials have shown comparable clinical outcomes, and studies with mandatory invasive PVI reassessments after CRYO ablation have reported PVI durability similar to analogous RF studies. But two questions remain unanswered: How do the two methods compare in achieving durable PVI? And how does PVI durability relate to clinical outcomes?

The RACE-AF Trial was a single-center, prospective, randomized, patient-controlled, clinical trial aiming to assess the durability of PVI and AF burden after RF vs. CRYO catheter ablation for paroxysmal AF (PAF), and additionally, to evaluate the effect of PVI durability on AF recurrence and burden. The trial included insertion of an implantable cardiac monitors (ICM) prior to ablation and protocol-mandated invasive reassessment of PVI status, irrespective of AF recurrence.

Trial included 98 patients with PAF assigned 1:1 to PVI by contact-force sensing, irrigated RF catheter or second-generation CRYO catheter. Implantable cardiac monitors were inserted ≥1 month before PVI for assessment of AF burden and recurrence, and all patients, irrespective of AF recurrence, underwent a second procedure 4-6 months after PVI to determine PVI durability.

Researchers found that in the second procedure, 76% pulmonary veins were found durably isolated after RF and 81% after CRYO, corresponding to durable isolation of all veins in 47% of patients in both groups.

Median AF burden before PVI was 5.4% vs. 4.0%, RF vs. CRYO, and reduced to 0.0% and 0.0, respectively – a reduction of 99.9% and 99.3%.

AF burden after PVI significantly correlated to the number of durably isolated PVs (p < 0.01), but 20% patients with durable isolation of all veins had recurrence of AF within 4-6 months after PVI.

This is the first randomized comparison of RF and CRYO ablation for PAF with a protocol mandated invasive reassessment of PVI durability, and the first study to use continuous ICMmonitoring to assess the impact of PVI durability on AF burden. The main result of the study is that CF sensing RF and second-generation CRYO ablation were equally efficient to produce durable PVI, with close to 80% of PVs being durably isolated. The study furthermore found that the two ablation methods produced a marked, and highly similar reduction in AF burden, and that PVI durability was related to reduction in AF burden and recurrence.

"Thus, our study adds new insight into this complex relationship: while durable isolation of all PV's is clearly associated with reductions in AF burden and recurrence, it is not sufficient to prevent even short-term AF recurrence in one fifth of PAF patients", noted that authors.

20% of patients with durable PVI had AF recurrence within 4-6 months. One clinical implication of this is that simply reisolating PVs in reablations in many cases will be insufficient to prevent any recurrence of AF.

Source: Circulation https://doi.org/10.1161/CIRCEP.120.009573