When it comes time to perform AF ablation, many ask the question: Should we freeze or burn? Which technique of pulmonary-vein isolation (PVI) is best?
The two most common techniques for PVI are point-to-point RF ablation and cryoballoon ablation. Heat or cold? Fire or ice? Dots or circular lines? At electrophysiology meetings, this is a hot—not cold—topic.
We debate this issue because there is currently far more eminence than evidence. Trials comparing the two strategies have been limited by small numbers of patients, nonrandomized designs, and single-center experiences. A recent meta-analysis of these small studies showed equipoise for safety and efficacy[1]. A German registry of 3775 nonrandomized consecutive patients with AF also reported comparable outcomes[2]. The FIRE AND ICE trial will fill that void; it is a large multicenter randomized clinical trial that has finished recruiting patients.
But even when FIRE AND ICE is reported, there will still be the matter of generalizing data from experienced centers to the real world.
Here, I think it best to consider this debate from a patient's viewpoint. In other words, if you were the patient, which technique would you choose?
One factor you would consider is the experience of the doctor and center. Both techniques of AF ablation require skill, but most electrophysiologists would agree that point-to-point RF ablation demands more time and procedures to master. Compared with the one-shot PV isolation with a cryoballoon, RF ablation involves intricate movements and delivery of many singular lesions to isolate the vein. Where an operator is on this experience curve may be an important factor in comparing the efficacy and safety of the procedure.
An abstract in the young investigators award presentations at Europe an Heart Rhythm Association (EHRA) EUROPACE-CARDIOSTIM 2015 sheds light on the relationship between experience and outcomes of the two PVI techniques.
Dr Rui Providencia (Clinic Pasteur of Toulouse, France) presented results of an observational study from six centers involved in the FrenchAF registry[3]. For this analysis, the research team included only centers performing more than 100 procedures per year. The characteristics of the patients were typical of those with paroxysmal AF. The CHA2DS2-VASc score was slightly higher in the cryoablation group (1.6 vs 1.4, respectively). The primary outcomes were AF suppression and safety.
Four of the six centers fulfilled entry criteria for the study. There were differences in experience at these centers. One center did only cryo, one did mostly cryo, one did mostly RF, and the largest-volume center was evenly split. Average follow-up was 30 months.
Results
In overall safety, researchers noted no significant differences (5.9% for cryoablation vs 6.0% for RF ablation). As expected, they observed seven phrenic-nerve injuries (1.9%) with cryoablation and none with RF.
For cryoablation, the four centers performed nearly identically. Kaplan-Meier curves were superimposable, and overall rates of success varied from 78 to 81%.
For RF, the three centers varied in success rates according to procedure volume: 81.3% in the center performing more than 150 RF ablations per year, 61.5% in one performing close to 100, and 44.1% in the one performing less 70 AF RF ablations (P<0.001).
When pooling the success rates of the four centers, cryoablation, compared with RF ablation, resulted in a nearly 40% reduction of AF recurrences over 30 months (HR 0.59, CI 0 0.43–0.82; P=0.002).
This difference was driven by procedural volumes. In high-volume RF ablation centers, the success rates of cryoablation and RF ablation were comparable, whereas in lower-volume centers, cryoablation outperformed RF.
Dr Providencia began his discussion by noting this was a nonrandomized retrospective study in only four centers. He also mentioned that cryoablation was performed with the first-generation balloon, and the current standard of care is to use the second-generation balloon. (I am drawn to presentations in which the speaker begins with limitations before strengths. Such an order helps with framing the findings.)
He then concluded that cryoballoon ablation was safe and efficacious as a first procedure, outperformed RF in low-volume centers. and produced consistent results independent of center experience.
In the Q&A after the talk, Dr Karl-Heinz Kuck (Asklepios Klinik, Hamburg, Germany) said he fully agreed that to do a cryoballoon procedure requires less of a learning curve than an RF ablation procedure, but he was concerned about the RF technique in this study. Were they confirming PVI, for instance? (That question illustrates one aspect of critically appraising a study. Namely, was the comparator arm legitimate? Keep in mind that one way studies can be biased is stacking the deck in favor of one group.)
Dr Providencia strengthened his case when he confirmed that RF centers were doing standard PV isolation with confirmation of block. In fact, he told the audience these centers had been "doing RF for 10 years, and cryoablation for just two years, and the results were already better with cryoablation."
My Take-home
This abstract deserves mention for five reasons:
First, it is consistent with my personal experience. It took me years to learn point-to-point RF ablation but only months to learn cryoballoon ablation.
Second, it highlights an increasingly important facet of electrophysiology. Procedural volume, experience, and training matter. A sobering analysis of more than 93,000 AF ablation procedures (performed between 2000 and 2010) revealed the rate of in-hospital complications remained steady at 6.29%[4]. A significant association between volume and adverse outcomes was noted, with operators doing <25 procedures a year or hospitals doing <50 procedures having worse outcomes.
Third, it provides actionable patient-centered outcomes. If you are a person choosing between invasive procedures, it helps to know the degree to which volume and experience affect outcomes. Indeed, cryoballoon ablation seems less dependent on operator and center experience.
Fourth, these findings have implications for electrophysiology training programs. One advantage of the long learning curve of point-to-point RF isolation is it hones the neural pathways required for second and third left atrial ablation procedures. The unfortunate truth of AF ablation is that multiple procedures are often required—especially when treating patients with later-stage disease. It would be a shame if young doctors didn't learn the feel of moving catheters in the left atrium.
Finally, this study won the young investigators competition. That is a big honor.
JMM
Cite this: Fire or Ice for AF Ablation? Operator Experience Counts - Medscape - Jun 24, 2015.
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