Preventive AF Ablation? Maybe, If Added to Atrial-Flutter Ablation

May 14, 2014

SAN FRANCISCO, CA — Add-on ablation for pulmonary-vein isolation (PVI) in patients already undergoing standard isthmus ablation for clinical atrial flutter (AFL) was followed by a steep drop in risk of new-onset atrial fibrillation (AF), as well as, for those developing the arrhythmia, significantly reduced AF burden, in a small, randomized proof-of-concept study[1]. The benefit of preventive PVI ablation came at the cost of greater procedural and fluoroscopy time but not of more complications.

Although such AFL ablation is usually successful, perhaps half of treated patients go on to develop AF, which seems to share a mechanism with the abolished AFL that ablation didn't address, according to Dr Jonathan S Steinberg (Valley Health System, New York, NY).

"The pathophysiology underlying atrial flutter strongly suggests that virtually all flutter patients will develop AF," according to Steinberg. In actual practice after this kind of AFL ablation, he told heartwire , "roughly a third of our patients then have to get a pulmonary-vein ablation anyway," depending on later AF burden and symptoms.

So the study's patients represented a good group in which to test PVI ablation to reduce risk of new-onset AF, he said, that was supported by their high prevalence of AF risk factors, including hypertension and left atrial enlargement. But, "Ultimately other groups may be ripe for [pulmonary-vein] targeting as well, [those] who have plenty of risk and incidence."

Steinberg presented the randomized, single-blind Prophylactic Pulmonary Vein Isolation During Isthmus Ablation for Atrial Flutter (PREVENT AF) study here last week at the Heart Rhythm Society 2014 Scientific Sessions and is first author on the trial's publication this week in Heart Rhythm [1].

Fifty patients without AF but undergoing cavotricuspid isthmus ablation for recurrent paroxysmal or persistent AFL were assigned to also receive or not receive same-session PVI ablation. All patients received an implantable cardiac monitor to document atrial arrhythmias. They were followed for a year after a three-month blanking period. None received antiarrhythmic drug therapy after ablation but all received oral anticoagulation for at least a month after the procedure.

Total procedure time averaged 168 minutes for the isthmus/PVI-ablation group, more than twice as long as for the isthmus-ablation-only group (p<0.0001). Mean total fluoroscopy time was at least fourfold higher, at 27.5 min vs 6.2 min for isthmus ablation only (p<0.0001) .

AF burden was similar during the blanking period, but significantly more patients in the AFL-ablation-only group went on to experience new-onset AF over the 12-month follow-up, at a hazard ratio of 8.72 (p=0.003). There were no strokes.

Rates of New-Onset AF and AF Burden, AFL Isthmus Ablation With vs Without PVI Ablation

End points Isthmus ablation only (%) Isthmus ablation with PVI (%) p
*12-mo new-onset AF 52 12 0.003
Blanking-period AF burden 4.2 4.0 0.96
6-mo AF burden 8.1 4.0 0.005
12-mo AF burden 8.3 4.0 0.002
*Primary end point
AF=atrial fibrillation
AFL=atrial flutter
PVI=pulmonary-vein isolation

A later PVI-ablation procedure was performed for "recurrent and highly symptomatic AF" at physicians' discretion in 32% of patients who had been randomized to AFL ablation only, but in none of those randomized to AFL ablation with preventive PVI (p=0.004). Antiarrhythmic drug therapy was initiated in 40% and 8% of patients, respectively (p=0.005). In no case was there recurrent AFL.

In multivariate analysis, the only variable to be significantly associated with new-onset AF was randomization to preventive PVI vs AFL ablation only, for a hazard ratio of 0.21 (95% CI 0.05–0.89, p=0.036).

"Prophylactic PVI is a new treatment concept and must be well validated before it's introduced into clinical practice," Steinberg said in his live presentation of the study. "Although we have demonstrated the feasibility of this approach and have succeeded in reducing AF incidence, that is, proof of principle, more robust clinical outcomes must be examined in larger data sets to establish the ultimate net clinical value of prophylactic PVI."

Once those trials are done, and if the current findings are confirmed, PVI ablation could expand dramatically as a procedure, Steinburg said when interviewed. A big remaining question is whether the addition of preventive PVI, with its extra procedure time and radiation exposure, is worth the added risk. "That's what we have to figure out. Procedural risk is very small in present-day experienced labs, when you consider only serious risks—offset by a much higher clinical risk from the impact of AF occurrence if [preventive PVI] isn't done."

Steinberg discloses consulting for Boston Scientific, Medtronic, St Jude Medical, Biosense Webster, Cameron Health, Topera, AliveCor, Sanofi, Janssen, Philips, and Ambucor; receiving research support from Medtronic, Biosense Webster, and Boston Scientific; and being a speaker for Bristol-Myers Squibb, Pfizer, and Medtronic.


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