OASIS: Rotor-Guided Ablation Tanks in Atrial Fibrillation

Patrice Wendling

May 10, 2016

SAN FRANCISCO, CA — The first randomized study comparing three ablation strategies in persistent or long-standing nonparoxysmal atrial fibrillation (AF) showed that targeting electrical rotors in the heart did little more than add to procedure and radiofrequency times[1].

Focal impulse and rotor modulation (FIRM)–guided ablation, which has been around for about 5 years, failed to reduce AF/atrial tachycardia (AT) recurrences and resulted in significantly lower freedom from AF/AT off antiarrhythmic drugs when added to pulmonary-vein isolation (PVI).

"Our community should push, demand this kind of result earlier on, because after all it is not fair for the patient to go on with a procedure that has proven not to be effective," principal investigator Dr Andrea Natale (Texas Cardiac Arrhythmia Institute, Austin) said during a press briefing before formal presentation of the OASIS trial at the Heart Rhythm Society (HRS) 2016 Scientific Sessions.

At 12 months of follow-up, the primary end point of freedom from any recurrent AF/AT without antiarrhythmic drugs occurred in 14% of patients with FIRM-only, 52% with FIRM plus PVI, and 76% with standard PVI plus posterior wall (PW) and non-PV trigger ablation (log rank P<0.0001).

"I don't think it's the end of this technology, but certainly it's a study that does raise some question about the validity of this approach," he added.

Dr Lucas Boersma (St Antonius Ziekenhuis, Nieuwegein, Netherlands), who was not involved in the study, told heartwire from Medscape, "I don't think it's the end of mapping. There are other systems coming along like CardioInsight, Acutus that have options to have very high-resolution mapping to see in each individual patient what the reason for their AF is. We are now treating every patient like AF is one disease, and if you do a standard approach, you cure the patients. But what we are learning from the past 10 to 15 years is that there is only one AF patient and that's the patient sitting in front of you."

Natale said it's possible that the system's software may not be appropriate or that the expandable 64-electrode basket at the tip of the FIRMap catheter (Abbott) doesn't provide global coverage. "No matter the way you shape the mapping catheter, the basket is never going to cover the entire surface of the left atrium," he said. "The right atrium, we think that's less of an issue."

Nonrandomized data have shown a benefit with FIRM-guided ablation alone or with PVI, but Natale pointed out that there are also animal and human studies using epicardial mapping with 500 electrodes supporting the idea that rotors are not really that important or cannot be detected.

"Unless there is a new version of rotor mapping that I feel is significantly different, probably in my lab and probably in the lab of other . . . investigators, this will be the end of rotor ablation with this system," he said. "I think the community is kind of split between the believer and the nonbeliever; I am not [a believer]."

Stopped for Futility

OASIS randomly assigned 113 patients from two US centers and one German center undergoing first-time AF ablation to FIRM-only (n=29; 28% female), FIRM plus PVI (n=42; 33% female), or PVI plus PW and non-PV trigger ablation (n=42; 31% female). FIRM mapping was repeated until all rotors were identified and ablated or AF organized into AT or converted to sinus rhythm. Focal drivers or rotors were detected in all FIRM patients (mean 4.0 per patient FIRM-only; 4.2 FIRM-PVI).

Rotor mapping and ablation added to the duration of the procedure, which averaged 131 min with PVI plus PW and non-PV trigger ablation vs 222 min with FIRM-alone and 233 min with FIRM plus PVI ( P<0.001). Radiofrequency times were also longer with rotor mapping (29 vs 49 vs 33 min; P<0.001), according to the data, simultaneously published in the Journal of the American College of Cardiology.

No procedure-related adverse events occurred with FIRM-alone, but the arm was stopped early for futility after a relatively high rate of recurrence triggered an unplanned interim analysis.

FIRM plus PVI ablation was associated with a significantly higher rate of recurrence in multivariable analysis adjusted for sex and AF type (2.36; P=0.027).

Press briefing moderator Dr Thomas Deering (Piedmont Heart Institute, Atlanta, GA) said, "I think atrial-fibrillation ablation is a work in progress. We are determining more and more what the mechanisms are, but I still feel we are in the early stages."

Natale reported speaker honoraria from Boston Scientific, Biosense Webster, St Jude Medical, Biotronik, and Medtronic and serving as a consultant for Biosense, St Jude, and Janssen Pharmaceuticals. Disclosures for the coauthors are listed in the article.

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