DALLAS – A substrate-based ablation strategy failed to show an efficacy advantage over conventional circumferential pulmonary vein isolation for eliminating persistent or paroxysmal atrial fibrillation in a multicenter randomized trial with 232 patients.
High-frequency source ablation (HFSA), a strategy that targets rotors in the atrial substrate responsible for maintaining fibrillation episodes, did not reach statistical significance for noninferiority compared with circumferential pulmonary vein isolation (CPVI) after 6 months in patients with paroxysmal atrial fibrillation (AF), the study’s primary endpoint, Dr. Felipe Atienza said at the American Heart Association scientific sessions.
Mitchel L. Zoler/IMNG Medical Media
Dr. Felipe Atienza
In enrolled patients with persistent atrial fibrillation, adding HFSA to CPVI "offered no incremental value with a trend for an increase in complications," after 6 months in a study designed to test superiority, said Dr. Atienza, an electrophysiologist at Gregorio Marañón University Hospital in Madrid.
But a ray of promise came from 1-year follow-up of the paroxysmal atrial fibrillation patients, half of the patients enrolled in the study. (The other patients had persistent atrial fibrillation.) At that time, HFSA treatment achieved statistically significant noninferiority compared with CPVI for freedom from atrial fibrillation and freedom from atrial tachyarrhythmia, with a significantly lower rate of serious adverse events.
Although the results mean that pulmonary vein isolation remains the standard of care for treating atrial fibrillation patients who fail to respond to drug treatment, substrate-based ablation showed enough potential in the study to remain a viable candidate for further testing, experts said.
"In this trial, HFSA did not improve outcomes in patients with paroxysmal or persistent AF, but the fact that HFSA treatment was equivalent to CPVI in patients with paroxysmal AF keeps the AF substrate and trigger argument alive," commented Dr. Mark S. Link, professor and codirector of the New England Cardiac Arrhythmia Center at Tufts Medical Center Boston, and designated discussant for the report.
"The way to go is to run further investigations like this to try to find and eliminate the substrates of atrial fibrillation instead of ablating everywhere," said Dr. Atienza.
The RADAR-AF (Radiofrequency Ablation of Drivers of Atrial Fibrillation) trial enrolled 115 patients with paroxysmal AF and 117 patients with persistent AF at 11 hospitals in Spain. The researchers randomized the patients with paroxysmal AF to treatment with either HFSA or CPVI; they randomized patients with persistent AF to treatment with both HFSA and CPVI or to CPVI alone. They used software developed by St. Jude Medical to identify the sites for HFSA.
The study’s primary endpoint was freedom from AF while off of antiarrhythmic drugs at 6 months. In the paroxysmal patients, this endpoint was reached by 73% of patients treated with HFSA and 83% treated with CPVI, which failed to meet the prespecified criteria for noninferiority. However, after 1 year the rate of freedom from AF was 69% in patients in both groups, and the rate of freedom from atrial tachyarrhythmia in both groups was 59%, rates that met the criteria for noninferiority. In addition, after 1 year the cumulative rate of serious adverse events was 9% in the HFSA group and 24% in the CPVI group, a statistically significant difference.
Among the patients with persistent atrial fibrillation, the rate of freedom from AF after 6 months was 61% in patients treated with both techniques and 60% in those treated with CPVI alone, which failed to show superiority. Efficacy rates were also similar in both arms after 1 year, and the rate of serious adverse events was 24% in patients treated with both HFSA and CPVI, compared with 10% among those treated by CPVI only.
The RADAR-AF trial was sponsored by St. Jude Medical, which developed the rotor-mapping software used for substrate ablation in the study. Dr. Atienza and Dr. Link said they had no relevant financial disclosures.
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