ORLANDO (FRONTLINE MEDICAL NEWS) – Patients with atrial fibrillation (AF) should be screened for obstructive sleep apnea (OSA), because this information may be useful in guiding ablation strategies, according to results of a prospective study.

The study, which associated OSA in AF with a high relative rate of non–pulmonary vein (PV) triggers, has contributed to the “growing body of evidence implicating sleep apnea in atrial remodeling and promotion of the AF substrate,” Elad Anter, MD , associate director of the clinical electrophysiology laboratory at Beth Israel Deaconess Medical Center, Boston, reported at the annual International AF Symposium.

Despite the close association between OSA and AF, it has been unclear whether OSA is a causative factor. Dr. Anter suggested that mechanistic association is strengthening, however.

It has been hypothesized that OSA generates AF substrate through negative intrathoracic pressure changes and autonomic nervous system activation. But Dr. Anter reported that there is more recent and compelling evidence that the repetitive occlusions produced by OSA result in remodeling of the atria, producing scar tissue that slows conduction and produces susceptibility to reentry AF.

A newly completed prospective multicenter study adds support to this latter hypothesis. In the protocol, patients with paroxysmal AF scheduled for ablation were required to undergo a sleep study, an AF mapping study, and follow-up for at least 12 months. A known history of OSA was an exclusion criterion. To isolate the effect of OSA, there were exclusions for other major etiologies for AF, such as heart failure or coronary artery disease.

The AF mapping was conducted when patients were in sinus rhythm “to evaluate the baseline atrial substrate and avoid measurements related to acute electrical remodeling,” Dr. Anter explained.

Of 172 patients initially enrolled, 133 completed the sleep study, 118 completed the mapping study, and 110 completed both and were followed for at least 12 months. Of these, 43 patients without OSA were compared with 43 patients with OSA defined as an apnea-hypopnea index (AHI) of at least 15. Patients in the two groups did not differ significantly for relevant characteristics, such as body mass index (BMI), age, presence of hypertension, or duration of AF; but the left atrial (LA) volume was significantly greater (P = .01) in those with OSA than those without.

Even though the prevalence of voltage abnormalities was higher in the OSA group for the right (P = .01) and left atria (P = .0001) before ablation, the prevalence of PV triggers (63% vs. 65%), non-PV triggers (19% vs. 12%) and noninducible triggers (19% vs. 23%) were similar.

After ablation, PV triggers were no longer inducible in either group, but there was a striking difference in inducible non-PV triggers. While only 11.6% remained inducible in the non-OSA group, 41.8% (P = .003) remained inducible in the OSA patients.

“AF triggers in OSA were most commonly located at the LA septum, at the zone of low voltage and abnormal electrograms, as determined during sinus rhythm,” Dr. Anter reported. “Ablation of these triggers at the zone of tissue abnormality in the OSA patients resulted in termination of AF in 9 (64.2%) of the 14 patients.”

Overall, at the end of 12 months, 79% of those without OSA remained in arrhythmia-free survival, versus 65.1% of the group with OSA that were treated with PV isolation alone.

The lower rate of success in the OSA group shows the importance of specifically directing ablation to the areas of low voltage and slow conduction in the left anterior septum that Dr. Anter indicated otherwise would be missed.

“These zones are a common source of extra-PV triggers and localized circuits or rotors of AF in OSA patients,” he reported. “Ablation of these low voltage zones is associated with improved clinical outcome in OSA patients with paroxysmal AF.”

The data, which Dr. Anter said are consistent with a growing body of work regarding the relationship of OSA and AF, provided the basis for suggesting that AF patients undergo routine screening for OSA.

In patients with OSA, ablation of PV triggers alone even in paroxysmal PAF “may not be sufficient,” he cautioned. “Evaluation of non-PV triggers should also be performed.”

Dr. Anter reported financial relationships with Biosense Webster and Boston Scientific.