Atrial overdrive pacing proved ineffective in most cases of obstructive sleep apnea-hypopnea syndrome, while nasal continuous positive airway pressure showed strong efficacy, according to a comparison study by Greek researchers.
Dr. Emmanuel N. Simantirakis and colleagues at Heraklion (Crete) University Hospital, Greece, implanted dual chamber pacemakers in 16 patients with moderate or severe sleep apnea, documented sleep-related bradycardias, and normal ventricular function (N. Engl. J. Med. 2005;353: 2568–77).
Patients had a mean baseline apnea-hypopnea index of 49 and had at least two self-reported syncopal episodes in the preceding year. Diagnosis of obstructive sleep apnea-hypopnea syndrome was confirmed on polysomnography.
All pacemakers were initially programmed to initiate atrial pacing when the heart rate fell below 40 beats per minute. After 48 hours, half of the patients had their pacemakers programmed for atrial overdrive pacing, with pacing at a rate greater than 15 beats per minute or greater than their normal nocturnal heart rate.
The rest of the patients remained on backup atrial pacing plus nasal continuous positive airway pressure (n-CPAP).
One month later, the groups switched therapies. The researchers then followed the patients for another month.
Atrial overdrive pacing had virtually no effect on the average apnea-hypopnea index at 1 month, which rose from 49 at baseline to 49.2. The increase was not statistically significant. In contrast, n-CPAP significantly improved the average apnea-hypopnea index after 1 month of therapy, which fell from 49 at baseline to 2.7.
The arousal index, desaturation index, and all other variables measured except total sleep time showed improvements with n-CPAP, while atrial overdrive pacing had no measurable effect on the variables, the researchers said.
“We were unable to show any beneficial effect of pacing in reducing the number of episodes of apnea or hypopnea per hour,” the investigators wrote.
The findings of the study, however, may not apply in general to all patients with the obstructive sleep apnea-hypopnea syndrome, they cautioned.
The failure of atrial overdrive pacing to improve symptoms “suggests that overdrive pacing is likely to have a very limited role in this setting,” Dr. Daniel J. Gottlieb of Boston University said in an accompanying editorial (N. Engl. J. Med. 2005;353:2604–6).
“Phenotypes will be identified in which modification of neuromuscular factors will play a useful therapeutic role,” he added.