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Nerve stimulation tested in central sleep apnea.

CHICAGO -- First-in-man results of a fully implantable system for chronic phrenic nerve stimulation for treatment of central sleep apnea in heart failure patients showed significant improvements in the periodic breathing pattern that were sustained and even enhanced during 1 month of therapy, a study has shown.

Participants in this small pilot study were recipients of the RespiCardia system, which consists of a fully implantable pulse generator and transvenous stimulation lead, Dr. William T. Abraham said at the meeting.

In the study's acute phase, 13 heart failure patients with central sleep apnea marked by Cheyne-Stokes breathing with oxygen desaturation, central apneic episodes, and disrupted sleep architecture underwent two overnight sleep studies. On one night, patients received no treatment. On the other night, they received phrenic nerve stimulation with the generator remaining outside the body.

Three patients then underwent implantation of the full RespiCardia system. After a month-long healing period during which the system remained off, they returned for two overnight sleep studies: the first with the system off, the second with it switched on for the first time. A month later, they were back in the sleep lab for another overnight study--this time to assess the effects of 1 month of treatment, explained Dr. Abraham, professor of internal medicine, physiology, and cell biology and director of the cardiovascular medicine division at Ohio State University, Columbus.

The acute benefits observed in the 13 patients during a single night of therapy, compared with no treatment, were replicated in the 3 patients with the implanted system--and those benefits were even greater after a month of treatment. For example, the mean apnea-hypopnea index at baseline was 34.3 events per hour of sleep, compared with 18.9 during the first night of treatment and 12.0 after 1 month of phrenic nerve stimulation.

Similarly, the other respiratory parameter assessed in the study--the central sleep apnea index--improved from 18.0 episodes per hour at baseline to 4.3 on the first night of treatment and 0.5 after a month of chronic phrenic nerve stimulation.

Nocturnal oxygen desaturation also improved markedly, as shown by mean 5% oxygen desaturation index scores of 35.4 at baseline, 20.0 on the first night of therapy, and 12.4 after 1 month.

Sleep architecture as reflected in the arousal index improved from a mean of 20.1 arousal episodes per hour at baseline to 8.0 on night 1 and 7.6 after 1 month of therapy.

The pulse generator can be implanted in either the right or left pectoral location, depending on whether a heart failure patient has another device already in place. The stimulation lead is placed in the pericardiophrenic vein. An optional transthoracic impedance sensing lead can be placed in the azygos vein to monitor respiration.

Dr. Abraham said the next step in the development of the RespiCardia system is to determine whether the improvements in oxygenation, sleep architecture, and central apneic episodes seen in this preliminary month-long study are maintained in larger numbers of patients over longer periods, and more importantly whether these sleep-lab benefits translate into improved heart failure status and quality of life.

He said he serves as a modestly compensated consultant to Cardiac Concepts, which sponsored these studies and is developing the RespiCardia system.


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Title Annotation:CARDIOLOGY
Author:Jancin, Bruce
Publication:Internal Medicine News
Date:Mar 1, 2011
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