Phrenic-Nerve Stimulation Implant Diminishes Central Apnea Episodes in Pilot Study

September 24, 2013

ORLANDO, FL — An implantable device that controls breathing muscles during sleep by electrical phrenic-nerve stimulation significantly cut the prevalence of sleep-apnea episodes, primarily by lowering the rate of central sleep apneas (CSA), in patients with mixed central and obstructive forms of the disorder, many of whom also had chronic heart failure[1]. The benefits were evident after three months of use and persisted to at least six months.

"Importantly, these patients slept better," said Dr William T Abraham (Ohio State University, Columbus, OH) when presenting the study here at the Heart Failure Society of America 2013 Scientific Meeting . "Their sleep efficiency was significantly improved, and their time spent in that all-important [rapid-eye-movement] REM sleep was also significantly improved." Those benefits were accompanied by "significant and clinically meaningful improvements" in oxygen desaturation, sleep arousals, and quality of life.

CSA afflicts about 37% of patients with heart failure and is associated with increased mortality and risk of other poor outcomes, Abraham observed. The remedē System (Respicardia), which consists of a pacemakerlike pulse generator with transvenous leads to one of the phrenic nerves, plus an exterior controller box, "delivers therapy in a way that regularizes the breathing pattern so as to avoid the apneas, rather than waiting until the apnea occurs and trying to stimulate the diaphragm to move again," he said. "Just as we use cardiac pacemakers for cardiac rhythm management, this device is designed to deliver respiratory rhythm management."

As discussant following Abraham's presentation of the remedē System Pilot Study, Dr Christopher M O'Connor (Duke University, Durham, NC) said the results were promising but tentative pending larger randomized trials. He said the technique "has been used in the past to support respiratory paralysis, and this new transvenous approach is much less invasive than previous strategies."

Conducted at 11 centers in different countries, the study enrolled patients with CSA by polysomnography conducted within the previous 60 days, with an apnea-hypopnea index (AHI) of at least 20 episodes per hour, only 20% of which could be attributed to obstructive sleep apneas (OSA). The one-fifth of patients with heart failure had to have been stable on standard meds for at least the prior month.

Of the 57 patients slated for implantation of the device, 49 were successfully implanted; the remainder failed due to problems placing the leads. Of those, 47 were available for evaluation of the primary end point, change in AHI at three months. Their apnea was fairly severe; the mean baseline AHI was 49.5.

Sleep Apnea Indexes (Episodes per Hour of Sleep) and REM Sleep Prevalence in Patients Using the remedē System

End points Baseline At 3 mo p
Apnea-hypopnea index 50 22* <0.0001
Central apnea index 28 5 <0.0001
Hypopnea index 15 14 0.481
REM sleep 11% 16% 0.0086

*Primary end point

At three months, patients showed a 56% reduction in AHI, driven primarily by an 82% decline in the CSA index (p<0.0001 for both changes). Blood pressures were unaffected. The benefits persisted, to the same degree of significance, in the 44 patients who were available for evaluation at six months. Abraham said his group is still following the cohort, and there's been no significant letup in the improvements.

"It might not be surprising that these patients also felt better," Abraham said; 76% of patients reported feeling "markedly or moderate" improvement at global self-assessment.

The remedē System Pivotal Trial is currently randomizing patients at about 20 centers. All patients will be implanted with the device, after which it will be turned on in half the cohort but not activated for another six months in the other half. The projected enrollment is 173; Dr Maria Rosa Costanzo (Midwest Heart Foundation, Lombard, IL) is principal investigator.

Abraham discloses receiving consulting fees or honoraria from Respicardia. O'Connor discloses receiving consulting fees or honoraria from Resmed.

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