Methods:

Heart failure patients were recruited from multiple centers between 2010 and 2012, into the Chronic Evaluation of Respicardia Therapy prospective nonrandomized feasibility and efficacy study. Recruitment took place among patients with apnea–hypopnea indexes (AHIs) ≥20, with at least one half being central apneas. Patients were excluded if ≥20% apneas were primarily obstructive or heart failure was not stable on medical therapy. Systolic and diastolic heart failure were included. Other exclusions were severe lung disease, creatinine ≥2.5 mg/dl, or any cardiac procedure within the last 3 months. Polysomnograms were done overnight and attended according to standard guidelines before and after implantation. The Remedē System (Respicardia, Inc., Minnetonka, MN) was placed transvenously in the right brachiocephalic vein or left pericardiophrenic vein to provide neurostimulation of the adjacent phrenic nerve, resulting in diaphragmatic stimulation. Sensing of respiration was done by a transvenous lead in the azygous vein. Leads are connected to a generator similar to the size of a pacemaker and placed subcutaneously. The system prevents apneic events by determining appropriate therapy based on device sensors. Device- and procedure-related events were evaluated. The primary endpoint was a change in AHI at 3 months.