The primary objective of this study is to compare the Apnea- Hypopnea Index in HF patients with concomitant CSA, after 12 weeks of CRT alone to CRT in combination with one night of overdrive pacing. Secondary objectives are to evaluate the effects of a single night of overdrive pacing applied after 12 weeks of CRT vs. CRT alone on breathing events, sleeping events, and neurohormonal markers. An additional secondary objective of the study is to compare the efficacy of CRT in HF patients with concomitant CSA to HF patients without concomitant CSA.

Sleep apnea is a common and often undiagnosed disorder associated with substantial cardiovascular morbidity and mortality. In recent years studies have been published presenting the relationship between heart failure (HF) and central sleep apnea (CSA). CSA associated with Cheyne-Stokes respiration is a form of periodic breathing in which central apneas and hypopnea alternate with periods of hyperventilation, characterized by a regular crescendo-decrescendo oscillation of tidal volume, which is thought to be caused by dysfunction of central respiratory control. Unlike, obstructive sleep apnea (OSA), CSA likely arises as a consequence of HF.Since 2002, several results have reported on the benefit of atrial overdrive (AOP) pacing in patients suffering from sleep apnea. These results could not be confirmed for obstructive sleep apnea in several subsequent studies. Cardiac resynchronization therapy (CRT) has been proposed as another potential therapeutic pacing approach for CSA by two recently published investigations.The combined therapeutic impact of AOP and CRT (CRT+AOP) so far has not been investigated.We aimed to evaluate the effect of CRT alone and CRT+AOP on CSA in patients with CHF.

Inclusion Criteria:

• Patients with documented clinical history of symptomatic but stable congestive heart failure, NYHA III or NYHA IV, of at least six weeks duration.
• Patient has an indication for a CRT device, or patients with previous pacemaker indication, except Sick Sinus Syndrome, and currently in need for an upgrade to a CRT device
• Patient is scheduled for the implantation of a CRT device
• Patient is over 18 years of age
• Patient provides Informed Consent

Exclusion Criteria:

• Inability to complete overnight sleep study as specified by the protocol
• Myocardial infarction or coronary revascularization procedure within 2 calendar months prior to enrollment
• Planned or strong likelihood of cardiac surgery within 4 months following enrollment
• A spirometric confirmation of obstructive lung disease
• Evidence of obstructive sleep apnea at baseline polysomnography
• Body mass index >30 kg/m²
• Pregnant women