Substudy on the Mechanistic Plausibility of the Clinical Benefits of Adaptive Servo-ventilation

The inclusion and exclusion criteria are mainly those applicable for the parent study; SERVE-HF. The inclusion and exclusion criteria are listed here. INCLUSION CRITERIA FOR SERVE-HF STUDY: * Over 22 years of age * Severe Chronic Heart Failure (CHF) with NYHA class III-IV or NYHA class II with at least one hospitalisation for HF within the last 24 months * Left ventricular ejection fraction (LVEF) less than or equal to 45% by means of echocardiography, radionucleotide angiography, left ventriculography or cardiac MRI documented less than 12 weeks before randomisation * Diagnosis of sleep disordered breathing (SDB) with an apnoea-hypopnoea-index (AHI) of \>15/hr with at least 50% central events and a central AHI of at least 10/hr * Clinically stable with no change in medication and no unplanned hospitalisation for heart failure in preceding month * Optimised medical treatment according to the applicable guidelines * Able to provide informed consent ADDITIONAL INCLUSION CRITERIA FOR THE SUBSTUDY • Predominant central sleep apnoea (apnoea hypopnoea index \> 15/hour with ≥ 50% central events and a central AHI ≥10/hour, derived from full polysomnography (based on total sleep time), documented less than 4 weeks before randomization. Flow measurements have to be performed with nasal cannula EXCLUSION CRITERIA FOR THE SERVE-HF STUDY: * Significant chronic obstructive pulmonary disease (COPD) with Forced Expiratory Volume within one second (FEV1)\<50% predicted * Oxygen saturation at rest during the day 90% at the time of inclusion * Current use of Positive Airway Pressure (PAP) therapy * Life expectancy \< 1 year for diseases unrelated to chronic heart failure * Cardiac surgery, Percutaneous coronary intervention (PCI), Myocardial Infarction (MI) or unstable angina within 6 months prior to randomisation * Implantation of ICD (implanted cardiodefibrillator) or CRT (cardiac resynchronisation therapy) scheduled or within 6 months prior to randomisation * Transient ischemic attack (TIA) or Stroke within 3 months prior to randomisation * Primary hemodynamically significant uncorrected valvular heart disease, obstructive or regurgitant, or any valvular disease expected to lead to surgery during the trial * Acute myocarditis/pericarditis within 6 months prior to randomisation * Untreated or therapy refractory Restless legs Syndrome (RLS) * Pregnancy ADDITIONAL EXCLUSION CRITERIA FOR THE SUBSTUDY * Amyloidosis, hypertrophic obstructive cardiomyopathy or arteriovenous fistulas * Dosage changes of diuretics more than doubled within the last 4 weeks prior to randomisation