A prospective observational multi-centre study for the validation of the ApneaScan algorithm (integrated in ICD devices (with or without cardiac resynchronization therapy function) of the "Incepta" series for the screening of sleep disordered breathing in patients with stable symptomatic chronic heart failure, using portable polygraphy monitoring device ("Embletta Gold") as reference for the Apnea-Hypopnea-Index (AHI).