The purpose of this study is to determine whether heart rate variability-like parameters are related to changes in the disease status of a subject that suffers from a disease that decreases the pumping function of the heart.

Inclusion Criteria:

• Subject has signed and dated the study-specific informed consent form
• Subject is 18 years of age or older
• Subject is expected to remain available for follow-ups
• Subject is able and willing to comply with the protocol requirements
• Subject has predominant Normal Sinus Rhythm
• Subject has systolic Heart Failure and is at the moment of enrollment in NYHA class II or III and has an ejection fraction of less then 40%
• Subject has had a HF-related hospitalization in the past 12 months

Exclusion Criteria:

• Subject needs permanent atrial pacing (> 10%)
• Subject has intermittent 2nd or intermittent 3rd degree block
• Subject has persistent or permanent AF
• Subject has Long QT syndrome, Brugada syndrome, Jervell and Lange- Nielsen syndrome, Romano-Ward syndrome, Andersen-Tawil syndrome or Timothy's syndrome
• Subject has had recent (<2 months) acute coronary syndrome
• Subject has had recent (<2 months) revascularization
• Subject has a pending cardiac transplant or revascularization
• Subject has severe stenotic valvular heart disease
• Subject has severe pulmonary (forced expiratory volume in 1 s < 1 L) hepatic or renal (plasma creatinine > 0.2 mmol/L) disease
• Subject is participating in another study that may affect the results of this study

Systolic Heart Failure Patients with NYHA class II or III and a ventricular ejection fraction of less then 40%.