The purpose of this study is to determine whether piboserod, a serotonin-4 receptor antagonist, is effective for the treatment of patients with congestive heart failure.

Despite intensive research for decades, mortality and morbidity in chronic heart failure remains quite high. There is an obvious need for new drugs, especially drugs which may have a different mode of action than the existing ones on the market.

The purpose of this trial is to evaluate whether a new drug candidate, piboserod, has beneficial biological effects in stable outpatients with symptomatic heart failure receiving evidence based treatment for heart failure and to assess safety and tolerability of this treatment.

Inclusion Criteria:

• Clinical diagnosis of CHF (NYHA class II-IV)
• Locally determined LVEF < 0.35 (by CMR, echocardiography, LV angiography, or radionuclide cardioangiography)
• Stable sinus rhythm
• Stable evidence based pharmacological treatment for CHF.

Exclusion Criteria:

• Unstable patients hospitalised within last 2 weeks
• Baseline prolongation of QTc interval
• Atrial fibrillation at randomisation
• MI or re-vascularisation last 3 months
• Stroke last 3 months.