Objective: Leyosimendan is a relatively new inotropic agent. Unlike other inotropic agents, Levosimendan does not increase cellular calcium intake, so that, does not cause intracellular calcium overload and related arrhythmias. Atrial fibrillation (AF) was shown to be an independent risk factor for mortality and morbidity in large heart failure (HF) trials. Heart failure induces AF, AF aggravates HF and therefore they generally coexist. We conducted a study to investigate if there is any differential effect of Levosimendan in HF patients with chronic AF and without AF.