Heart failure is frequently associated with cardiac arrhythmias. The aim of the present study was to investigate the effect of levosimendan, a new cardiotonic drug for the treatment of congestive heart failure, on experimental ischaemic arrhythmias. Acute coronary artery occlusion was produced in conscious rats 7-10 days after placement of ligature around the left main coronary artery. Acute pretreatment with levosimendan (0.2 or 0.6 mg/kg orally 1 h before coronary artery occlusion) did not influence the incidence, onset and duration of arrhythmias. Long-term pretreatment with levosimendan (0.2 or 0.6 mg/kg orally twice a day for 2 weeks) increased the survival rate (50% and 81% vs. 44% in controls) and the number of animals without any arrhythmia (37% and 31% vs. 5% in controls). The present results demonstrate that chronic oral treatment with levosimendan could be beneficial in congestive heart failure and arrhythmias resulting from regional myocardial ischaemia.