The aim of the study is to compare the effectiviness of biatrial pacing versus intravenous administration of metoprolol in the prevention of atrial fibrillation after cardiac surgery

Inclusion Criteria:

• elective CABG and aortic valve cardiac patients,
• previous use of beta blocker

Exclusion Criteria:

• Previous episodes of Atrial fibrillation or flutter,
• II or II degree atrioventricular block, uncontrolled heart failure
• Sick sinus syndrome