Atrial fibrillation (AF) is the most common arrhythmia after cardiac surgery. The incidence of AF varies between 20 - 45 % after (coronary artery bypass grafting) CABG. It may lead to hemodynamic compromise, thromboembolic events, increased length of stay in the hospital and increased morbidity. The underlying cause of AF has been related to a variety of factors. Those most commonly related to the intraoperative management are the use of cardiopulmonary bypass (CPB), the influence of systemic inflammation, myocardial damage, intraoperative fluid management and the need of red blood cell transfusion.

The purpose of the study is to find out the difference in the incidence of atrial fibrillation after CABG when using the conventional (CECC) or mini bypass system (MECC).

The treatment protocol is similar in both groups except the CPB method (CECC vs. MECC). In both methods the investigators use MAQUET tubing and oxygenator. The investigators also collect special blood samples for determining most relevant factors found affecting in the incidence of AF.

Atrial fibrillation (AF) is the most common arrhythmia after cardiac surgery. The incidence of AF varies between 20 - 45 % after (coronary artery bypass grafting) CABG. It may lead to hemodynamic compromise, thromboembolic events, increased length of stay in the hospital and increased morbidity. The underlying cause of AF has been related to a variety of factors. Those most commonly related to the intraoperative management are the use of cardiopulmonary bypass (CPB), the influence of systemic inflammation, myocardial damage, intraoperative fluid management and the need of red blood cell transfusion.

The purpose of the study is to find out the difference in the incidence of atrial fibrillation after CABG when using the conventional (CECC) or mini bypass system (MECC). There has been some evidence in retrospective studies comparing conventional and mini bypass systems that the incidence of AF after mini bypass could be statistically lower.

With the prospective randomized study protocol patient demographic will be similar regarding other variables such as age, gender, previous history of AF, use of beta blockers etc. Only isolated CABG procedures will be included. The amount of patients needed in the study has been calculated so that when the investigators assume that the incidence of AF is normally 45 % and with the mini bypass system the investigators can reduce it to 25 %, the investigators need 330 patients (165 in each group) to show this with the power of 0,8 (a 0,05).

The treatment protocol is similar in both groups except the CPB method (CECC vs. MECC). In both methods the investigators use MAQUET tubing and oxygenator. Fluid management and the use of inotropic agents are standardized and followed by using pulmonary artery catheter. After the operation in the ICU the investigators also use a standardized treatment protocol in the fluid management and in the medication. Patients are ECG-monitored 48 hours after the operation. Possible arrhythmias are documented until the patient is discharged from the hospital.

The investigators also collect special blood samples for determining most relevant factors found affecting in the incidence of AF (IL-6, IL-8, PAI-1).

Inclusion Criteria:

• Elective CABC patients

Exclusion Criteria:

• Previous episodes of AF of flutter
• Contraindications for betablocker use
• Sick sinus syndrome
• II or III degree atrioventricular block
• Uncontrolled heart failure
• Previous medication of corticosteroids and immunosuppressive medication
• Emergency surgery