Postoperative atrial fibrillation (POAF) is associated with increased mortality and morbidity in patients undergoing isolated coronary artery bypass grafting (CABG). It has been estimated that 5-40% of CABG patients experience POAF. Advanced age, P wave abnormalities, left atrial dilation, emergency surgery, low left ventricle ejection fraction, low glomerular filtration rate and chronic obstructive pulmonary disease have been reported in the etiology. Predicting which patients would experience POAF following CABG is important since it would allow physicians to apply more focused prophylactic measures. Lactate is the final product of anaerobic glycolysis. Serum lactate level are increased in case of inadequate oxygen delivery to tissues. The investigators aim to assess whether serum lactate levels measured early in the postoperative period could be used as a predictive marker of POAF in adults undergoing isolated CABG.

Inclusion Criteria:

• Undergoing isolated CABG
• Age >18 years

Exclusion Criteria:

• Age <18 years
• Pregnancy
• History of paroxysmal atrial fibrillation prior to surgery
• Undergoing concomitant procedures (e.g., CABG + valve surgery)
• Any preoperative cardiac rhythm other than normal sinus rhythm
• More than mild cardiac valve stenosis or insufficiency

All consecutive adult patients undergoing isolated CABG during the study period in the Department of Cardiovascular Surgery at Basaksehir Cam Sakura City Hospital will be evaluated for possible enrollment.