Background: Studies of the association between post operative AF and Plasma level of NT- Pro BNP have reported conflicting findings. The aim of the present study was evaluation of the association between post coronary bypass graft- Atrial Fibrillation (AF) and Plasma level of NT- ProBNP as an independent risk factor of AF development in patients undergoing coronary artery bypass graft.

Methods: In a cohort study, 79 patients with sinus rhythm who admitted in Imam Khomeini Hospital in Tehran, Iran, during February 2009 and February 2010 for CABG are included the study and followed for developing post operative AF rhythm.

Results: Post operative AF was found in 17.7% of patients. The peak time from the operation to the first AF episode was in second post op day in ten patients (71.4%). The serum level of ProBNP in patients with AF was significantly higher (1624± 647 versus 221± 238 pg/ml, p< 0/0001). Increased age, Increased LA size and high plasma level of ProBNP were associated with increased risk for post op AF. After adjustment of risk factors, plasma level of ProBNP was the most important risk factor with odds ratio of 15.34 with CI 95% 1.77-132.95 and then LA diameter with odds ratio of 6.11 with CI 95% 0.99-37.42 was independently correlated with post op AF. Correlation between plasma level of ProBNP with age and LA size was seen too (LA size r = 0.0281, p= 0.012). Between age and ProBNP (r= 0.337, p= 0.002). The best cut off point for plasma ProBNP as a predictor of post op AF was 854 pg/ml.

Conclusion: Increased level of preoperative ProBNP levels could be an independent predictor of post operative Atrial Fibrillation.