Aim: Atrial fibrillation (AF) after coronary artery bypass surgery (CABG) is the most common type of arrhythmia and it causes serious morbidity. Low levels of triiodothyronine (T3) hormone are thought to be a strong determinative factor on poor prognosis of cardiac patients. This study was planned to investigate the effect of low levels of T3 on the development of AF after off-pump coronary artery bypass surgery (OPCAB) and conventional CABG surgery.

Methods: The study was prospectively planned on 60 patients undergoing CABG surgery. Thirty of them were randomly selected among the patients undergoing OPCAB, and the other 30 were randomly selected among the patients undergoing conventional CABG surgery. Thyroid function profiles of all patients were evaluated before the operation and on the first day of postoperative period.

Results: The average age of the patients was 58.7± 8. After the operation, 3 patients from each group, 6 patients in total, developed AF. Postoperatively measured TT3 levels of the patients who developed AF after the operation (0.39±0.09) were found to be significantly lower than the preoperatively measured TT3 levels (0.97± 0.06) (p=0.042). Moreover, postoperatively measured fT3 levels of the patients who developed AF after operation (1.58± 0.30) were found to be significantly lower than the preoperatively measured fT3 levels (2.95±0.37) ( p=0.001). However, by univariate logistic regression analysis, it was seen that the variables that were thought to be risk factors for AF were not significantly effective. Also, when the effects of the variables were examined together by multivariate regression analysis, no significant result was found.

Conclusion: In our study, it was seen that low levels of thyroid hormone in patients undergoing OPCAB and conventional CABG surgery had no effect on AF development.

Keywords: thyroid hormone, atrial fibrillation, off-pump coronary artery bypass, conventional coronary artery bypass.