Abstract

Background: Atrial fibrillation after cardiac surgery is an important factor for hospital mortality and morbidity. Currently it is postulated that oxidative stress is central in the pathogenesis of postoperative atrial fibrillation (POFA). The oxidative stress corresponds to an imbalance between oxidant species and antioxidant defense systems. The objective of this study is to evaluate the post cardiac surgery plasma antioxidant capacity of patients who develop POFA. Methods: 99 patients undergoing cardiac surgery with extracorporeal circulation (ECC) were evaluated. Two blood samples were collected: one before starting ECC and another 6-8 hours after surgery. Plasma antioxidant capacity was determined by FRAP assay. The diagnosis of POFA was made by electrocardiogram (ECG) continuously within 24-48 hours after the operation, then by Holter monitoring until the fourth postoperative day and finally until discharge by ECG every 12 hours or in the presence of symptoms. The Mann-Whitney U test was used to compare both groups. Results: 32 patients presented POFA (32%). FRAP levels showed no difference in the sample before ECC, but were significantly lower at 6-8 hours post ECC in patients who developed POFA (p <0.05). Discussions/Conclusions: Patients who developed POFA had a lower antioxidant capacity of plasma after cardiac surgery, reinforcing the idea that the oxidative stress is essential in its pathogenesis.