Introduction: Atrial fibrillation (AF) is common and negatively affects prognosis in patients undergoing co-ronary artery bypass grafting (CABG). However, not all CABG patients develop postoperative AF (POAF), suggesting that a preexisting substrate may contribute to POAF occurrence.

Objective: We therefore assessed the presence and the severity of preexisting atrial proarrhythmic remode-ling in CABG patients who developed POAF compared with those who did not.

Methods: Thirty consecutive patients with stable coro-nary artery disease hospitalized for an elective CABG, free of AF history, were divided according to POAF occurrence into two groups: POAF (n=11) and no POAF (n=19). Surface ECG and Holter ECG moni-toring were performed in all patients prior to CABG. A right atrial sample was collected during the CABG procedure. The presence and the severity of electrical, structural, and autonomic remodeling were evaluated, using P-wave characteristics and expression levels of six genes encoding for ion channels proteins, echocar-diographic and histological analysis, and heart rate va-riability analysis, respectively.

Results: All CABG surgery times were similar in pati-ents with and without POAF (all p>0.05). There were no significant differences between the two groups re-garding electrical remodeling or echocardiographic parameters (all p>0.05). However, POAF patients pre-sented more subepicardial adipose tissue than their non-arrhythmic counterparts (p=0.02), despite similar body mass index (p=0.58). Arrhythmic patients also presented higher preoperative resting heart rate (i.e., a marker of sympathetic activation), and higher root mean square of the successive R-R intervals (i.e., a mar-ker of vagal activation) (both p=0.03).

Conclusions: The present study indicates that POAF is not a random phenomenon and that a preexisting atri-al proarrhythmic remodeling, characterized by autono-mic changes (i.e., sympatho-vagal co-activation) and structural abnormalities (i.e., increased subepicardial adipose tissue), is likely to play a role in POAF occur-rence. Detecting these underlying changes prior to CABG could help to identify AF-prone patients, who would benefit the most from prophylactic antiarrhyth-mic strategies.