Endothelin system and atrial fibrillation post-cardiac surgery

Objective We investigated the relation between the endothelin system and atrial fibrillation. Background Endothelin has been implicated in the pathophysiology of atrial fibrillation, but the exact role of A- and B-receptors is unknown. Methods We obtained right atrial biopsies from patients in sinus rhythm and preserved left ventricular function, undergoing off-pump coronary artery bypass grafting. The expression of endothelin, A- and B-receptors was measured using real time reverse-transcribed polymerase chain reaction. Results We studied 52 patients (45 male, mean age 66 +/- 1 years, mean ejection fraction 52 +/- 1%). During a 5-day post-operative period, persistent atrial fibrillation occurred in 15 patients (28.8%). Endothelin mRNA expression was comparable in patients who subsequently developed atrial fibrillation and in those maintaining sinus rhythm. However, the former group displayed down-regulation of endothelin A- (by approximately 60%, p=0.0059) and of B-receptors (by approximately 40%, p=0.0084). The decreased endothelin A-receptor expression could predict atrial fibrillation occurrence (Wilks lambda=0.86, F=6.16, p=0.017). Conclusion Decreased endothelin A- and B-receptor expression is associated with atrial fibrillation after bypass surgery.