Post-operative atrial fibrillation (POAF) is a major cause of morbidity and mortality after a cardiac surgery. Both systemic inflammation and oxidative stress play a role in the initiation of POAF after a cardiac surgery. Epidemiological studies show a significant inverse correlation between cardiovascular risk and consumption of polyphenol-rich foods (PRFs), due to antioxidant, vasorelaxant and antithrombotic properties of their polyphenolic components. The main objective of this study is to evaluate the effect of polyphenol-rich food supplementation on post-operative atrial fibrillation (POAF) in patients undergoing an open heart surgery (mainly coronary artery bypass grafts (CABG) and valve replacement or repaired (VR))