Post-operative atrial fibrillation (POAF) is the most common arrhythmia which typically develops 2-3 days after cardiac surgery. The incidence of POAF variates between 10% and 65% depending on the type of cardiac surgery and is especially high in patients which underwent Coronary Artery Bypass Grafting (CABG) and heart valve surgery. POAF is associated with increased morbidity and mortality and has a major impact on hospital resources.

The precise pathogenesis of POAF is very complex, but several studies have demonstrated an association between inflammation, oxidative stress and POAF. Since this oxidative stress may be reduced by dietary anti-oxidantia such as vitamin C, the aim of this study is to evaluate the effect of oral vitamin C administration of the incidence of POAF.

After obtaining informed consent, patients which are planned for CABG or heart valve surgery are randomly assigned into the Vitamin C group or Placebo Group.

Each patient will receive 1 g Vitamin C or Placebo twice a day from 5 days before until 10 days after surgery. The medication will be given orally and both patient and surgeon are blinded for the administrated medication.

Patients receive standard of care in the post-operative period, which includes close monitoring for possible arrhythmias. If such an arrhythmia develops, this is treated according to the normal procedures. All information such as the used medication, the hospitalization / ICU length of stay and the ventilation time is automatically registered in the patient records.

From each patient, three additional blood samples (peri-operative, post-operative Day 0, post-operative Day 1) will be obtained for analysis of Neutrophil gelatinase-associated lipocalin (NGAL), a possible marker of subclinical kidney damage. These samples will be analysed in batch once all samples are collected.

Inclusion Criteria:

• signed informed consent
• eligible for elective cardiac surgery
• preoperative sinus rhythm

Exclusion Criteria:

• patients who do not want to participate