Atrial fibrillation (AF) has been described as an 'epidemic' due to its increasing prevalence in the ageing population. The prevalence of AF in the UK has risen from 0.78% in 1994 to 1.42% in 2006. The pathogenesis of AF seems to be multifactorial, and includes electrical and structural remodelling, and inflammation. As a result of recent developments in invasive cardiology together with improved pharmacological treatments, cardiac surgeons are increasingly operating on elderly patients with very advanced heart disease and other co-existent diseases. Therefore, AF is often present before cardiac surgery, increasing the risk of surgery and the occurrence of postoperative complications. According to available data, preoperative AF (pre-AF) should be considered as a high-risk marker of postoperative complications, which also significantly reduces long-term patient survival. However, although some multivariate models have concluded that pre-AF seems to be an independent predictor of outcome, this does not prove a cause-effect relationship. Therefore, such a link would need to be proven in prospective randomized studies, yet to be undertaken.