Arrhythmias after thoracic surgery serve as a marker for increased morbidity and mortality with increased length of hospital stay and use of resources. Early detection and aggressive treatment of hypotension to prevent further tissue/organ damage can improve outcome and prevent further arrhythmias. Major post-operative causes of arrhythmias are hypoxia, pain and electrolyte disturbances. Pain and hypoxia stimulate the sympathetic outflow and cause tachy-arrhythmias. Types of arrhythmias include atrial fibrillation, atrial flutter, and multifocal atrial tachycardia. The clinical importance of arrhythmia in an individual patient is related to the ventricular rate, the presence of any underlying heart disease, and the integrity of cardiovascular reflexes. Atrial arrhythmia can be associated with identifiable factors such as hypoxia, electrolyte imbalance, administration of arrhythmogenic agents such as bronchodilators and catecholamines, myocardial ischemia and heart failure. The major issues in management of patients with AF are related to the arrhythmia itself and to prevention of thromboembolism.