ABSTRACT
A 46-year-old male patient, who underwent decortication with right poster lateral thoracotomy developed atrial fibrillation in the postoperative period, which was identified with continuous ECG monitoring. He was managed with parenteral beta blockers, hydrocortisone, oxygenation and IV fluids. The patient was investigated thoroughly for the cause of atrial fibrillation in addition to the preoperative evaluation. As the patient had no obvious risk factors such as cardiac failure, hypertension, ischemic heart disease, rheumatic heart disease or alcoholic intoxication he was ultimately assessed for the thyroid function. The thyroid profile showed extremely low levels of thyrotropin (TSH) with elevated T3, T4 levels. Patient was treated with carbimazole and Propranolol to which he responded.