It is well known that abnormal heart beats from the top parts of the heart, atrial fibrillation (AF) and atrial flutter (Aflut), occur frequently after most types of cardiac surgeries. Postoperative AF and Aflut are associated with significant morbidity, longer hospital stay, and higher related costs. Currently therapies are marginally effective at preventing this abnormal heart beat. The incidence of abnormal heart beats after cardiac surgery seems to be a function of the amount of inflammation and oxidative stress induced. Our group and others have shown that atrial abnormal heart beats are associated with increased oxidative stress. Thiazolidinediones (TZDs) are medications used to treat diabetes. Beside their glucose lowering effects, TZDs are shown to exhibit anti-inflammatory and antioxidant properties. Therefore, we propose to retrospectively analyze the effect of pre-operative TZDs on the incidence of post-operative AF or Aflut. This study will involve retrospective chart reviews without further patient contact of all patients having undergone cardiac surgery in Emory University Hospital, Crawford Long Hospital, or the VA Medical Center from 2000 to 2005. This study is preparatory to a funding proposal for a prospective trial.