"Simba" a 6 year old, male castrated, domestic short hair presented to the Emergency Service at the Cornell University Hospital for Animals for syncopal episodes on May 25th of 2003. On presentation, Simba had a heart rate of 53 beats per minute with electrocardiographic evidence of third degree heart block. Echocardiography revealed generalized cardiac chamber enlargement with mild bivalvular regurgitation. Emergency surgery to place a pacemaker was performed to resolve Simba's clinical signs. Atrioventricular (AV) node dysfunction is rare in the cat and has been associated with neoplasia, cardiomyopathy and hyperthyroidism. The focus of this paper is to highlight the clinical presentation of a cat with AV node dysfunction as well as a brief introduction to pacemaker therapy.