A 4 year old infact male Neopolitan Mastiff presented for evaluation of ascites, an irregularly irregular heart beat and a grade III/IV left-sided systolic murmur. Transthoracic echocardiography revealed severe dilation of all four heart chambers with poor contractility. In addition, Doppler and color flow echocardiography revealed moderate mitral insufficiency and mild to moderate tricuspid regurgitation. Medical therapy was initiated to control the clinical signs associated with congestive heart failure and consecutive 24 hour Holter monitors were used to modify the drug protocol.