Concurrent incomplete atrioventricular septal defect and supravalvular mitral stenosis causing heart failure in a 13-year-old cat: a case report

A 13-year-old female Persian cat with a heart murmur presented with dyspnea. Thoracic radiography revealed pleural effusion and dilation of peripheral pulmonary vessels. Echocardiography showed significant enlargement of the right atrium and ventricle and left atrial appendage; an atrial septal defect (ASD) near the atrioventricular valves; and a septum-like structure below the left atrial appendage. Left-to-right shunting through the ASD was noted, with a pulmonary-to-systemic flow ratio of 2.72. The cat was diagnosed with incomplete atrioventricular septal defect (IAVSD) and supravalvular mitral stenosis (SVMS) and subsequently medically managed for 7 months before death. Necropsy confirmed IAVSD with a mitral valve cleft and SVMS. To our knowledge, this is the longest reported survival in a cat with both anomalies.