Abstract
A four month-old intact female Maltese (weighing 1.8 kg) was present with major complaints of severe coughing and dyspnea. Diagnostic imaging studies revealed abnormally elongated chordae tendineae attached to anterior leaflet and shortened chordae tendineae attached to posterior leaflet of mitral valve causing mitral insufficiency and regurgitant blood flow into left atrium, indicating congenital mitral valve dysplasia. Therapy was directed to control existing clinical signs and to prevent further deterioration of cardiac enlargement using conventional cardiac medications. The dog is currently survived and being monitored at regular interval. This is the first case report describing mitral valve dysplasia causing mitral insufficiency of dog in Korea.