Abstract
A 8-year-old 11-kg female Bull Terrier was admitted for evaluation of a diastolic heart murmur. Echocardiography was performed and mitral stenosis diagnosed. A survey of thoracic radiographs revealed pulmonary edema. We used enarapril and trasemide for the initial treatment and cut only trasemide at 240 days. We performed open mitral commissurotomy under a cardio-pulmonary bypass at 492 days. After closing the heart，mitral inflow velocity was lower than it was preoperation. The dog was euthanatized because of signs of cerebral death. There was cartilage metaplasia and myxomatous degeneration of the mitral valve in pathological histology. This case indicates that early surgical treatment is necessary for difficult cases preserved by medical treatment and it is required to properly estimate the degree of mitral valve disorder and investigate the valvoplasty and valve replacement of the mitral valve.
