A 4 year old mixed female dog was presented dyspnea, anorexia and syncope. In blood smear test, a lot of heartworm larvae were observed. In thoracic radiography, "reverse D" shape was observed. So, this case was considered with heartworm disease. In echocardiography, marked left heart hypertrophy was presented. In M-mode view, aortic valvular stenosis was found. After mongrel dog died, aortic valvular stenosis was reconfirmed in necropsy. After all, the dog died of pulmonary edema because of aortic valvular stenosis caused left heart failure.t failure.