[An autopsy case of elderly idiopathic enlargement of the right atrium]

We report an autopsy case of an 88-year-old man with idiopathic enlargement of the right atrium which is considered to be the oldest case reported. The patient was given a diagnosis of atrial fibrillation at the age of 75 years, when he developed congestive heart failure. Bradycardia associated with partial atrial standstill was detected and, the patient underwent implantation of a pacemaker at age 77. An echocardiogram revealed marked enlargement of the right atrium and moderate enlargement of the left atrium. Thus, idiopathic enlargement of the right atrium was diagnosed. He had recurrent congestive heart failure before admission to our hospital because of malnutrition and anemia. Although he was treated with high calorie intravenous infusion and blood transfusion, he died of pneumonia and heart failure. Postmortem examination revealed that the heart weighed 430 g, and there was marked dilatation of the right atrium which had an extremely thin wall. The annular circumference of the tricuspid valve was markedly dilated, 170 mm, resulting in tricuspid regurgitation. The left atrium was moderately dilated and the right and left ventricles were slightly dilated. Histologically, the free wall of the right atrium was totally replaced by fibrous tissue and atrioventricular valves did not reveal any rheumatic changes. These pathological findings were compatible with idiopathic enlargement of the right atrium. There has been no previous case report of idiopathic enlargement of the right atrium in a patient aged 80 years of age or over.