The occurrence and the pathogenesis of cardiac hypertrophy in Graves' disease

Abstract

1. 1. A study was made of the occurrence and pathogenesis of cardiac hypertrophy in 27 fatal cases of Graves' disease, in which the hearts were studied anatomically. A heart was considered hypertrophied if its weight exceeded Smith's standard of maximum normal heart weight for a given body weight and sex. In a few cases in which body weights were not available, a heart was considered hypertrophied if it exceeded Walmsley's maximum for the mean range of normal heart weights. 2. 2. Among these twenty-seven cases cardiac hypertrophy was found present in fourteen (52 per cent) and absent in thirteen. 3. 3. The six hearts showing the greatest degree of hypertrophy (40 to 122 per cent increase in heart weight) occurred in patients with wellmarked right heart failure, associated in some cases with hypertension, severe coronary sclerosis and narrowing, or established auricular fibrillation. In two other cases with moderate cardiac hypertrophy there was essential hypertension without cardiac failure. Two other patients with slight or uncertain hypertrophy had suffered from established auricular fibrillation and in one of these there was also severe coronary sclerosis. 4. 4. Only four of the twenty-seven cases of Graves' disease (14 per cent) showed cardiac hypertrophy independent of cardiac failure, essential hypertension or auricular fibrillation. In two of these there was marked coronary sclerosis. These cases showed the mildest degree of cardiac hypertrophy. Thus only two cases (7 per cent) showed cardiac hypertrophy (of very slight degree) independent of the various pathological states just mentioned. 5. 5. A study of the literature reveals an almost general agreement that cardiac enlargement or hypertrophy occurs in from 30 to 50 per cent of the cases. The implication in these reports is that the cardiac enlargement is a direct consequence of Graves' disease, but no adequate explanation is provided as to why cardiac enlargement is not invariably present, or what specific factors determine the occurrence of enlargement in some cases but not in others. Considering only the autopsied cases, it is evident that where specific case reports are available, such hypertrophy occurred almost invariably in association with cardiac failure, essential hypertension, auricular fibrillation or severe coronary artery disease. 6. 6. The commonest explanation of cardiac hypertrophy in Graves' disease is that it results from the increased work of the heart as indicated by increased cardiac output. It is pointed out, however, that increased cardiac output in Graves' disease is almost always due to tachycardia alone, while the systolic output almost invariably is not elevated. Since dilatation and hypertrophy depend on the increased diastolic tension which would be translated into increased systolic output, there should theoretically be no significant hypertrophy in uncomplicated cases of Graves' disease. 7. 7. The relationship of cardiac failure, hypertension, and auricular fibrillation to cardiac hypertrophy is discussed. 8. 8. It is concluded that cardiac hypertrophy in uncomplicated Graves' disease is quite uncommon and is of slight degree. When present in a given case it indicates that the increased cardiac output in that case was effected not only by tachycardia but also by an increased systolic output.