Factors Associated with Cardiac Enlargement in Myxoedema.

Involvement of the heart in hypothyroidism (myxcedema heart disease) was first recorded by Zondek in 1918. Since then attention has been focused on the histological characteristics of the cardiac lesion and the clinical manifestations of myxcedema heart disease (Fahr, 1925; Campbell and Suzman, 1934; Means, 1937; Fournier, 1942; Bustamante et al., 1955; Hamilton and Greenwood, 1957). Myocardial damage (Hallock, 1933; Means, 1937; Ellis et al., 1952; Hamilton and Greenwood, 1957), pericardial effusion (Freeman, 1934; Marzullo and Franco, 1939; Boivin, 1945; Schnitzer and Gutmann, 1946; Kern et al., 1949), and premature coronary artery disease (Fishberg, 1924; Fahr, 1925) have all been shown to occur, but the incidence of these various lesions is still uncertain. This, no doubt, has in part been due to the relatively small number of patients studied in previous investigations. Radiological enlargement of the heart has also been said to be common in myxcedema, due either to myocardial damage (cardiomyopathy) or to the presence of a pericardial effusion or as a consequence of both of these lesions (Hallock, 1933; Freeman, 1934; Means, 1937, Scherf and Boyd, 1939; Schnitzer and Gutmann, 1946; Kern etal., 1949; Hamilton and Greenwood, 1957). Similarly, electrocardiographic evidence of myxcedema heart disease is reported as occurring in 70 to 80 per cent of patients with established myxcedema (Lerman, Clark, and Means, 1933; Bellet and McMillan, 1945; Hamilton and Greenwood, 1957). Such observations have led to the belief that radiological cardiac enlargement is an almost invariable accompaniment of obvious cardiographic evidence of myxcedema heart disease, whether or not there have been previous symptoms of cardiac embarrassment. This alleged relation, however, has never been proven. The present investigation was therefore designed to study some of the factors influencing heart size and the electrocardiogram in myxcedema.