Myxoma of the left atrium.

Tumours of the heart are not common. Benjamin (1939) reports the incidence of primary tumours as 0 03 per cent of 40,000 autopsies. Nearly 50 per cent of these primary tumours are myxomata or myxomatous polyps. Yater (1931) (77 cases), Mahaim (1945) (82 cases) and Pritchard (1951) (125 cases) have collected and reported cases and the number reported is probably still less than 250. Approximately 75 per cent of myxomata occur in the left atrium, while almost all the remainder are found in the right atrium. Pritchard (1951) records one myxoma arising in the left ventricle and one from the mitral valve. Young and Hunter (1947) also report a left ventricular myxoma. During the past seven years, from 1951 to April 1958, some 600 operations for the relief of mitral stenosis have been performed at the Toronto General Hospital. Three cases, believed to have mitral stenosis and advised to undergo commissurotomy, were found at operation to have a myxoma of the left atrium. Similar errors in diagnosis have occurred at other centres (Belcher, 1958; Brock, 1956; Chin and Ross, 1957; Fatti and Reid, 1958; Horlick and Merriman, 1957; Likoff et al., 1954). In centres where angiocardiography is used extensively in investigating mitral valve disease, these tumours have been recognized on finding a filling defect of the left atrium (Goldberg et al., 1952; Steinberg et al., 1953; Marions and Odman, 1957). However, in this centre, if the clinical findings leave doubt as to the presence of mitral stenosis or its dominance in a mixed mitral lesion, left heart catheterization and dye injection studies (Gunton et al., 1958) have been found useful and angiocardiography has not been used. To avoid missing our three cases some 600 angiocardiograms would have been necessary. Routine angiocardiography would not therefore seem a practical solution. Thus it seems important to review the reported cases to see whether it is possible to distinguish myxomata from mitral stenosis by means other than angiocardiography.