Detection of early cardiac dysfunction in patients with severe beta-thalassemia and chronic iron overload.

To detect early left ventricular dysfunction, we used radionuclide cineangiography to determine left ventricular ejection fraction during exercise in 24 patients with transfusion-dependent, congenital anemias, 21 of whom had severe beta thalassemia. Ejection fraction at rest was normal in 21 patients (greater than 45 per cent) and in all patients was 53 +/- 2 per cent (mean +/- S.E.M.)--not significantly different from the value in normal subjects. However, ejection fraction during exercise was normal in only 11 patients (53 +/- 3 per cent in all patients, P less than 0.001 as compared with the normal value). All eight patients who had received fewer than 100 transfusions but only three of 16 (19 per cent, P less than 0.001) who had received 100 or more transfusions had normal responses during exercise. Whereas echocardiographic fractional shortening at rest was normal in 16 of 19 patients studied, eight patients with normal fractional shortening had abnormal ejection-fraction responses to exercise. Thus, radionuclide cineangiography during exercise is a highly sensitive technique for detecting preclinical myocardial dysfunction in patients with systemic iron overload.