PRECLINICAL CARDIAC DYSFUNCTION IN TRANSFUSION-DEPENDENT CHILDREN ANDYOUNG-ADULTS DETECTED WITH LOW-DOSE DOBUTAMINE STRESS ECHOCARDIOGRAPHY

Transfusion-dependent (TD) patients develop cardiac iron overload that will eventually lead to cardiac pump failure. Low-dose dobutamine str ess echocardiography may complement resting echocardiography and ident ify preclinical myocardial dysfunction caused by early cardiac hemosid erosis. Twenty-six iron-overloaded TD patients had stress echocardiogr aphy with 5 mu g/kg per minute of dobutamine. Indexed left ventricular (LV) mass, LV dimensions, meridional wall stress, and cardiac index w ere significantly increased. TD patients had similar LV shortening fra ction by M-mode (40.5% +/- 5.6% vs 39.4% +/- 4.5%) but had a lower mea n LV ejection fraction (53.3% +/- 3.9% vs 46.8% +/- 6.9%, P < .002) an d a subnormal increase in cardiac index during dobutamine stress (35% +/- 20% vs 11% +/- 16%, P < .0001). Impairment in LV relaxation was de monstrated by a prolonged isovolumetric relaxation time (0.060 +/- 0.0 05 vs 0.088 +/- 0.019 seconds, P < .0001), increased peak mitral E wav e, and abnormal E/A ratio. Asymptomatic TD patients demonstrate decrea sed systolic functional reserve and abnormal left ventricular relaxati on that may be caused by cardiac hemosiderosis. Low-dose dobutamine st ress echocardiography may be useful for detecting and following cardia c dysfunction in patients at risk for cardiac hemosiderosis.