Doppler characterization of left ventricular diastolic function in beta-thalassaemia major. Evidence for an early stage of impaired relaxation.

Abstract

Doppler echocardiographic studies of left ventricular diastolic function in patients with thalassaemia major have shown conflicting findings. This study was undertaken to compare Doppler echocardiographic parameters of diastolic function among a group of patients with thalassaemia major, a group with thalassaemia intermedia and a group of normal individuals. 50 patients with thalassaemia major, 38 patients with thalassaemia intermedia and 29 normal subjects were studied. All had normal systolic function. The thalassaemia intermedia patients had larger body surface area and left ventricular mass index than the thalassaemia major patients but less than the controls. The ratios between peak early and late mitral diastolic flow (E/A ratio) were comparable between the three groups. The haematocrit levels were comparable in the two study groups, but the ferritin levels were significantly higher in the thalassaemia major group (P<0.001). Using multiple regression analysis to correct for the influence of heart rate, age and body surface area, we found a prolonged isovolumic relaxation time (P<0.03) and a lower E wave (P<0.001) in the thalassaemia major group as compared to the thalassaemia intermedia group. The isovolumic relaxation time also differed significantly between the thalassaemia groups and the control (P<0.001), suggesting a state of impaired relaxation most notable in thalassaemia major that is probably due to iron overload. In patients with thalassaemia major and normal systolic function who have iron overload, the earliest sign of diastolic dysfunction is an impairment in left ventricular relaxation manifested as a prolonged isovolumic relaxation time.