The relation of color m-mode flow propagation with cardiac iron load in patients with thalassemia major

Abstract

Myocardial iron overload remains an important problem and results in cardiac dysfunction in patients with thalassemia major (TM). The ratio of color M-mode flow propagation velocity to early diastolic transmitral flow velocity (E/Vp) in echocardiography is a marker of increased left ventricular filling pressure, which is independent of preload, afterload, and heart rate. We examined the relationship between E/Vp and iron loading in patients with TM using cardiac magnetic resonance imaging (MRI). Twenty-one TM patients and 21 age-matched healthy controls were enrolled in the study. Transmitral flow, pulmonary vein velocities, and Vp were obtained by two blinded echocardiographers. Left ventricular isovolumetric relaxation time (IVRT) was measured in the apical long axis by echocardiography. All patients also underwent MRI for cardiac T2* evaluation of iron overload. An increased E/Vp was defined as > 1.5. The E/Vp ratio was increased in TM patients compared with control subjects (1.7±0.4 and 1.2±0.2, P < 0.01, respectively). There was no correlation between E/Vp and cardiac T2* value. E/Vp was significantly correlated with IVRT (r=0.51, P = 0.02). In addition, the cardiac T2* value was comparable in patients with an E/Vp > 1.5 and E/Vp ≤1.5 (21.1±9.8 ms vs. 22.3±8.0 ms, P = 0.80, respectively). E/Vp may be a marker of diastolic abnormality that is independent from myocardial iron load in TM patients with preserved left ventricular function.