Left Ventricular Rotational Dynamics in Beta Thalassemia Major: A Speckle-Tracking Echocardiographic Study

Abstract

Iron-mediated cardiomyopathy is the leading cause of death in patients with thalassemia major (TM). The identification of subclinical cardiac involvement in the early phases of the disease is important to optimize therapeutic strategies. The aim of this study was to identify early markers of cardiac dysfunction through new parameters of cardiac rotational dynamics and to look for a relationship with parameters of iron overload. Twenty-seven asymptomatic patients with TM and 27 healthy control subjects were prospectively enrolled. All subjects underwent standard echocardiography and subsequent offline analysis to assess left ventricular (LV) rotation and longitudinal mechanics using speckle-tracking echocardiography. In all patients with TM, ferritin levels were measured, and a subgroup underwent cardiac magnetic resonance imaging. All subjects had normal parameters of cardiac function, although patients with TM showed significantly lower S' values (P= .030) and E' values (P= .025), with increased E/E' ratio (P= .003) and indexed left atrial volumes (P= .022). Compared with controls, patients with TM had significantly reduced systolic apical rotation (P= .006), LV twist (P= .002), and LV torsion (P= .001). Systolic and diastolic rotational peak velocities at the apical level were also significantly decreased in the TM group (P= .003 and P= .011, respectively) with reductions of twisting and untwisting rates (P= .003 and P= .001, respectively). Patients with TM also showed a significant reduction of longitudinal displacement from the two-chamber apical view (P= .042) but preserved longitudinal strain and strain rate. Patients with T2* values > 20 msec had preserved rotational function, while those with T2* values < 20 msec showed significantly lower mean values of LV peak basal systolic rotation (-3.1 ± 1.4° vs -6.2 ± 2.6°, P= .016), LV peak apical systolic rotation (3.4 ± 1.3° vs 6.4 ± 3.1°, P= .045), LV twist (4.8 ± 2.5° vs 10.9 ± 4.9°, P= .012), and LV torsion (0.6 ± 0.2°/cm vs 1.4 ± 1.6°/cm, P= .010). LV torsion was negatively related to ferritin levels (r= -0.47, P= .013) and directly to T2* values (r= 0.64, P= .007). LV rotational dynamics in asymptomatic patients with TM are negatively related to iron overload. Rotational function of the left ventricle is preserved in patients with normal T2* values. These new parameters are useful for an early diagnosis of cardiac involvement.