ROLE OF CARDIAC IMAGING IN EARLY DIAGNOSIS OF β-THALASSEMIA MAJOR’S IRON OVERLOAD CARDIOMYOPATHY

BACKGROUND: Iron overload cardiomyopathy (IOC) results from the accumulation of iron in the myocardium, and it is the leading cause of death in patients receiving chronic blood transfusion therapy like patients with thalassemia major (TM). It has been documented that adequate medical therapy can reverse IOC when it is diagnosed before end-stage heart failure occurs, thus underscoring the importance of early detection of IOC, in which speckle tracking echocardiography (STE) can play an important role. METHODS: 154 patients from a primary thalassemia unit were screened and after applying the exclusion criteria, 41 patients affected by TM, receiving long-term blood transfusions every 3 weeks and undergoing iron chelation therapy were prospectively enrolled. 41 healthy subjects, age and sex matched, were included as control group. Both TM patients and control group underwent STE and offline software analysis. T2* CMR exam in a single center was performed in the TM group to assess the myocardial iron overload. RESULTS: Although average values were within normal range, patients with TM had significantly higher LVEDD, LV mass, LVMi, LA volume, mitral and tricuspidal A velocity, EDT, systolic pulmonary artery pressure (PAPs), septum Sm, and lower EF, LVEDV, LVESV, mitral and tricuspid E/A ratio and IVRT. The LV circumferential systolic strain was similar between groups , excepting the anterior and infero-septal walls (p=0.001 and 0.003 respectively), while longitudinal and radial systolic strain was different between controls and TM patients, being lower in the thalassemia group, almost for all segments of the left ventricle. Regarding strain rate (SR), when comparing the groups, the major difference was between radial SR at the level of the antero-septal, infero-lateral and antero-lateral walls (p=0.033, respectively 0.01 and 0.035). The cardiac T2* correlated only with radial SR at the level of the infero-septal wall (p=0.009). The EF and FS measured with echo and CMR correlates well with T2* (p=0.001 and 0.002 for echo, respectively 0.026 and 0.007 for CMR). The longitudinal and circumferential global systolic strain was similar between control and thalassemic group (20.06+/-1.53% vs. 20.8+/-2.66%, p=0.09 and 19.9+/-2.08% vs. 18.96+/-2.72%, p=0.11) while radial global systolic strain was significantly lower in thalassemic patients (27.9+/-4.53% vs. 21.5+/-7.9%, p<0.001). CONCLUSIONS: IOC is a potentially lethal, but treatable disease when diagnosed and treated early in its course. Iron studies, cardiac MRI with T2* measurement, echocardiographic assessment, and plasma BNP levels are all important diagnostic and prognostic tools to evaluate patients with iron-overload cardiomyopathy. Once heart failure develops, the prognosis is usually poor with precipitous deterioration and death, despite intensive chelation. Conventional echo parameters do not provide enough informations for early ventricular dysfunction. 2D strain imaging is one of the latest techniques and may provide additional data for management of thalassemic patients suspected of iron cardiomyopathy. The major advantage of 2D strain over conventional echo parameters is its superiority in detecting the subclinical cardiac involvement and the fact that is not affected by age and volume load and being not angle-dependent.