Tissue Doppler Echocardiography in Detection of Myocardial Iron Overload Confirmed by Cardiac MRI in Patients With Beta Thalassemia Major: A Meta-Analysis

Abstract

Background: Myocardial iron overload is the most serious complication seen in transfusion-dependent beta thalassemia. Congestive heart failure remains to be the leading cause of death in thalassemia major patients. It is therefore important to facilitate early detection of myocardial iron overload in affected patients to avoid inevitable complications of treatment. Cardiac magnetic resonance imaging (MRI) continues to be the gold standard in detecting myocardial iron overload as it is the most sensitive and most precise imaging procedure available. It is however expensive, time-consuming and not universally available in all institutions. These reasons preclude it from being widely utilized in our practice. Tissue Doppler echocardiography on the other hand is widely available, faster and has significantly lower costs than the latter. These characteristics make it a promising alternative diagnostic tool for detection of and screening for cardiac iron overload. This study aims to determine the correlation of tissue Doppler echo parameters compared to the current gold standard, cardiac MRI T2 star. Methods: A literature search of published English language studies was performed using PubMed, MEDLINE and the Cochrane Collaboration from 1990 to 2013. Articles included were prospective cross-sectional and case-control trials. The risk of bias assessment (PRISMA) feature of Revman 5.0 and the QUADAS criteria were used to qualify for validity of the said qualified studies. Results: Five prospective observational studies were included with a total of 276 subjects. Four tissue Doppler parameters were analyzed and compared to cardiac MRI T2* findings. Results showed that patients with some degree of iron overload, evident in CMR T2* < 20 ms, had a statistically significant decrease in left ventricular ejection fraction (LVEF) with an overall mean difference (MD) of -3.84 (-5.85, -1.83) (Z = 3.75, P = 0.0002); increased Tei index (MD 13.03 (9.77, 16.99), Z = 7.83, P < 0.00001); and shorter deceleration times (MD -27.10 (-33.50, -20.71), Z = 8.31, P < 0.00001). There was no difference in E/A ratio of normal subjects versus iron overloaded patients (MD 0.18 (0.09, 0.27)) and therefore is not a reliable parameter to gauge myocardial iron overload (Z = 3.88, P = 0.0001). Conclusion: Tissue Doppler parameters that were seen to have good correlation with cardiac MRI T2*, the current gold standard, are Tei index, deceleration time and LVEF. J Hematol. 2014;3(1):1-9 doi: http://dx.doi.org/10.14740/jh107w