The Role of Heart Rate Variability and Fragmented QRS for Determination of Subclinical Cardiac Involvement in Beta-Thalassemia Major.

Background: Iron accumulation leads to increased susceptibility to cardiovascular diseases in thalassemia major (TM) patients. Depressed heart rate variability (HRV) and development of arrhythmia are among the manifestations of subclinical cardiac involvement in TM cases. Determination of subclinical cardiac involvement is essential for preventive measures. Thus, we aimed to evaluate the best method for identification of subclinical cardiac dysfunction in TM cases.

Materials and Methods: In this prospective study, 45 TM and 45 non-TM cases, who were referred for cardiac evaluation, were enrolled. Exclusion criteria included non-sinus rhythm and overt cardiac disease. TM cases underwent cardiac MRI, electrocardiography (ECG), and Holter monitoring. TM cases were divided into two groups of normal versus iron overload with a cardiac T2* of more or less than 20 ms, respectively. The non-TM cases underwent only ECG and Holter monitoring.

Results: We observed no significant difference regarding HRV between normal versus iron overload TM and non-TM cases. Higher rates of premature atrial complex, low limb voltage, low atrial rhythm, as well as minimum and average HR with lower QRS duration and PR interval were detected in TM versus non-TM cases ( p value <0.05).

Conclusions: We observed a higher prevalence of low limb voltage and low atrial rhythm in TM cases versus non-TM cases. Indeed, the role of fragmented QRS (fQRS) for subclinical detection of cardiac disease in TM cases is still so controversial and needs more evaluation. Application of HRV and fQRS in this regard may need to be performed at the right time point after initiation of blood transfusion, but this needs to be determined.