Electrocardiographic abnormalities and arrhythmic risk markers in adult patients with beta thalassemia major.

BACKGROUND: There seems to be a significant arrhythmia burden in β-thalassemia major (TM) patients without overt cardiomyopathy. Apart from conventional electrocardiographic (ECG) and arrhythmic risk markers we studied novel markers of ventricular repolarization and autonomic imbalance both at rest and after exercise testing.

METHODS: We studied 47 adult TM patients without systolic heart failure and 47 age and sex-matched healthy control subjects. The median age of the studied population was 36 [32-43] years, 57% men. Baseline demographic and clinical characteristics were recorded while 12-lead electrocardiograms, 24-hour ECG Holter recordings, and treadmill exercise stress tests were analyzed.

RESULTS: TM patients exhibited increased QTc intervals in both 12-lead ECG recordings and in 24-hour Holter recordings. In addition, they had increased indexes of ventricular repolarization heterogeneity such as QT dispersion, and T peak-to-end/QT ratios. Furthermore, TM patients had decreased indexes of heart rate variability while the heart rate recovery after exercise was significantly attenuated compared to controls. Also, they had increased P wave and QRS duration while the QRS fragmentation was very prevalent. Finally, premature atrial extrasystoles and paroxysmal atrial fibrillation episodes were more frequent in TM patients.

CONCLUSIONS: TM patients with preserved left ventricular systolic function have several ECG abnormalities including alterations in ventricular depolarization and repolarization. Also, cardiac autonomic dysfunction is evident in 24-hour ECG monitoring as well as in the recovery phase after exercise testing. The prognostic value of specific arrhythmic risk indexes in this setting remains to be elucidated.