Background: Iron induced cardiac abnormalities remain the number one cause of death among thalassemia major (TM) patients. Signal averaged ECG (SAECG) was suggested to predict ventricular tachycardia as the underlying substrate for up to 5% incidence of sudden cardiac death among TM patients. The prevalence of ventricular late potentials (VLP) among different TM populations varied (3-31%); therefore to further clarify this we here describe the incidence of VLP among TM patients over a 7 year follow up period (1997 to 2004).
Methods: 26 TM patients were randomly selected from a group of 240 TM patients. SAECG, regular ECG, echocardiography-Doppler were analyzed during the study period. Ferritin levels and cardiac complaints were registered from an interview and chart review.
Results: Mean QRS duration increased from 89.23 (+/-10.60) ms in 1997 to 94.27 (+/-10.91) in 2004 (p<0.01), mean late amplitude signal (LAS) duration increased from 23.04 (+/-7.68) ms in 1997 to 27.69 (+/-6.82) ms in 2004 (p=0.01), whereas mean root mean square voltage RMS decreased from 80.85 (+/-51.19) mV in 1997 to 45.12 (+/-21.42) mV in 2004 (p<0.01). Changes in QRS duration and RMS voltage were found to be linearly correlated with average of ferritin over years (r=0.38, p=0.03 and r=-0.47, p=0.01 respectively); and only 1 patient developed VLP over 7 years.
Conclusion: The incidence of VLP is 3.8% in the TM population over 7 years, despite the presence of significant changes in all SAECG criteria. RMS voltage and QRS duration changes over time seem to be related to iron overload measured by ferritin level.