Prevalence of idiopathic long QT syndrome in congenital sensori-neural hearing loss students of Songkhla School for the Deaf.

ABSTRACT

OBJECTIVES: To survey the prevalence of the long QT syndrome (LQTS), especially Jervell-Lange-Nielsen syndrome (JLNS), in Thai children (The first such study). BACKGROUND: LQTS is a rare inherited disease with a prevalence of 0.21 per cent in children with congenital deafness from other reports. These patients carry a high risk of recurrent syncope and fatal ventricular arrhythmia. STUDY DESIGN: Cross-sectional survey from January 2000 to August 2000. METHOD: A total of 276 children with congenital sensori-neural hearing loss were included. A questionnaire was employed and all children were examined by a pediatric cardiologist to rule out organic heart disease. EKGs were obtained and QTc intervals were blindly measured using standard methods in L2, V5 or any other leads with the longest QTc interval by three pediatric cardiologists. If QTc interval is prolonged, additional EKG (up to 3) were done to confirm the finding. Schwartz criteria was used to identify index cases with LQTS after repeated EKGs, and exercise stress tests. Also, echocardiography were done in patients suspected of having LQTS. RESULTS: A total of 14 children needed a third EKG and more work ups due to persistent long QTc interval after 2 consecutive EKG studies with QTc intervals ranged from 456 msec to 466 msec, and Schwartz score from 1.5 to 2.5. There were 6 twins and no triplets in the study. Finally, two subjects (not twins or siblings) had persistent prolonged QTc intervals after 3 EKG studies. After the exercise stress test, both still had a prolonged QTc interval, not corrected to the normal QTc interval even at the exercise peak. There was no cardiac abnormality either structurally or functionally from the 2D echocardiogram and Doppler color flow study. CONCLUSION: The possible prevalence of JLNS was 0.7 per cent (2/276). Both children were in the low-risk group for having LQTS.