Low incidence of cardiac events with beta-blocking therapy in children with long QT syndrome.

AIMS: To evaluate the effect of beta-blockers in children with long QT syndrome (LQTS) we reviewed the outcome of 122 patients (pts).
METHODS: LQTS was diagnosed in 24 neonates and in 98 pts aged 0.5-15 years. Diagnosis was made because of syncope in 51 pts, bradycardia in 10 neonates and family history in 61 pts. The longest QTc ranged from 400 to 700 ms. Thirteen pts had 2:1 atrioventricular block and/or ventricular arrhythmias. Screening for mutations was performed in 118 pts. All children were treated with beta-blockers, annually checked by exercise testing and/or 24 h ECG monitoring.
RESULTS: Four pts died. Survivors were followed-up for 1-18 years (7.5 +/- 5.3 years). Five neonates and 3 older pts received a prophylactic pacemaker (1 death) so that only 111/122 pts survived and were followed-up with beta-blockers alone. None of them died and five experienced a non-fatal cardiac event. There was no cardiac event among pts who were diagnosed because of familial history and among symptomatic KCNQ1 pts who were effectively treated with beta-blockers.
CONCLUSION: The outcome of children with LQTS under effective beta-blockers is favourable. Persisting arrhythmia or symptoms despite beta-blockers should aim at identifying other genotypes than KCNQ1.