Congenital long QT syndrome and 2:1 atrioventricular block: an optimistic outcome in the current era.

Background: Previous studies of patients with long QT syndrome (LQTS) and 2:1 atrioventricular block (AVB) have reported a mortality rate greater than 50% during infancy.

Objective: The purpose of this study was to determine the outcome of this high-risk population in the current era.

Methods: A retrospective study from four tertiary care pediatric centers assessed patients with congenital LQTS and 2:1 AVB from January 2000 to January 2009. All neonates who presented with 2:1 AVB and prolonged QTc unrelated to medication were included in the study. Statistical analysis was performed using a paired t-test. Medical records were reviewed for ECG findings, genotype, medications, and device therapy.

Results: Twelve patients that met the inclusion criteria were identified. All patients underwent diagnostic ECG in the first 24 hours of life. The average QTc interval prior to therapy was 616 +/- 99 ms (range 531-840 ms). Over a follow-up period of 71 +/- 45 months (range 15-158 months), 11 of 12 patients received devices (8 permanent pacemaker, 3 implantable cardioverter-defibrillator). Average age of device placement was 48 months (median 2 months, range 3 days to 10.5 years). All patients were treated with beta-blockers; mexiletine was added in three patients, and mexiletine and flecainide were added in one patient. Three (25%) patients experienced torsades de pointes while receiving beta-blockers, one of which was refractory to medical therapy. This patient underwent left cardiac sympathetic denervation and implantable cardioverter-defibrillator placement. Genotyping was available for 6 (50%) patients (2 SCN5A mutation, 4 KCNH2 mutation). At last follow-up, no mortality was observed. Follow-up QTc intervals had decreased (mean 480 +/- 20 ms, range 450-507 ms, P <.002).

Conclusion: Management of patients with LQTS and 2:1 AVB presents unique challenges. Despite historical data indicating poor prognosis, our study represents a cohort of high-risk LQTS patients with a relatively optimistic outcome. This finding reflects early diagnosis and intervention, coupled with improved management strategies, in the current era.