[Neonatal forms of congenital long QT syndrome]

The neonatal congenital long QT syndrome (LQTS) is rare and of bad prognosis due to the presence of severe ventricular arrhythmia and conduction abnormalities.

we included 24 propositus newborns from our population with LQTS. Genetic study was possible in 19 cases.

the diagnosis of LQTS was made according to a QT prolongation associated with a sinusal neonatal bradycardia (n=9) or a 2/1 AV block (n=15). The onset presentation consisted of syncope (n=2), torsades de pointes (n=7), cardiovascular collapse (n=5), cardiac arrest (n=1). The mean QTc was at 550+60 ms. During the neonatal period the treatment consisted of beta-blocking agents in all cases, associated with a definitive pacemaker implantation in 10 cases with 2/1 AV block. Three newborns with a 2/1 AV block died during the first month of life (one case due to a septecemia after implantation of a pacemaker, and two who were waiting for that implantation). All survivors remained asymptomatic during a follow-up period of 7 years. In all cases with a 2/1 AV block we identified mutations in HERG (n=8). Newborns with isolated sinusal bradycardia presented all a mutation in KCNQ1 (n=9).

the LTQS with 2/1 AV block is preferably associated with mutation in HERO with a bad initial prognosis.