RT Journal Article SR Electronic T1 Long QT syndrome and life threatening arrhythmia in a newborn: molecular diagnosis and treatment response JF Heart JO Heart FD BMJ Publishing Group Ltd and British Cardiovascular Society SP 13 OP 16 DO 10.1136/heart.90.1.13 VO 90 IS 1 A1 Schulze-Bahr, E A1 Fenge, H A1 Etzrodt, D A1 Haverkamp, W A1 Mönnig, G A1 Wedekind, H A1 Breithardt, G A1 Kehl, H-G YR 2004 UL http://heart.bmj.com/content/90/1/13.abstract AB Intrauterine and neonatal manifestations of congenital long QT syndrome are associated with a high cardiac risk, particularly when atrioventricular block and excessive QT prolongation (> 600 ms1/2) are present. In a female newborn with these features, treatment with propranolol and mexiletine led to complete reduction of arrhythmia that was maintained 1.5 years later. High throughput genetic analysis found a sodium channel gene (LQT3) mutation. Disappearance of the 2:1 atrioventricular block and QTc shortening (from 740 ms1/2 to 480 ms1/2), however, was achieved when mexiletine was added to propranolol. This effect was considered to be possibly genotype related. Early onset forms of long QT syndrome may benefit from advanced genotyping.