Two:One atrioventricular block in infants with congenital long QT syndrome

Abstract

Congenital prolongation of the QT interval is a rare but life-threatening disorder of the cardiac conduction system.1-5 The disorder usually presents as syncope or sudden death due to complex polymorphic ventricular tachycardia (torsade de pointes) or ventricular fibrillation.6 The major hypothesis explaining the disorder is an imbalance of sympathetic discharge between the right and left stellate ganglia resulting in inhomogeneity of ventricular refractoriness and a substrate for reentrant ventricular arrhythmias.4-6 Although sinus bradycardia may be associated with the syndrome, abnormalities in atrioventricular (AV) conduction are rare.4 In this report we present 3 infants with the congenital long QT syndrome and 2:1 AV block and provide support for the role of the long effective refractory period in producing the block.