Background

Long QT syndrome (LQTS) occurs in about 1 in 2500 of the general population.1 Of the 12 genotypes, LQTS type 1 is the most common type and is classically associated with exercise-related events, especially swimming,2 and the QT interval prolongs with Epinephrine infusion3 and after exercise.4 Mutations are in KCNQ1 and the cardiac potassium channel I_Ks is defective, such that the action potential is prolonged.5 6 Of the first 388 index cases with LQTS at the Mayo clinic, 28 (11%) had a history of swimming triggered events; 85% of these were due to LQTS type 1, 6% to LQTS type 2 and 3% were genotype negative.7

The relationship of drowning and near drowning to LQTS is well established. However, the nature and outcome of these events are not well described in children. It is essential to have a high index of suspicion when faced with these cases in order to make a prompt diagnosis and prevent unnecessary mortality and morbidity in these children, and take the opportunity to find and protect undiagnosed family members. We recently found that one third of a group of unrelated probands diagnosed with LQTS were initially misdiagnosed as having a seizure disorder, resulting in years of inappropriate treatments.8 During these years of delay (a mean of 9 years in those treated as epileptic), there were a number of sudden deaths in family members which might have been prevented. With this in mind we aimed to review the details of presentation and outcome, and time to final diagnosis, of children with LQTS who presented with a syncopal event related to water.