Unexplained fainting, near drowning and unusual seizures in childhood: screening for long QT syndrome in New Zealand families

Abstract

Aims: To construct detailed pedigrees of five New Zealand families with autosomal dominant long QT syndrome (LQTS) and screen selected individuals based on initial symptomatic and ECG data.

Methods: Clinical data were collected using a questionnaire and relevant medical record review. Participants were then classified according to ECG diagnostic criteria based on the presence or absence of symptoms and the rate-corrected QT interval (QTc) into three groups: affected, uncertain or unaffected. Blood samples were also collected from each participant and DNA extracted for genetic testing.

Results: Seventy-eight family members were screened. The majority of the 35 symptomatic family members, who were affected on these criteria, had presented with symptoms in childhood. Of the remaining 43 asymptomatic family members, the majority were in the uncertain diagnostic group based on these ECG criteria.

Conclusions: Autosomal dominant long QT syndrome (Romano Ward syndrome) is being increasingly recognised and must be considered in the investigation of children who present with unexplained fainting, near drowning, unusual seizures and sudden death. Screening long QT syndrome families based on ECG criteria remains difficult leaving a number of family members with an uncertain diagnosis. It is hoped that genetic testing will become useful for diagnosis of presymptomatic carriers of long QT syndrome in New Zealand in the future.