Developmental aspects of long QT syndrome type 3 and Brugada syndrome on the basis of a single SCN5A mutation in childhood.
OBJECTIVE
The aim was to investigate at what age electrocardiographic characteristics of long QT syndrome type 3 (LQT3) and Brugada syndrome (BS), based on a single SNC5A mutation, appear.


BACKGROUND
The QT interval (QT) in LQT3 is prolonged during bradycardia. It is not clear yet if this is obvious in young children with a relative fast heart rate (HR).


METHODS
Thirty-six children with an SNC5A gene mutation (1795insD) and 46 non-carrier siblings were investigated. In different age groups, HR, QT, QTc, and ST-segment elevation on a 12-lead electrocardiogram (ECG), and HR, QT, QTc, and DeltaQT after the longest pause in a Holter (recording) were evaluated.


RESULTS
In all age groups, HR at rest tended to be lower in carriers than in non-carriers, and QT was longer in carriers than in non-carriers. The Brugada phenotype was found >5 years. Gender specific differences were not identified. The QT at lower HR and DeltaQT were longer in carriers than in non-carriers. A QTc of > or =0.44 s at the lowest HR (sensitivity 100%; specificity 88.4%) and DeltaQT > or =60 ms (sensitivity 100%; specificity 82.6%) were good predictors for having LQT3.


CONCLUSIONS
We conclude that electrocardiographic characteristics of LQT3 and BS show age-dependent penetrance. A QT prolongation and conduction disease were present from birth onwards, whereas ST-segment elevation only developed >5 years. Good tools for clinical diagnosis of LQT3 in this family are QTc at the lowest HR and DeltaQT after a pause in a Holter, even at very young age.
Beaufort-Krol
Gertie C M
GC
Beatrix Children's Hospital, Department of Pediatric Cardiology, Groningen, the Netherlands.
van den Berg
Maarten P
MP
Wilde
Arthur A M
AA
van Tintelen
J Peter
JP
Viersma
Jan Willem
JW
Bezzina
Connie R
CR
Bink-Boelkens
Margreet Th E
MT
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D002037:Bundle-Branch Block / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D016757:Death, Sudden, Cardiac; D004562:Electrocardiography; D015716:Electrocardiography, Ambulatory; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006579:Heterozygote; D006801:Humans; D007223:Infant; D008133:Long QT Syndrome / Q000235:genetics*; D008297:Male; D009154:Mutation; D062554:NAV1.5 Voltage-Gated Sodium Channel; D010375:Pedigree; D010641:Phenotype; D012306:Risk; D012680:Sensitivity and Specificity; D015222:Sodium Channels / Q000235:genetics*
D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human; D015222:Sodium Channels