Progression of Juvenile Atrial Standstill in a Boy with SCN5A Mutation

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Juvenile atrial standstill is a rare myocardial abnormality characterized by bradycardia, absence of P waves, and loss of the electrical activity of the atria. We experience a case with rapid progression of atrial standstill with SCN5A mutation in a child. The disease progression was confirmed by repeated electro-anatomical mapping (CARTO). A 12-year-old boy with sustained atrial flutter (AFL) without underlying heart diseases was referred to our hospital for catheter ablation. The AFL was diagnosed of common AFL by electrophysiological study and successfully treated by cavo-tricuspid ithmus (CTI) ablation. After ablation, continuous junctional rhythm and abcense of P wave were observed. CARTO showed electorically silent and unexcitable zone located in the posterior wall of right atrium (RA). CARTO voltage mapping one year after ablation showed that electrically silent zone was spread to the whole free wall and septal area in RA. VVI pacemaker implantation (PMI) was performed at 14 years old since atrial pacing with a maximum output didn’t capture the whole RA. After PMI, he had frequent atrial tachycardia episodes. CARTO performed at 17 years old couldn’t record electrical activities in any site of RA. Catheter ablation was not performed because atrial tachycardia was not inducible. Genetic screening revealed SCN5A-D1275N mutation but no connexin 40 mutation.