Atrial Arrhythmia and Bradycardia as a Presentation of Congenital Long QT Syndrome.

ABSTRACT

We present a term newborn with atrial arrhythmia on the first day of life (DOL). An echocardiogram showed normal structure and normal function; laboratory testing showed normal electrolytes and thyroid function. After initiation of flecainide, the EKG on DOL 2 showed significant and increasing bradycardia with atrial arrhythmia and extremely prolonged QTc interval. Flecainide was stopped and esmolol started. After 6 h of treatment, atrial tachycardia was suppressed, and the rhythm converted to sinus. Genetic testing found variants of unknown significance in the ALPK3 gene and KCNQ1 gene, which has been associated with long QT syndrome (LQTs). LQTs in infants can present as bradycardia, 21 AV block, or torsades de pointes. Our review of the literature found only one other case report of atrial arrhythmia in a newborn with congenital LQTs. Diagnosis of LQTs via EKG alone is difficult in neonates since the ST segment and T wave on the first DOL are usually flattened, making correct measurement of the QTc interval difficult. ß-blockers, the first line of treatment for LQTs, are known to shorten QTc intervals and prevent arrhythmia events. As in our patient, ß-blockers may be helpful for atrial arrhythmia prevention in patients with adrenergically mediated atrial tachycardia. In conclusion, atrial arrhythmia with bradycardia can be a presentation of congenital LQTs and be difficult to recognize. For neonates with this presentation with no evidence of myocarditis, congenital heart disease, or significant respiratory illness, genetic congenital LQTs should be highly suspected, especially when associated with low resting heart rates.