• R E Tanel, J K Triedman, E P Walsh, M R Epstein, J M DeLucca, J E Mayer, S B Fishberger, and J P Saul.
• Department of Cardiology, Children's Hospital, Boston, Massachusetts 02115, USA.
• J. Cardiovasc. Electrophysiol. 1997 Jul 1;8(7):812-7.

IntroductionThe neonatal presentation of the long QT syndrome is rare, although it is frequently accompanied by life-threatening arrhythmias. Infants may not survive childhood despite traditional management with beta-adrenergic blockade and pacing.Methods And ResultsThis case describes a newborn with a long QT interval, T wave alternans, intermittent 2:1 AV block, ventricular arrhythmias, and a family history of sudden death. After failing medical therapy, conventional VVI and DDD pacing were unsuccessful due to prolonged ventricular refractoriness and proarrhythmia. At 2 months of life, the child was treated with high-rate (180 ppm) atrial pacing to produce intentional 2:1 AV block. Following an episode of possible syncope at 16 months of age, an automatic implantable cardioverter defibrillator (ICD) was added. Finally, as recently reported, acutely induced hyperkalemia led to both a marked decrease in QTc and functional improvement in repolarization (consistent 1:1 AV conduction at rates to 180 beats/min). Spironolactone and dietary potassium were added and have produced the same effects chronically.ConclusionsHigh-rate atrial pacing with 2:1 AV block is presented as a novel and "bridging" therapy for neonatal long QT syndrome and 2:1 AV block with ventricular arrhythmias. Definitive therapy with ICD implantation was then possible when patient size was substantially increased. The electrophysiologic response to intentional elevation of the serum potassium suggests a genetic defect in an inward potassium channel and demonstrates a possible therapy of long QT syndrome in some future patients.

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