High-rate atrial pacing as an innovative bridging therapy in a neonate with congenital long QT syndrome.
BACKGROUND
The 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.


RESULTS
This 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.


CONCLUSIONS
High-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.
Tanel
R E
RE
Department of Cardiology, Children's Hospital, Boston, Massachusetts 02115, USA.
Triedman
J K
JK
Walsh
E P
EP
Epstein
M R
MR
DeLucca
J M
JM
Mayer
J E
JE
Fishberger
S B
SB
Saul
J P
JP
D001145:Arrhythmias, Cardiac / Q000473:pathology / Q000628:therapy; D002304:Cardiac Pacing, Artificial; D017147:Defibrillators, Implantable; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008133:Long QT Syndrome / Q000151:congenital / Q000628:therapy*