Isolated sinus node dysfunction in an infant with developmental delay.

We present a case of an infant with developmental delay, a structurally normal heart, and prolonged sinus pauses that suffered an unmonitored cardiac arrest while in the hospital. An investigation into the etiology of her sinus pauses did not reveal a definitive cause, and she continued to have pauses up to 15 s in duration. Her history of the cardiac arrest and the duration of the pauses guided the physicians' recommendations and the family's decision to undergo pacemaker implantation prior to discharge from the hospital.