Symptomatic sinus bradycardia in infants with structurally normal hearts.

Sixteen infants, ages 6 weeks to 23 months, were evaluated because of syncopal attacks (n = 6), apneic episodes (n = 3), or a combination of syncope, apnea, or "convulsions" (n = 7). Comprehensive metabolic and neurologic investigations yielded negative results in 15 infants; in one, an abnormal EEG was recorded. Severe sinus bradycardia, complete sinus arrest, junctional escape rhythm, or ventricular escape rhythm was found in four patients, and permanent multiprogrammable pacemakers were implanted. Follow-up for 6 to 24 months with ventricular demand pacing showed complete cessation of attacks in two infants and marked improvement in two.