Severe sinus bradycardia in a patient with Rett syndrome: a new cause for a pause?

Rett syndrome is a progressive disorder seen primarily in young females. It is characterized by autonomic dysfunction affecting many organ systems. Although sudden death is common in these patients, little is known about the cardiovascular manifestations of this dysautonomia. Earlier reports focused on the role of sympathetic overactivity manifest as reduced heart rate variability and prolonged QT intervals indicating a propensity for lethal ventricular arrhythmias. Bradyarrhthmias and sinus node dysfunction, however, have not previously been reported. We describe a 2-year-old with Rett syndrome and severe sinus bradycardia requiring a pacemaker implant. This case represents the first description of a new cardiovascular manifestation of Rett syndrome and may provide an explanation for sudden and unexpected death in some of these patients.