Background: A routine sports evaluation identified constant alternation between a junctional and idioventricular rhythm in a 9-year-old child. During exercise testing, electrography demonstrated that the child was in junctional rhythm without any apparent P waves, and had a reduced increase in heart rate. Endocardial atrial pacing captured the atrium and demonstrated that atrioventricular conduction was normal, but the recovery time of the ectopic rhythm was very long. Three-dimensional electrophysiological mapping revealed 1:1 retrograde homogeneous conduction through the right atrium.
Investigations: Electrocardiography, Holter monitoring, echocardiography, exercise stress testing, atrial pacing, three-dimensional electroanatomical mapping of the right atrium and genetic testing.
Diagnosis: Sinus node dysfunction.
Management: Pacemaker implantation was postponed until a later stage in the patient's development.