The mechanisms of supraventricular tachycardia in children.

The mechanisms of supraventricular tachycardia were investigated in 35 children. Intracardiac electrograms including His bundle potentials were recorded. Atrial pacing and single premature atrial stimuli were performed in the right atrium. Tachycardia was observed and the mechanism elucidated in 33 patients. The atrial activation sequence during tachycardia, including high right atrium, low lateral right atrium, low septal right atrium, and left atrium, together with the ability to initiate or terminate the tachycardia with premature stimuli, were keys to defining the mechanisms. The observed mechanisms included atrioventricular (A-V) node reentry (8), sino atrial node re-entry (5), re-entry through manifest or concealed lateral anomalous pathway (8), re-entry through A-V node bypasses (3), and atrial (7) and junctional (2) ectopic focuses. The frequency of the various mechanisms of SVT is more varied in children than adults, with ectopic mechanisms being more common in children.