A longitudinal study on electrophysiological properties of atrioventricular accessory pathways in infants and children.

In this study the electrophysiological developmental changes of accessory pathway (AP) properties in infants and children are examined. Intracardiac and/or transesophageal electrophysiological studies were performed on seven infants (group 1, mean age 2 months) and four children (group 2, mean age 9 y; study 1), and documented orthodromic atrioventricular tachycardia in all cases. At follow-up study (study 2), supraventricular tachycardia was induced in three of seven (43%) cases in group 1 and in all four cases in group 2. Changes in antegrade conduction properties of AP were documented by loss of pre-excitation (two of four cases in group 1) or change to intermittent pre-excitation (one of two cases in group 2).