0164: Evolution of preexcitation syndrome in children

Previous studies reported a spontaneous disappearance of preexcitation syndrome (PS) in patients with a long accessory pathway (AP) effective refractory period (ERP) and in children <12 years (y), but stability in children >12 y with inducible SVT and short AP-ERP. The purpose of the study was to collect the data of untreated children with a PS, studied 2 times at least one year of interval.Methods2 baseline electrophysiological studies (EPS) were performed within 1 to 25 years of one another (mean 6±years) in 39 children and teenagers, 17 boys, 22 girls, aged initially from 1 to 19 years (12.5±4), with overt PS. First EPS (EPS1) was indicated for syncope (n=4), atrioventricular reentrant tachycardias (AVRT)(n=17) or for asymptomatic PS (n=18). The protocol was similar, performed in control state (CS) and after isoproterenol.ResultsAt EPS2, among patients studied for syncope at EPS1, 1 has still syncope, 2 have AVRT, 1 is asymptomatic. Among patients with AVRT at EPS1, 14 (82%) have still AVRT, 3 are asymptomatic. Among asymptomatic patients, 13 (72%) remain asymptomatic, 2 have AVRT, 3 have syncope. AVRT in children presenting initially with syncope or initially asymptomatic children occurred in 2/4 with inducible AVRT at EPS1. The higher rate conducted by AP was similar in CS and after isoproterenol at EPS2 (178±72bpm, 203±81) and at EPS1 (188±62, 237±83)(p<0.01). AP-ERP’s were similar in CS at EPS2 (283±68ms) and 1 (281±91.5) and tended to increase from 211±72 at ESP1 to 234±58ms at EPS2 (p