[Atrioventricular nodal tachycardia with left-sided slow pathway treated with RF ablation].

We present a case of 10-year-old boy with AVNRT. The tachycardia had prolonged RP interval (160 ms) and HA time (135 ms). The application at the rim of the coronary sinus resulted in accelerated junctional rhythm and retrograde block followed by transiently prolonged atrioventricular conduction. The mapping of the mitral annulus transeptally presented no 'slow potentials'. The electrode was then inserted retrogradely through the aorta and slow potentials were recorded on the septal aspect of the left atrium. Two RF applications at this site were successful. The patient was followed for three years without recurrence of arrhythmia.