Late onset of accessory pathway conduction in a patient with complete AV block

This case report discusses a patient with complete AV block in early childh ood. The patient required a permanent pacemaker. At 6 years of age, intermi ttent preexcited beats were noted on telephonic transmissions. At 7 years o f age, 1:1 preexcitation was noted in sinus rhythm. Therefore, late onset o f antegrade accessory pathway function is demonstrated. This case provides evidence of developmental changes in accessory; pathways. This may explain age related differences in the onset of narrow complex tachycardia in the s chool age pears.