Sick sinus syndrome is uncommon in children, and syndromic forms are rare. Some forms of sick sinus syndrome like the bradycardia-tachycardia type could be managed by a radiofrequency ablation, even in young children, and could be helpful to delay the implantation of a pacemaker.
van der Haert, L., & Blommaert, D. (2018). Pulmonary veins isolation to retard pacemaker implantation. Clinical Case Reports, 6(12), 2445-2450. https://doi.org/10.1002/ccr3.1865 (Original work published 2018)