A 10-year-old boy with polyvalvular dysplasia and severe involvement of both atrioventricular valves presented with palpitations. Concern was raised for atrial tachyarrhythmia due to biatrial enlargement; however, ambulatory monitoring discovered a reentrant mechanism. Electrophysiology study revealed atypical atrioventricular nodal reentrant tachycardia involving two components of the slow pathway, with inputs in the posterior septum around his dysplastic tricuspid valve. He underwent successful modification of the slow pathway using cryoablation.
