The present case report is of a 36-year-old man who had been symptomatic for frequent palpitations for 4 years after a prolonged febrile episode. The electrocardiogram on admission revealed an iterative supraventricular tachycardia at rate of 110 bpm, with ventriculoatrial interval of 180 ms and superior P-wave axis. Electroanatomic mapping showed substantially normal values in the right atrium other than an area along the posteroseptal region of the tricuspid annulus, with a low-voltage region that correlated with the area of earliest activation.