[Radiofrequency ablation of permanent supraventricular tachycardia through an accessory pathway with slow retrograde conduction].

We present the case of a 6 year old boy with permanent junctional reciprocating tachycardia. The tachycardia had been present since 3 years before ablation and was treated with two drugs without good control. He began to complain of palpitations and shortness of breath on exertion and the left ventricle ejection fraction was 55% by echocardiography. We performed an electrophysiologic study which showed the most early atrial activation at the coronary sinus with a long V-A interval. Orthodromic AV reciprocating tachycardia was confirmed as the mechanism of tachycardia by demonstrating atrial pre-excitation when a premature ventricular stimulus was delivered at the time the His bundle was refractory. With the ablation catheter, the accessory pathway potential was recorded at the coronary sinus near the os. Radiofrequency current was applied with temperature control at 60 degrees C for one minute at this site with success. While on sinus rythm we performed programmed atrial and ventricular stimulation with isoproterenol infusion and there was no evidence of accessory pathway function. This patient is asymptomatic and on sinus rythm 6 months later.