[Ablation of the slow pathway in reciprocating nodal rhythms by radiofrequency]

Radiofrequency ablation is a therapeutic alternative to drug therapy in recurrent reciprocating nodal rhythms. Selective ablation of the slow pathway guided by endocavitary recordings has the advantage of being effective at the price of a very low incidence of atrioventricular block. The authors report their experience with this technique. Fifty consecutive patients with recurrent attacks which were syncopal or uncontrolled by medical therapy, underwent selective ablation of the slow pathway. Firstly, they all underwent electrophysiological investigation to confirm the nodal origin of the reciprocating rhythm before proceeding to ablation itself, guided by the search for the slow pathway potentials. After ablation, it was impossible to trigger reciprocating tachycardia. Interruption of the anterograde slow pathway was achieved in 24 patients and of the retrograde pathway in 1 patient : the other 25 patients went on having dual conduction but with a prolongation of the effective refractory period of the slow pathway (268 +/- 46 ms vs 251 +/- 41 ms : p < 0.01). There were no cases of permanent complete atrioventricular block. Interruption of the slow pathway was associated with shortening of the effective refractory period of the rapid pathway (323 +/- 71 ms vs 348 +/- 80 ms : p < 0.01), which was not observed in cases of persistent dual conduction. No recurrence of tachycardia was observed during follow-up (mean period = 19.2 months) : however, control endocavitary studies in 25 asymptomatic patients after 1 to 3 months showed recurrence in 4 cases, which led to immediate further radiofrequency ablation which was successful. The authors conclude that guided selective radiofrequency of the slow intranodal pathway is a remarkably effective and reliable method of treating poorly tolerated or resistant reciprocating nodal tachycardias. Widening of the clinical indications to patients not wishing to undergo long-term antiarrhythmic therapy is now possible.