RADIOFREQUENCY ABLATION OF THE SLOW PATHW AY IN RECIPROCATING NODAL RHYTHMS

Radiofrequency ablation is a therapeutic alternative to drug therapy i n recurrent reciprocating nodal rhythms. Selective ablation of the slo w pathway guided by endocavitary recordings has the advantage of being effective at the price of a very low incidence of atrioventricular bl ock. The authors report their experience with this technique. Fifty co nsecutive patients with recurrent attacks which were syncopal or uncon trolled by medical therapy, underwent selective ablation of the slow p athway, Firstly, they all underwent electrophysiological investigation to confirm the nodal origin of the reciprocating rhythm before procee ding to ablation itself, guided by the search for the slow pathway pot entials. After ablation, it was impossible to trigger reciprocating ta chycardia. Interruption of the anterograde slow pathway was achieved i n 24 patients and of the retrograde pathway in 1 patient; the other 25 patients went on having dual conduction but with a prolongation of th e effective refractory period of the slow pathway (268 +/- 46 ms vs 25 1 +/- 41 ms; p < 0.01). There were no cases of permanent complete atri oventricular block. interruption of the slow pathway was associated wi th 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 radiofreq uency ablation which was successful. The authors conclude that guided selective radiofrequency of the slow intranodal pathway is a remarkabl y effective and reliable method of treating poorly tolerated or resist ant reciprocating nodal tachycardias. Widening of the clinical indicat ions to patients not wishing to undergo long-term antiarrhythmic thera py now possible.