NONREENTRANT SUPRAVENTRICULAR TACHYCARDIA DUE TO SIMULTANEOUS CONDUCTION OVER FAST AND SLOW AV NODE PATHWAYS - SUCCESSFUL TREATMENT WITH RADIOFREQUENCY ABLATION

A 55-year-old woman with frequent problematic supraventricular tachyca rdia is presented. The tachycardia was irregular with predominately no rmal QRS morphology and was refractory to multiple antiarrhythmic drug s. At electrophysiology study, the tachycardia was inducible with atri al or ventricular extrastimuli and dual pathways were observed. In con trast to the situation usually seen with dual atrioventricular node ph ysiology, the slow pathway had a longer effective refractory period th an the fast pathway and reentrant tachycardia was not induced. Simulta neous conduction over the fast and slow pathways during sinus rhythm w as shown to be the mechanism for clinical tachycardia. The tachycardia was successfully treated using radiofrequency ablation of the slow pa thway.