Narrow complex tachycardia after slow pathway ablation: continue ablating?

摘要

A 37-year-old woman was referred for electrophysiologic study for paroxysmal supraventricular tachycardia. Resting 12-lead surface ECG revealed normal sinus rhythm without preexcitation. An electrophysiologic study was performed in the absence of medications. At baseline, the A-H interval was 58 ms and the H-V interval was 50 ms at 55 bpm. Typical slow-fast AV nodal reentrant tachycardia (AVNRT) with a cycle length (CL) of 360 ms was easily induced by ventricular and atrial pacing.Ablation lesions were placed in the presumptive slow pathway region between the tricuspid valve annulus and coronary sinus ostium, inducing slow junctional beats. Following ab-lation, atrial and ventricular pacing were repeated with occasional AV nodal echo beats but no inducible tachycardia. During isoproterenol infusion of 2 mcg/min narrow complex tachycardia occurred (Fig. 1). What is the mechanism of the tachycardia?