Preexcitation unmasked after successful accessory atrioventricular connection ablation: what is the mechanism?

摘要

A 19-year-old man with a history of palpitations and no underlying structural heart disease underwent electrophysi-ologic diagnostic evaluation for possible catheter ablation of the arrhythmogenic substrate responsible for the palpitations. Twelve-lead ECG showed ventricular preexcitation consistent with a left free-wall accessory atrioventricular (AV) connection (Figure 1A).Electrophysiologic study was performed using standard methodology with catheters in the right ventricular apex (RVA), high right atrium (HRA), His bundle, and coronary sinus. Basic intervals during sinus rhythm were as follows: PR interval 110 ms, AH interval 40 ms, HV interval 0 ms, and QRS duration 110 ms. Ventricular preexcitation was maximal during incremental atrial pacing (Figure IB). Ventricular pacing showed nondecremental and eccentric retrograde ventriculoatrial (VA) conduction. HRA programmed stimulation induced a minimally preexcited AV reciprocating tachycardia with eccentric VA conduction (Figures IB and 2A). Measurements of the tachycardia were as follows: AH interval 238 ms, HV interval 16 ms, and VA interval 151 ms. Retrograde conduction was due to a left free-wall accessory AV connection. However, during tachycardia, the HV interval was shorter than expected (Figure 2A). We performed radiofrequency catheter ablation of the left free-wall accessory AV connection with subsequent VA dissociation during RVA pacing.