Patient presentation: A 28-year-old woman with a long-standing history of palpitations presented to the emergency department for syncope. Three years before, she had unsuccessful radiofrequency ablation for Wolf-Parkinson- White syndrome complicated by complete heart block necessitating dual-chamber pacemaker implantation. Following pacemaker implantation, she had partial recovery of atrioventricular conduction. A treadmill stress ECG after pacemaker implant revealed sinus rhythm at baseline with preexcitation in a pattern of a midseptal accessory pathway (AP). Her rhythm during recovery after stress was from the sinus node at 114 bpm with a prolonged PR interval (length) and a right bundle-branch block morphology without preexcitation. A repeat electrophysiology procedure shortly thereafter revealed ventricular preexcitation at baseline with no inducible arrhythmias with aggressive pacing maneuvers and isoproterenol infusion. There was no change in the degree of preexcitation despite decremental atrioventricular (AV) node conduction, and there was a preserved HV (His-ventricular) interval during incremental right atrial pacing and preserved ventricular preexcitation during junctional rhythm. These observations suggested a fasiculoventricular AP, but a standard AV AP that had been partially ablated during her previous procedure could not be excluded. The His-Purkinje conduction was abnormal with a prolonged HV interval, right bundle-branch block, and left anterior fascicular block. The AP mapped to a relatively wide area of the upper-mid right atrial septum and ablation was unsuccessful, despite extensive radiofrequency delivery to the right atrium septum. At that time, it was felt that the AP was most likely a fasiculoventricular pathway and did not participate in tachycardia. Her pacemaker was reprogrammed to VDD with long AV delay to minimize pacing. For the next 3 years, she remained asymptomatic until her episode of syncope.
- Accessory atrioventricular bundle
- Heart block
- Muscular diseases
- Muscular dystrophies, limbgirdle
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)