Case Report: Ventricular Preexcitation Masking Complete Atrioventricular Conduction Block

Objectives: A 17-year-old young woman was admitted to our department for catheter ablation of a ventricular preexcitation pattern without clinical symptoms (“asymptomatic WPW”). Her history was remarkable for a previous failed radiofrequency (RF) ablation of a posteroseptal accessory pathway (AP) at a referring hospital. Otherwise, she had no other heart-related condition and was on no medication. A 12-lead ECG showed a ventricular preexcitation pattern associated with a posteroseptal location of accessory pathway.

Methods: After right femoral vein puncture, a 10-polar diagnostic catheter was inserted into the coronary sinus and a four-polar diagnostic catheter was inserted into the right ventricle. During atrial stimulation, a 1:1 AV-conduction over the AP was observed at a pacing interval of up to 300 ms. Retrograde conduction over the AP was observed up to 340 ms. Mapping of earliest ventricular activation was performed during sinus rhythm using a 4-mm irrigated tip ablation catheter. The earliest point of ventricular activation was in posteroseptal region inside the middle cardiac vein. Application of RF energy (30 W) resulted in termination of conduction over the AP and revealed complete AV block with no ventricular escape rhythm. RF ablation was stopped immediately and conduction over AP returned after a few seconds. No temporary pacing was required. As conduction over AP persisted for over 30 minutes in the electrophysiology laboratory, the procedure was discontinued. All catheters were removed. The patient was observed in the intensive care unit for 24 hours. On continuous 12-lead ECG monitoring, constant conduction over AP was observed.

Result: The exact cause of the underlying AV block is unknown, although we presume it to be congenital. It was decided to currently not implant a pacemaker due to lack of symptoms and age. She is scheduled for short-term follow-up.

Conclusion: Coexistence of complete AV block and ventricular preexcitation is very uncommon. Currently there are no accepted guidelines for the management of these patients. The decision to implant a pacemaker and to ablate the accessory pathway should be based on an individual basis.