A 23 year old female with manifest Wolff-Parkinson-White (WPW) syndrome presented for catheter ablation in April 2019. Twelve-lead EKG showed ventricular pre-excitation (Fig. 1A). Earlier electrophysiology study (EPS) with conventional mapping suggested two difficult located right-sided accessory pathways (AP). Since catheter ablation was not entirely successful, the patient was scheduled for ultra-high-density electroanatomical mapping (UHD-EAM) using a mini-basket catheter (IntellaMap Orion™) for electrogram acquision in combination with the automatic annotation procession software of the Rhythmia HDx™ system (all Boston Scientific) creating a detailed voltage and activation map of the atrium. The goal was to identify the location of the APs and to perform radiofrequency ablation based on UHD mapping information.

Diagnostic catheters were placed in the high right atrium, right ventricular apex, His bundle position, and coronary sinus. The Orion catheter was placed in the RA. An orthodromic WPW-tachycardia (CL 385ms) with rate-dependent RBBB morphology could be induced by premature ventricular stimulation (600/320/300ms) showing antegrade conduction via His and retrograde conduction via AP. An UHD-EAM was generated during tachycardia and confirmed a broad AP with the earliest atrial activation from lateral to superior at the tricuspid annulus in proximity to His (Fig. 2). The His bundle was mapped and highlighted. After successful RF ablation of the superior AP, surface EKG showed a different location of pre-excitation (Fig. 1B) and WPW-tachycardia was still inducible (CL 407ms). Another activation map revealed the remaining lateral AP (Fig. 2B). Because of catheter instability, a steerable sheath from femoral and a transjugular access for the ablation catheter (8mm Blazer II EPT, both Boston Scientific) were used to improve catheter positioning and energy application for successful ablation. For this reason and because of early conduction recovery of the lateral AP, a total of 52 RF applications (max. 80W, max. 80s, total 2375s) were finally necessary. At final EPS, no VA conduction was seen, nor was any tachycardia inducible by atrial and ventricular programmed stimulation. Normal His bundle conduction was confirmed. The delta wave disappeared on surface EKG (Fig. 1C). So far, the patient remained free from any symptoms of arrhythmia.

Our case showed that UHD-EAM can be useful to identify difficult locations of APs in WPW syndrome and successfully guide ablation therapy. This is particularly helpful when reduced catheter stability is expected, e.g. in right sided APs. Crucial structures of the conduction system that can be in close proximity to the ablation site can be highlighted using UHD-EAM and improve safety of the procedure.

Fig. 1   12-lead EKG

(A) Initial EKG shows short PQ interval, a broad QRS and positive delta waves in I, II, aVL, aVF, V1-6. (B) After ablation of the superior AP, delta waves were negative in II, III, aVF, V1-3, positive in I, aVL, and disappeared after ablation of both APs (C).

Fig. 2   Activation maps of the right atrium using UHD electroanatomical mapping

RFA ablation of the right superior accessory pathway (left; LAO view of the right atrium) and the right lateral accessory pathway (right; AP view). Silver tags: RF-ablation site. Yellow tags: His bundle.