216-33: High resolution mapping and ablation of a recurrent left lateral accessory pathway conduction

Purpose of the study: The proper localization of an oblique orientated accessory pathways (AP) and the ability to detect clear AP potentials on ablation catheter are crucial for successful AP ablation. We report a case of recurring AP conduction that was finally eliminated using a novel ablation catheter equipped with high-resolution mini-electrodes.

Method used: A 35-year-old male patient presented for RF ablation of Wolff–Parkinson–White syndrome. A manifest left lateral AP was suspected based on delta wave polarity on ECG. Electrophysiological study (EPS) showed the earliest ventricular activation (EVA) at dipole CS 1–2 in sinus rhythm. Programmed incremental right ventricular apex pacing revealed eccentric retrograde atrial activation, with the earliest atrial activation between CS 5–6 and CS 3–4. Based on these findings, an oblique AP was diagnosed. The ablation target was the site of EVA with absence of AP potential and fusion of atrial (A) and ventricular (V) EGM.

Summary of results: The ablation was firstly attempted with a 4 mm tip temperature-controlled ablation catheter. Despite intra-procedural success, on the first day evidence of delta wave recurrence was detected on ECG and the same AP pattern was confirmed at EPS. A second ablation attempt was performed using a 3.5 mm tip open irrigated ablation catheter over a broader area around the target spot. Adenosine was infused to confirm absence of pre-excited beats after ablation, however after 1 month the ECG revealed recurrence of pre-excitation. A third ablation was attempted using a 8 mm tip ablation catheter (Intella Tip MiFi XP, Boston Scientific) equipped with 3 mini-electrodes (MEs) at the distal tip. Although the conventional ablation dipole did not allow to detect signals between A- and V-EGMs (isoelectric line), fractionated atrial signals fused with a V-EGM were revealed on MEs at the target position and RF energy was delivered. Remapping the ablation area, we identified on MEs only, a discrete, high frequency narrow spike between A- and V-EGMs in absence of ventricular pre-excitation, indicating a preserved AP conduction. Additional RF energy was delivered until complete disappearance of AP potential on MEs. During 3 months follow up the patient remained free from any sign of pre-excitation and symptoms.

Conclusion: Smaller and closer electrodes result in high mapping resolution with less signal averaging and cancellation effects. Due to the improved sensitivity, the Intella Tip MiFi catheter seems effective in detecting fragmented and high frequency signals like AP potentials, thus improving ablation success.