Frequency of Fractionated Ventricular Activation and Atrial/Ventricular Electrogram Amplitude Ratio at Successful Ablation Target of Accessory Pathways in Patients with Ebstein's Anomaly

INTRODUCTION: Knowledge about local electrogram and atrial/ventricular electrogram amplitude ratio (A/V ratio) at the true atrioventricular ring for successful ablation of accessory pathways (APs) in patients with Ebstein's anomaly is limited. METHODS: Twenty-two adults with Ebstein's anomaly and APs were managed by 24 sessions of radiofrequency catheter ablation (RFCA). A right atrial/ventricular angiogram with or without 3-dimensional electroanatomic mapping was performed to delineate the true atrioventricular ring and atrialized right ventricle (ARV). Electrograms of successful targets were analyzed. For each right-sided AP target, 2 AP targets matched by location and conduction property from normal hearts were selected as controls, and their A/V ratios were compared. RESULTS: In 32 right-sided APs of all 22 patients, local ventricular activation at successful site presented as normal electrogram in 14, fractionated ventricular electrogram (FVE) in 16, and double ventricular potentials in 2. The bipolar voltage of ARV was markedly lower than in normal hearts. The A/V ratio at the successful target was significantly higher in APs with FVE than in control (1.64 ± 1.34 vs. 0.47 ± 0.19, P < 0.01), and was similar in APs with normal ventricular electrogram and in the control (0.38 ± 0.15 vs. 0.46 ± 0.15, P = 0.1726). The A/V ratio at the successful target with double ventricular potentials (after surgical correction) was 0.30 ± 0.20. All APs were successfully ablated without complications. CONCLUSIONS: In patients with Ebstein's anomaly, FVE was found in 50% of the successful targets of APs. High A/V ratio at successful sites with FVE and normal A/V ratio at targets with normal ventricular electrogram can facilitate target recognition and ablation.