Mapping and RFCA
Bipolar and unipolar intracardiac electrograms were filtered at 30–400 and 0.05–400 Hz, respectively, and the surface ECG was filtered at 0.05–30 Hz. If patients had sufficient VA with or without isoproterenol (2–4 µg/min), local activation time mapping was performed to identify the earliest bipolar ventricular electrograms, accompanied by a unipolar QS pattern wave. On the other hand, if patients had an insufficient VA, pace mapping was performed at a pacing cycle length of 500 ms. Then, the paced and the spontaneous VAs were closely compared to determine the target for RFCA. The site of VA origin was determined using the electroanatomic maps from the RAO and LAO views.
Radiofrequency energy was delivered to the distal electrode of the irrigated 3.5-mm tip catheter at a temperature limit of 55°C and power setting of 30 W. In cases where the target was within the great cardiac vein near the anterior interventricular vein (GCV-AIV), the power was started from 15 W and increased up to 30 W. In other cases where the target was adjacent to the intense fibrous structures or there was suppression and recurrence of VA, a power of up to 40 W was used. The ablation duration of each site was approximately 60 s, with a maximum duration of 120 s.
Successful ablation success was achieved when (1) clinical VA was eliminated at the end of the procedure; (2) clinical VA was absent after 24 h of continuous ECG monitoring without antiarrhythmic drugs; and (3) there was no recurrence of clinical VA during >3 months of follow-up. All of these predescribed criteria should be satisfied to achieve successful ablation.
Validation study
After developing the algorithm for predicting OTVA origin, we validated it by including another 100 patients from two different hospitals between June 2020 and October 2022.