Po-04-169 delayed effect of catheter ablation for intramural outflow tract ventricular arrhythmias

Despite sequentially bilateral outflow tract catheter ablation, intramural septal outflow tract ventricular arrhythmia (OT-VA) can be clinically challenging. The outcome of intramural septal OT-VA without complete elimination after sequentially bilateral ablation remains unknown. We aimed to investigate the outcome of intramural septal OT-VA without complete elimination after sequentially bilateral catheter ablation. During 2008 to 2020, patients with intramural OT-VA undergoing sequentially bilateral ablation were recruited. ECG and electrophysiological parameters were analyzed. The intramural OT-VA was defined by one of the following: 1. Difference of activation time between right and left ventricular outflow tract < 20 ms; 2. Pacemapping at the earliest activation site could not yield 12/12 matched morphology; 3. Catheter ablation at the earliest activation site could not completely eliminate the ventricular arrhythmia. Partial success was defined by a > 80% reduction in ventricular arrhythmia burden immediately after ablation. Delayed resolution was defined by a ventricular arrhythmia burden persistently < 2% of total daily beats during follow-up. In total, 124 patients (76 men, age: 53.5 ± 14) with intramural OT-VA undergoing sequentially bilateral ablation were studied. Acute success, partial success, and failure were found in 85 (68.5%), 26 (21.0%), and 13 (10.5%) patients respectively. For the patients with partial success, after a median follow-up period of 17.4 months (25%-75%, interquartile range: 2.8-53.2), recurrence and delayed resolution were observed in 21 and 5 (19.2 %) patients, respectively. The delayed effect was observed within 3.0 (25%-75%, interquartile range: 1.9-10.6) months after ablation (Figure). Of 5 patients with delayed resolution, the ventricular arrhythmias were characterized by left bundle branch block morphology and dominantly precordial R/S transition at V3, and the activation time of ventricular arrhythmias at right ventricular outflow tract was earlier than those at left ventricular outflow tract. Despite partial success could be achieved immediately after bilateral ablation of intramural OT-VA, the recurrence rate was still high. Delayed resolution of intramural OT-VA could only be observed in 19.2% of patients and the majority of ventricular arrhythmia resolution was observed within 3 months after catheter ablation.