Characteristics of Bipolar and Unipolar Electrograms at Optimal Ablation Sites for Ventricular Arrhythmias Originating Near the Left Ventricular Summit

Background Ventricular arrhythmias (VAs) arising near the left ventricular (LV) summit are often successfully ablated from adjacent anatomic sites. However, the role of bipolar and unipolar electrograms in guiding optimal ablation remains unclear. This study aimed to investigate whether bipolar and unipolar electrogram characteristics can help identify the most effective ablation sites for VAs near the LV summit. Methods We retrospectively analyzed patients with idiopathic VAs originating from the LV summit, excluding those with structural heart disease or reentrant mechanisms. Electrograms were evaluated at the earliest activation sites within the great cardiac vein/anterior interventricular vein, aortic sinus of Valsalva, subvalvular LV regions, and the right ventricular outflow tract. Bipolar local activation time (LAT Bi ) and unipolar local activation time were assessed. Results A total of 78 patients (mean age, 53.9±16.6 years; 59 men) with 80 VAs and 229 mapping points (60 in the great cardiac vein/anterior interventricular vein, 62 in the aortic sinus of Valsalva, 65 in subvalvular LV regions, and 42 in the right ventricular outflow tract) were analyzed. Ablation was successful at 65 sites. The mean LAT Bi at successful sites was 28.1±21.8 ms. Longer LAT Bi significantly predicted successful ablation (odds ratio, 1.07 [95% CI, 1.02–1.12]; P =0.004). The optimal LAT Bi threshold was 14 ms (sensitivity, 85%; specificity, 44%; area under the curve, 0.67). Unipolar local activation time, LAT Bi −unipolar local activation time differences, unipolar QS morphology, and unipolar waveform characteristics did not predict success. Conclusions Early LAT Bi was associated with successful ablation of LV summit VAs, whereas unipolar electrogram features were not independently predictive.