EGM characteristics of intramural outflow tract ventricular arrhythmias

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Successful ablation of outflow ventricular premature contractions (VPC) depends on the identification of earliest activation. Annotation of bipolar (bi) EGMs can be challenging for especially multicomponent EGMs. Universally, annotation of earliest depolarization which depends on maximum dV/dt of unipolar (uni) EGMs and uni-QS morphology identify site of origin for VPC. However, identification of uni-QS morphology has limitations due to low spatial resolution. Additionally, time difference between bi- and uni-EGM can be observed and may be associated with deeper origin. Aim of this study is to compare EGM characteristics at successful ablation site in RVOT and RVOT+LVOT VPC ablation cases. Methods In this retrospective study, 40 patients who underwent successful RFA for RVOT and RVOT+LVOT VPCs were included. Local activation time (LAT), duration and voltage data of each bi- and uni-EGM at the successful ablation sites from RVOT and RVOT+LVOT cases were analyzed. Results 28/40 (70%) of patients were ablated from RVOT and in 12/40 (30%) required both side ablation. All patients had acute PVC suppression. Bi-EGM-QRS onset was earlier (36.2±13.8 ms vs 28.8±7.3 ms, p=0.03), duration of bi-EGM was shorter (58.2±19.6 ms vs 83.8±22.3 ms, p=0.003) and Bi-voltage amplitude was higher (3.1±2.4 mV vs 1.2 ±0.9 mV, p=0.01) for patients with RVOT only ablation. Mean Bi-Uni EGM difference was 5.6±5.1ms in the RVOT group vs 13.5±5.4 ms in RVOT+LVOT group (p<0.001). Uni-QS morphology was recorded in 3.6±4.5 vs 3.3±1.9 cm2 in RVOT and RVOT+LVOT group respectively (P=0.80). In 11/40 (28%) of patients uni-QS was not identified at successful ablation site. Conclusion QS in uni-EGM was not a perfect predictor for successful ablation sites. Analysis of bipolar voltage amplitude and duration with Bi-uni EGM time difference may identify deeper source.