A quantitative and qualitative analysis of the virtual unipolar electrograms from non-contact mapping of right or left-sided outflow tract premature ventricular contractions/ventricular tachycardia origins

This study was conducted to examine the virtual unipolar electrogram configuration of right/left outflow tract (OT) premature ventricular contraction (PVC)/ventricular tachycardia (VT) origins obtained from a non-contact mapping system (NCMS). The subjects consisted of 30 patients with OT-PVCs/VT who underwent NCMS-guided ablation. We evaluated the virtual unipolar electrograms of the origin on 3D right ventricular (RV)-OT isochronal maps. Successful ablation was achieved from the RV in 20 patients (RVOT group), and it failed in 10 (non-RVOT group: including left-sided/pulmonary artery/deep RVOT foci). On the virtual unipolar electrograms, the earliest activation (EA) preceded the QRS onset by 11.2 +/- 2.6 ms in the RVOT group and by 7.4 +/- 10.5 ms in the non-RVOT group (P = 0.138). The negative slope of the electrogram at the EA site (EA slope(5)), quantified by the virtual unipolar voltage amplitude 5 ms after the EA onset, was significantly steeper in the RVOT group than in the non-RVOT group (0.66 +/- 0.52 mV vs. 0.14 +/- 0.17 mV, P = 0.005). Cutoff values for the EA-to-QRS onset time and EA slope(5) of >= 8 ms and > 0.3 mV, respectively, completely differentiated the RVOT group from the non-RVOT group. A lesser EA slope(5) was associated with a greater radiofrequency energy delivery required to terminate RVOT-PVCs/VT. These demonstrate the importance of the virtual unipolar electrograms from OT-PVC/VT origins obtained with the NCMS. The virtual EA predicts both successful and potentially difficult ablation sites from the RV side.