Unipolar and bipolar electrogram characteristics of recurrent cases of idiopathic ventricular arrhythmias undergoing repeat catheter ablation

Limitations of Unipolar Signals in Guiding Successful Outflow Tract Premature Ventricular Contraction Ablation

OBJECTIVES

The authors sought to compare bipolar electrograms (BiEGMs) vs unipolar electrograms (UniEGMs) in guiding successful ablation of right ventricular outflow tract (RVOT) vs intramural outflow tract (OT) premature ventricular contractions (PVCs). The authors hypothesized that: 1) earliest bipolar local activation time (LAT_Bi) would better guide mapping and ablation, vs UniEGM dV/dt (LAT_Uni) or QS morphology; and 2) LAT differences using bipolar vs unipolar EGMs (ΔLAT_Bi-Uni) would be greater for intramural OT than RVOT PVCs.

BACKGROUND

UniEGMs are commonly used to annotate earliest local activation of focal arrhythmias. However, their utility in guiding PVC ablation may be limited when the PVC source is less superficial.

METHODS

Consecutive patients undergoing successful PVC ablation 2017 to2020 requiring only RVOT or RVOT+left ventricular OT (RVOT+LVOT) ablation were retrospectively analyzed. BiEGMs and UniEGMs at successful ablation sites were compared.

RESULTS

Of 70 patients, 50 required RVOT-only, and 20 required RVOT+LVOT ablation for acute and long-term PVC suppression. Mean ΔLAT_Bi-Uni was lower for RVOT vs RVOT+LVOT groups (9.3 ± 6.4 ms vs 17.4 ± 9.9 ms; P < 0.01). QS UniEGM was seen in 78% of RVOT, compared with 53% of RVOT+LVOT patients (P < 0.016). RVOT+LVOT sites most frequently included the posteroseptal RVOT and adjacent LVOT (73%), and 43% lacked a QS unipolar EGM. ΔLAT_Bi-Uni ≥15 ms best distinguished sites in which RVOT-only vs RVOT+LVOT ablation achieved acute PVC suppression (area under the curve: 0.77).

CONCLUSIONS

Earliest BiEGM activation guides successful ablation of OT PVCs better than UniEGM-guided analysis, especially when an intramural PVC source is present.