Amplitude of QRS complex within initial 40 ms in V₂ (V₂QRS_i40): Novel electrocardiographic criterion for predicting accurate localization of outflow tract ventricular arrhythmia origin

Background: The initial depolarization vector of outflow tract (OT) ventricular arrhythmia (VA) varies in different origins, which may help to predict OT-VA origin more accurately.

Objective: The purpose of this study was to develop a more accurate electrocardiographic (ECG) criterion for differentiating between left and right OT-VA origins.

Methods: We studied 275 patients with successful ablation in the right ventricular outflow tract (RVOT) (n = 207) or left ventricular outflow tract (LVOT) (n = 68) in the development cohort. Amplitude of the QRS complex within initial 40 ms (QRS_i40) in precordial leads was measured. A novel criterion for identifying OT-VA origin was developed based on the development cohort. Predictive performance of novel criterion was further validated by comparing with previous ECG criteria (V₂S/V₃R index, V₂ transition ratio, and transition zone index) in the validation cohort with 107 patients (RVOT 75; LVOT 32).

Results: QRS_i40 of identical precordial leads were significantly greater in the LVOT group than the RVOT group (P <.05). In the development cohort, QRS_i40 of V₂ (V₂QRS_i40) exhibited the greatest area under the curve of 0.950, with cutoff ≥0.52 mV predicting LVOT origin (sensitivity 86.0%; specificity 94.6%). In the validation cohort, V₂QRS_i40 ≥0.52 mV outperformed previous criteria in predictive performance (accuracy 90.7%; sensitivity 84.4%; specificity 93.3%). This advantage of V₂QRS_i40 over previous criteria also held true for subgroups of transition zone index = 0 and V₃ R/S transition.

Conclusion: V₂QRS_i40 is a novel and accurate ECG criterion to predict OT-VA origin that outperforms previous criteria.