Amplitude of QRS complex within initial 40 ms in V 2 (V 2 QRS i40): Novel electrocardiographic criterion for predicting accurate localization of outflow tract ventricular arrhythmia origin

Heart Rhythm. 2020 Jul 10;S1547-5271(20)30641-X. doi: 10.1016/j.hrthm.2020.07.006. Online ahead of print.


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 (QRSi40) 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: QRSi40 of identical precordial leads were significantly greater in the LVOT group than the RVOT group (P <.05). In the development cohort, QRSi40 of V2 (V2QRSi40) 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, V2QRSi40 ≥0.52 mV outperformed previous criteria in predictive performance (accuracy 90.7%; sensitivity 84.4%; specificity 93.3%). This advantage of V2QRSi40 over previous criteria also held true for subgroups of transition zone index = 0 and V3 R/S transition.

Conclusion: V2QRSi40 is a novel and accurate ECG criterion to predict OT-VA origin that outperforms previous criteria.

Keywords: Electrocardiogram; Novel criterion; Outflow tract; Radiofrequency catheter ablation; Ventricular arrhythmia.