Supplementary Material for: Differentiating origins of outflow tract ventricular arrhythmias: the correction of transitional zone index is not superior to the original one

Background: Our team once proposed a correction of transitional zone index (CTZI) based on the transitional zone index (TZI) in view of achieving a more precise prediction of outflow tract ventricular arrhythmias (OTVAs). The predictive accuracy of these two electrocardiogram (ECG) algorithms has not been validated and compared. The purpose of this study was to compare the predictive accuracy of TZI and CTZI in a much larger population with idiopathic OTVAs.
Methods: The predictive accuracy of TZI and CTZI were compared in 695 individuals with idiopathic premature ventricular complexes or ventricular tachycardia which exhibited a left bundle branch block pattern and inferior axis QRS morphology. Receiver operating characteristic curve analysis, decision curve analysis and calibration curve were used to compare the predictive accuracy of TZI and CTZI.
Results: TZI and CTZI manifested the similar area under the curve. While a TZI of <0 predicted a left ventricular outflow tract (LVOT) origin with a high specificity of 88.2% but a low sensitivity of 67.1%, a CTZI of <0 yielded a high sensitivity of 84.3% but a low specificity of 59.5% in the overall analysis. Similar results were yielded in the sub-analysis of participants with a precordial transition occurred at lead V3. In the sub-analysis of participants with a TZI =0, CTZI demonstrated a bit higher but not satisfactory predictive accuracy than TZI.
Conclusion: Based on the scientific spirit of self-criticism and seeking truth from facts, our team disproves the correction of TZI proposed previously.