Electrocardiographic Algorithms To Differentiate The Origin Of Outflow Ventricular Tachycardias

Part One:A simplified two-stepwise electrocardiographic algorithm to distinguish left from right ventricular outflow tract tachycardia originBackground:There are several electrocardiographic algorithms to predict the origin of idiopathic outflow tract ventricular arrhythmias(OT-VAs),but their usefulness and accuracy remain limited.This study was aimed to develop a more accurate and efficient stepwise electrocardiographic algorithm to discriminate left ventricular outflow tract(LVOT)from right ventricular outflow tract(RVOT)origin.Methods:We analyzed 12-lead electrocardiographic characteristics of 173 consecutive OT-VAs patients(RVOT,n=124;LVOT,n=49)underwent successful radiofrequency catheter ablation in Fuwai Hospital between January 2017 and December 2018,and developed an effective and accurate stepwise surface ECG algorithm,then validated it in a prospective cohort.Results:Based on the areas under the receiver operating characteristic curves,the combination of transitional zone(TZ)index<0 and V2S/V3R index≤1.5 exhibited 93.5%sensitivity,85.9%specificity,87.3%accuracy in the overall analysis of 173 OT-VAs.A further analysis was performed in the 71 OT-VAs with a V3-lead precordial transition,the sensitivity,specificity and accuracy of the integration of V2S/V3R index ≤ 1.5 and R-wave deflection interval in lead V3>80ms was 91.7%,83.1%and 85.9%.In the prospective evaluation,the combination of TZ index and V2S/V3R index could identify the correct origin sites with 91.2%accuracy in overall analysis,and the integration of V2S/V3R index≤1.5 and R-wave deflection interval in lead V3>80ms exhibited 94%accuracy in V3-lead precordial transition.Conclusion:The combination of TZ index<0 and V2S/V3R index ≤1.5 is a simple and efficient stepwise ECG algorithm for predicting LVOT origin.For the OT-VAs with a V3-lead precordial transition,the integration of V2S/V3R index ≤ 1.5 and R-wave deflection interval in lead V3>80ms will be a better choice.Part Two:Distinguishing Ventricular Arrhythmias Originating from the Posterior Right Ventricular Outflow Tract,or Near the Right Coronary Cusp or Near the His-bundleBackground:Differentiation of outflow tract ventricular arrhythmias(OT-VAs)which are originating from the posterior right ventricular outflow tract(RVOT),right coronary cusp(RCC)or near the His-bundle are still a challenge until now.This study was aimed to develop a stepwise electrocardiogram(ECG)algorithm to distinguish their locations.Methods:Seventy-five consecutive patients with ventricular arrhythmias successfully ablated from the posterior RVOT(n=57),near the His-bundle(n=5)or RCC(n=13)were enrolled in our study.Measurements with highest diagnostic performance were chosen to develop a diagnostic algorithm.Results:Of all these ECG measurements,the R-wave amplitude in lead I and V2S/V3R index showed the best diagnostic performance to discriminate these anatomical sites.The optimal ECG discriminators were different combination of lead I and V2S/V3R index as follows:the posterior RVOT,Lead I R-wave amplitude<0.65mV and V2S/V3R index>1.5(96.2%sensitivity,69.6%specificity);the near the His-bundle,lead I R-wave amplitude≥0.65mV and V2S/V3R index>1.5(100%sensitivity,70%specificity);RCC,lead I R-wave amplitude<0.65mV and V2S/V3R index≤1.5(52.9%sensitivity,93.1%specificity).Sequential algorithmic application of these criteria resulted in an overall accuracy of 83%in predicting site of OT-VA origin.Conclusion:A predominantly positive R-wave in lead I is seen in OT-VAs originated near the His-bundle.A stepwise ECG algorithm of combination with R-wave amplitude in lead I and V2S/V3R index could localize the origins of OT-VAs from the posterior RVOT,near the His-bundle and the RCC with a high accuracy.