| Objectives: Outflow tract ventricular arrhythmia(OTA) is common in clinical practice. OTA included ventricular tachycardia(VT) and premature ventricular contraction(PVC) which originated from left ventricular outflow tract(LVOT) or right ventricular outflow tract(RVOT). A distinguishing protocol based on surface electrocardiogram(ECG) characteristics to deduce the origin of ventricular outflow tract arrhythmia had been proposed according to our previous retrospective study. This studywas to investigate the value of the distinguishing prospectively.Methods: ECG characteristics were analyzed in 210 consecutive patients with OTA referred to General Hospital of Shenyang Military Command for electrophysiological examination and radiofrequency catheter ablation between June 2011 and August 2014. The origin of OTA was deduced according to the distinguishing protocol proposed by us in each patient before the ablation procedure.The distinguishing was as follows: the R/S transition zones(first precordial lead with R/S ratio ≥ 1) in the precordial leads was firstly observed.(1) if the R/S transition occurred in V1 or V2 lead, the OTA origin is judged from LVOT;(2) if the R/S transition occurred in V4 to V6 lead, the OTA origin is judged from RVOT;(3) If the R/S transition occurred in V3 lead, then the V2 transition ratio was calculated by computing the percentage R-wave during VT divided by the percentage R-wave in sinus rhythm( SR) to deduced the origin of OTA. The site where OTA was successfully ablated was considered as the origin of OTA. The indexes of sensitivity and specificity were evaluated step by step.Results: There were 210 patients(69 male and 141 female, mean age 48.0±13.6 years) with OTA included in this study, and none of them had organic heart disease. VT with or without the same morphologic PVC as main clinical manifestation was showed in 13 patients, and frequent PVC was present in the other 197 patients. The numbers of patients with OTA originating from LCC, RCC, NCC, LCC and RCC continuity, and belowaortic valve was 26, 9, 1, 3, and 11 respectively. The number of patients with OTA originating from the septum, the free wall, between septum and free wall of RVOT, and above the pulmonary valve were 120, 30, 1 and 9 respectively. There were 29 cases with OTA morphology of R/S transition in lead V1 or V2, and the OTA origin was deduced as LVOT. Actually, there were 28 patients successfully ablated in LVOT and one patient in RVOT. The criteria of R/S transition in lead V1 or V2 for judgment of OTA origin from LVOT was with the sensitivity of 56.0%, specificity of 99.4%, positive predictive value of 96.6%, and negative predictive value of 87.8%. There were 111 cases with OTA morphology of R/S transition in lead V4 to V6, and the OTA origin was deduced as RVOT. Finally, there were 108 patients successfully ablated in RVOT and 3 patient in LVOT. The criteria of R/S transition after lead V3 for prediction of OTA origin from RVOT was with the sensitivity of 67.5%, specificity of 94%, positive predictive value of 97.3%, and negative predictive value of 47.5%. There were 70 cases with OTA morphology of R/S transition in lead V3, V2 transition ratio of LVOT origin OTA was larger than that of RVOT origin(1.36±0.62 vs 0.57±0.28, P<0.05). In patients with OTA morphology of R/S transition in lead V3, there were 16 cases with V2 transition ratio greater than 1.0 and 14 cases were successfully ablated from LVOT. If the criteria of V2 transition ratio greater than 1.0 was used for the judgment of OTA origin from LVOT, this step of the distinguishing protocol with the sensitivity of 73.7%, specificityof 96.1%, positive predictive value of 87.5% and negative predictive value of 90.7%. However, there were 35 cases with V2 transition ratio greater than 1.0 and only 15 cases were successfully ablated from LVOT. this step of the distinguishing protocol with the sensitivity of 78.9%, specificity of 66.2%, positive predictive value of 42.9%, and negative predictive value of 88.6%.Conclusions: OTA has its own unique ECG characteristics. This prospective study suggested The criteria of deducing the origin of OTA from LVOT by R/S transition before lead V3 and the criteria of deducing the origin of OTA from RVOT by R/S transition after lead V3 had a high specificity. In patients with R/S wave transition in lead V3 during OTA, V2 transition ratio played an important role in deducing the origin of OTA. V2 transition ratio ≥1.0 as a criteria for predicting OTA origin from LVOT was more accuracy than V2 transition ratio ≥0.6 as a criteria. The protocol used in this study of distinguishing LVOT origin from RVOT origin had a great clinical utility and accuracy. |
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