Baseline characteristics
In this study, 100 patients (48 men, mean age 62.77 ±14.10 years, and 52 women, mean age 60.00 ±13.15 years) who underwent successful ablation in either the RVOT or the LVOT were enrolled. All these patients had taken at least one antiarrhythmic drug, including metoprolol, propafenone, or amiodarone. According to the successful ablation site, in 63 (63.00%) patients, the VA had originated in the RVOT, and in 37 (37.00%) patients, it had originated in the LVOT. The LVOT group comprised 14 (37.84%) patients with left coronary cusp (LCC), 9 (24.32%) patients with right coronary cusp (RCC), 10 (27.03%) patients with left ventricular endocardium below the aortic sinus cusp (ASC), and 4 (10.81%) patients with GCV-AIV.
Comparison of the previous ECG parameterswithout restrictions in thetransition lead
In the previous ECG parameters, the V2 transition ratio, V3 R-wave deflection interval, and V1–V3 transition index were used in the OTVAs, with the transition lead in V3. The other seven parameters could be used in the OTVAs without restrictions in the transition lead. Therefore, the 100 patients with OTVAs were analyzed with the other seven parameters using ROC curve analysis (Figure 1A). The V2S/V3R index (AUC = 0.89, p = 0.00) was superior to S-R difference in leads V1 and V2 (AUC = 0.87, p = 0.00) and the TZ index (AUC = 0.75, p = 0.00) in predicting the origin of the RVOT. Further, the larger ISA in leads V1 and V2 (AUC = 0.90, p = 0.00) was superior to the larger R/S-wave amplitude index in leads V1 and V2 (AUC = 0.87, p = 0.00), the larger R-wave duration index in leads V1 and V2 (AUC = 0.84, p = 0.00), and the amplitude of the QRS complex in the initial 40 ms in V2 (AUC = 0.65, p = 0.04) in predicting the origin of the LVOT. Table 2 compares the accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the ECG parameters for predicting the origin of the LVOT.
Among the parameters, the V2S/V3R index was significantly greater for VAs originating from the RVOT. The Youden index was 0.65, and the optimal cutoff value was 1.5 (Figure 1B). Further, the accuracy was 81.00%, sensitivity was 79.37%, specificity was 83.78%, PPV was 89.29%, and NPV was 70.45%.
The larger ISA in leads V1 and V2 was significantly greater for VAs originating from the LVOT. The Youden index was 0.62, and the optimal cutoff value was 57 ms × mv (Figure 1C). The accuracy was 82.00%, sensitivity was 81.08%, specificity was 82.54%, PPV was 73.17%, and NPV was 88.14%.
Comparison of the previous ECG parameterswith the transition lead in V3
An additional ROC analysis (Figure 2A) for the previous 10 parameters was performed among 37 (37.00%) patients with the transition lead in V3. The V2S/V3R index (AUC = 0.82, p = 0.01) was better than the S-R difference in leads V1 and V2 (AUC = 0.78, p = 0.02) in predicting the origin of the RVOT. Further, the V3 R-wave deflection interval (AUC = 0.81, p = 0.01) was better than the larger ISA in leads V1 and V2 (AUC = 0.77, p = 0.02) and larger R/S-wave amplitude index in leads V1 and V2 (AUC = 0.77, p = 0.02) in predicting the origin of the LVOT. The other parameters in predicting the origin of VAs with the transition lead in V3 were not statistically significant (Table 3).
Among the parameters, the V2S/V3R index was significantly greater for VAs originating from the RVOT. The Youden index was 0.59, and the optimal cutoff value was 1.5. The accuracy was 72.97%, sensitivity was 75.00%, specificity was 72.00%, PPV was 56.25%, and NPV was 85.71%. On the other hand, the V3 R-wave deflection interval was significantly greater for VAs originating from the LVOT. The Youden index was 0.73, and the optimal cutoff value was 80 ms (Figure 2B–2D). The accuracy was 86.49%, sensitivity was 75.00%, specificity was 92.00%, PPV was 81.82%, and NPV was 88.46%.
Appropriate ECGalgorithm for reliably predicting VA origin
For VAs without restrictions in the transition lead, the algorithm (Figure 3) combining the V2S/V3R index and larger ISA index could predict VA origin with an accuracy of 85.00%, a sensitivity of 75.68%, a specificity of 90.48%, a PPV of 82.35%, and an NPV of 86.36%. For VAs with the transition lead in V3, no statistical significance was observed in the accuracy of predicting VA origin between the V3 R-wave deflection interval and the algorithm (86.49% vs. 85.00%, p = 0.528). Therefore, the algorithm can reliably determine OTVA origin without restrictions in the transition lead.