Cutoff values of the parameters
In our retrospective study, the cutoff values of V2S/V3R and the V3 R-wave deflection were the same as those in previous studies. However, compared with Nikoo et al.[10], the larger ISA in V1 and V2 (66.53 ±59.73 vs. 29.48 ±55.57) and the cutoff value of ISA (57 vs.15, P = 0.00) in our study were larger. After reviewing the data obtained from the previous study, we found that the duration of the R-wave in V1 (67.34 ±35.38 vs. 49.75 ±31.02) and V2 (71.09 ±25.26 vs. 53.08 ±27.72) and the amplitude of R-wave in V1 (0.38 ±0.31 vs. 0.20 ±0.26) and V2 (0.79 ±0.51 vs. 0.35 ±0.47) in our study were larger. This may be related to the inclusion of more patients with a transition lead in V1 (21.00% vs.10.00%) in our study. However, after excluding 21 patients with a transition lead in V1, the ISA (42.50 ±31.56 vs. 29.48 ±55.57) in our study was still larger than that in the previous study; the cutoff value remained unchanged (cutoff value = 57 and Youden index = 0.49). In addition, with a cutoff value of 57 in our validation study, we achieved satisfactory diagnostic accuracy (94.00%) and AUC (0.95), with a sensitivity of 97.06%, a specificity of 92.42%, a PPV of 86.84%, and an NPV of 98.39% (Table 4). Therefore, we believe that a cutoff value of 57 is more appropriate.