PCA, PLS-DA and VIP score of ECG and HRV. (A–B) represents the PCA and PLS-DA plot of ECG parameters involving all groups, respectively, with statistical values in the form of regression (R2 0.85). (D–E) represents the PCA and PLS-DA plot of HRV parameters involving all groups, respectively, with statistical values in the form of regression (R2 0.58). Circles indicate the 95% confidence interval for each class. The LOOCV method is used in cross-validation, using accuracy as a performance measure in the MetaboAnalyst web server. (C&F) represents the VIP scores of ECG and HRV in decreasing order of their respective VIP score values. G1, G2 and G3 indicate control, CUS-VEH and CUS-DCN groups, respectively.