Multivariate analysis of TU wave complex on electrocardiogram in Andersen–Tawil syndrome with KCNJ2 mutations

BACKGROUND: The exact differences between the TU wave complex of ATS1 and that of healthy individuals remain to be investigated. We sought to characterize the TU wave complex of Andersen–Tawil syndrome type 1 (ATS1) using high frequency electrocardiogram (ECG) data. METHODS: Electrocardiograms were recorded as time series data with a 2 kHz frequency ECG amplifier in 13 patients with ATS1 (positive for KCNJ2 mutation, ATS1 group) and age‐matched healthy individuals (control group). Conventional ECG parameters were measured, and principal component analysis (PCA) and independent component analysis (ICA) were applied to the TU wave complex. RESULTS: Time from T peak (Tp) to U peak (Up), time from bottom (B) to Up, and time from B to U end (BUe, U duration) (0.232 ± 0.018 vs. 0.165 ± 0.017, p < .0001), where B is the lowest point between T and U waves, were all longer in the ATS1 group than the control group. Multivariate logistic regression analysis revealed that BUe could completely differentiate the two groups. PCA ratios in the ATS1 group were significantly larger than the control group (26.5 ± 12.3 vs. 10.4 ± 6.2, p = .0005). ICA revealed 1 or 2 U‐wave‐specific independent components (ICs) that exclusively comprise the U wave in ATS1, whereas U waves in the control group were composed of some ICs that also comprised T waves. CONCLUSIONS: U‐wave‐related temporal parameters, particularly BUe, and the existence of U‐wave‐specific ICs, extracted in the ICA, are useful for differentiation of U waves in ATS1 from those in healthy individuals.