Analysis of T wave complexity during arrhythmic phases caused by hemodialysis

The sensitivity of an index based on the principal component analysis (PCA) of the T-wave to the frequency of premature ventricular contractions (PVCs) caused by hemodialysis was investigated. The ECGs from 24 hemodialysis sessions were studied. From the 12-lead Holter recording, the first and the last hours were extracted. The sessions were classified on the basis of the trend of PVC occurrence in the last hour with respect to the first one: no change in PVC occurrence (group A), and increased PVCs (group B). PCA was applied to the T-wave extracted from each beat over leads I, II and VI to V6, so determining the degree of correlation between the eight T-waveforms. The index of complexity (PCA-T), defined as the ratio between the second and the first eigenvalue, was calculated. No difference was found in PCA-T in the first hour of hemodialysis between the two groups (A: 0.16±0.11, B: 0.20±0.08). Hemodialysis caused a significant increase in PCA-T in both group A (to 0.23±0.13, p<0.001) and group B (to 0.33±0.10, p<0.001). However, the increase in PCA-T was significantly higher in group B with respect to group A (0.13±0.05 vs 0.07±0.051 p<0.05). These results show that hemodialysis significantly increases the complexity of the T-wave. Such an increase is greater when a significant increase in the frequency of PVCs occurs