## 3 Results
### HRV Indices  
Regarding temporal indices, Figure 5a shows the results for patient F1020 (Class 1) and describes the changes in the SDNN index (blue line) with notable variations over time, as the RMSSD index (red line) over the 48 h; marking the beginning and end of the hemodialysis session vertical dotted lines were added. Figure 5b shows the changes over the 48 h of recording for the LF/HF ratio, also for patient F1020, where the beginning and end of the hemodialysis session are vertical dotted lines. In Figure 5c, for patient F1017, changes in HRV are seen due to hemodialysis. Even though, in the interdialytic period, similar changes and decreases were observed, they were not reported extensively. After the three groups in Section 3.3 were established, the hypothesis that the hour with the highest number of PVCs would correspond to the period of greatest risk was taken up again, and the HRV indices calculated in blocks of 5 min were selected, considering women and men separately. The purpose of this stage was to determine whether the stratification of patients based on the behavior of the PVCs during the 48 h of recording can be associated with a higher risk based on the decrease in HRV indices. For Classes 1, 2, and 3, a dynamic HRV vector was constructed, composed of 14 elements corresponding to the analyses carried out in blocks of 5 min with an overlap of 0.77 min. The analysis results corresponding to the group of women were concentrated in Table 4 and for men in Table 5. These dynamic vectors describe the behavior of the indices during the analyzed hour, which, in this proposal, focuses on analyzing the changes in the HRV indices in the hour with the largest number of PVCs of the 48 h record. The seven HRV indices proposed can differentiate, with statistical significance, the three classes analyzed. The mean values for Class 1 are SDNN = 22.63 ms, RMSSD = 6.87 ms, LF = 421.35 ms\({}^{2}\), HF = 91.58 ms\({}^{2}\), LF/HF ratio = 3.52, SD1 = 4.86 ms, and SD2 = 31.56 ms.  
For Class 2, the average values are SDNN = 25.72 ms, RMSSD = 5.39 ms, LF = 177.70 ms\({}^{2}\), HF = 66.33 ms\({}^{2}\), the LF/HF ratio = 2.68, SD1 = 3.82 ms, and SD2 = 36.13 ms.  
For Class 3, the mean values are SDNN = 13.91 ms, RMSSD = 4.82 ms, LF = 175.26 ms\({}^{2}\), HF = 70.59 ms\({}^{2}\), LF/HF ratio = 2.54, SD1 = 3.12 ms, and SD2 = 19.32 ms.  
A statistically significant difference was found among the three classes, denotating that the dynamic vectors describing the behavior of each class contribute to the characterization of the presence of PVCs for each pattern. These patterns can help stratify patients to improve their monitoring and possibly their treatment. Figure 4: Patient 1051; 5 min segment, composed of approximately 450 samples. Artifacts, which are mostly identified PVCs, are corrected by replacing them with the average of the nearest valid intervals, ensuring a continuous and physiologically plausible signal for HRV analysis. Figure 5: Changes in HRV indices over 48 h in patient F1020. (**a**) In the domain of time, the blue line represents the SDNN index (left scale), and the red line represents the RMSSD index (right scale). The dotted vertical lines indicate the start and end of the hemodialysis session. More pronounced variability is seen in SDNN compared to RMSSD. (**b**) The red line represents the evolution of the LF/HF index over time. A progressive increase in the LF/HF index is observed. (**c**) Patient 1017, hourly distribution of PVCs, and changes in overall variability (SDNN index). The analysis does not show a clear pattern directly relating PVC presence with HRV. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & \multicolumn{8}{c}{**Women Population**} \\ \hline  & & \multicolumn{8}{c}{**HRV Indices**} \\ \cline{3-8}  & **Block No. ** & \begin{tabular}{c} **SDNN** \\ **[ms]** \\ \end{tabular}  & \begin{tabular}{c} **RMSSD** \\ **[ms]** \\ \end{tabular}  & \begin{tabular}{c} **LF** \\ **[ms\({}^{2}\)]** \\ \end{tabular}  & \begin{tabular}{c} **HF** \\ **[ms\({}^{2}\)]** \\ \end{tabular}