Heart rhythm complexity as predictors for the prognosis of end-stage renal disease patients undergoing hemodialysis

Abstract

Background: Heart rhythm complexity, a measure of heart rate dynamics and a risk predictor in various clinical diseases, has not been systematically studied in patients with end-stage renal disease. The aim of this study is to investigate the heart rhythm complexity and its prognostic value for mortality in end-stage renal disease patients undergoing hemodialysis.

Methods: To assess heart rhythm complexity and conventional heart rate variability measures, 4-h continuous electrocardiography for a retrospective cohort of 202 ostensibly healthy control subjects and 51 hemodialysis patients with end-stage renal disease were analyzed. Heart rhythm complexity was quantified by the complexity index from the measurement of the multiscale entropy profile.

Results: During a follow-up of 13 months, 8 people died in the patient group. Values of either traditional heart rate variability measurements or complexity indices were found significantly lower in patients than those in healthy controls. In addition, the complexity indices (Area 1-5, Area 6-15 and Area 6-20) in the mortality group were significantly lower than those in the survival group, while there were no significant differences in traditional heart rate variability parameters between the two groups. In receiver operating characteristic curve analysis, Area 6-20 (AUC = 0.895, p < 0.001) showed the strongest predictive power between mortality and survival groups.

Conclusion: The results suggest that heart rhythm complexity is impaired for patients with end-stage renal disease. Furthermore, the complexity index of heart rate variability quantified by multiscale entropy may be a powerful independent predictor of mortality in end-stage renal disease patients undergoing hemodialysis.

Keywords: Autonomic nervous system; Complexity; End-stage renal disease; Heart rate variability; Multiscale entropy.

Fig. 1

The sample entropy over different time scales. The orange square open symbols represented the entropy of patients with ESRD, and the light blue open circles the entropy of healthy control subjects. The green open squares represented the entropy of the survival group after session hemodialysis treatment, and the pink solid squares the entropy of the mortality group after session hemodialysis treatment. Symbols represent the mean values of entropy for each group and bars represent the standard error ($\mathit{SE}=\mathit{SD}/\sqrt{n}$, where n is the number of subjects). *p < 0.05, **p < 0.01, and ***p < 0.001 for comparison between groups

Fig. 2

Analysis of the discrimination power of the survival and mortality by receiver operating characteristic (ROC) curve analysis. The areas under the curve of Area 1–5, Area 6–15 and Area 6–20 were 0.858, 0.892 and 0.895, respectively

Fig. 3

Kaplan-Meier survival curves (P < 0.001) for all-cause mortality according to the the MSE parameters Area 6–20. The mortality for Area 6–20 ≥ 13.43 and Area 6–20 < 13.43 were 4.80 and 66.7%, respectively