Impact of metabolic syndrome and its components on heart rate variability during hemodialysis: a cross-sectional study

Abstract

Background: Both uremia and metabolic syndrome (MetS) affect heart rate variability (HRV) which is a risk factor of poor prognoses. The aim of this study was to evaluate the impact of MetS on HRV among chronic hemodialysis patients.

Methods: This cross-sectional study was carried out in a teaching hospital in Northern Taiwan from June to August, 2010. Adult patients on chronic hemodialysis without active medical conditions were enrolled. HRV were measured for 4 times on the index hemodialysis day (HRV-0, -1, -2, and -3 at before, initial, middle, and late phases of hemodialysis, respectively), and the baseline demographic data and clinical parameters during the hemodialysis session were documented. Then we evaluated the impacts of MetS and its five components on HRV.

Results: One hundred and seventy-five patients (100 women, mean age 65.1 ± 12.9 years) were enrolled and included those with MetS (n = 91, 52 %) and without MetS (n = 84, 48 %). The patients with MetS(+) had significantly lower very low frequency, total power, and variance in HRV-0, total power and variance in HRV-2, and variance in HRV-3. (all p ≦ 0.05) When using the individual components of MetS to evaluate the impacts on HRV indices, the fasting plasma glucose (FPG) criterion significantly affected most indices of HRV while other four components including "waist circumference", "triglycerides", "blood pressure", and "high-density lipoprotein" criteria exhibited little impacts on HRV. FPG criterion carried the most powerful influence on cardiac ANS, which was even higher than that of MetS. The HRV of patients with FPG(+) increased initially during the hemodialysis, but turned to decrease dramatically at the late phase of hemodialysis.

Conclusions: The impact of FPG(+) outstood the influence of uremic autonomic dysfunction, and FPG criterion was the most important one among all the components of MetS to influence HRV. These results underscored the importance of interpretation and management for abnormal glucose metabolism.

Fig. 1

Plots comparing heart rate variability indices during hemodialysis among the four groups. a VLF, b LF, c HF, d TP, e Var, f LF/HF. red solid line FPG(+), n =  65; blue solid line FPG(-), n = 110; red dashed line FPG(+)/MetS(+), n = 54; red dotted line FPG(+)/MetS(-), n = 11; blue dashed line FPG(-)/MetS(+), n = 37; blue dotted line FPG(-)/MetS(-), n = 73. HRV-1, -2, and -3 were HRV measured at initial, middle, and late phase of the HD session, respectively. #, ##, ### denote p ≤ 0.05, ≤0.01, ≤0.001, respectively, between FPG(+) and FGP(-) groups. *, **, *** denote p ≤ 0.05, ≤0.01, ≤0.001, respectively, between two subgroups. Blue and red arrow lines respectively denote the trend of serial change of HRV in FPG(-) and FPG(+) groups. ^$ denotes p ≤ 0.001. Units: Ln(ms2) in VLF, LF, HF, TP, and Var; Ln(ratio) in LF/HF ratio. FPG fasting plasma glucose, HF high frequency; HRV heart rate variability, LF low frequency, MetS metabolic syndrome, TP total power, Var variance of the R-R intervals, VLF very low frequency