Effects of Orthostatism and Hemodialysis on Mean Heart Period and Fractal Heart Rate Properties of Chronic Renal Failure Patients

Abstract

The aim of this work was to evaluate the short-term fractal index (α ) of heart rate variability (HRV) in chronic renal failure (CRF) patients by identifying the effects of orthostatism and hemodialysis (HD), and by evaluating the correlation between α and the mean RR interval from sinus beats (meanNN). HRV time series were derived from ECG data of 19 CRF patients and 20 age-matched healthy subjects obtained at supine and orthostatic positions (lasting 5 min each). Data from CRF patients were collected before and after HD. α was calculated from each time series and compared by analysis of variance. Pearson's correlations between meanNN and α were calculated using the data from both positions by considering three groups: healthy subjects, CRF before HD and CRF after HD. At supine position, α of CRF patients after HD (1.17 ± 0.30) was larger (P < 0.05) than in healthy subjects (0.89 ± 0.28) but not before HD (1.10 ± 0.34). α increased (P < 0.05) in response to orthostatism in healthy subjects (1.29 ± 0.26) and CRF patients after HD (1.34 ± 0.31), but not before HD (1.25 ± 0.37). Whereas α was correlated (P < 0.05) with the meanNN of healthy subjects (r = -0.562) and CRF patients after HD (r = -0.388), no significance in CRF patients before HD was identified (r = 0.003). Multiple regression analysis confirmed that α was mainly predicted by the orthostatic position (in all groups) and meanNN (healthy subjects and patients after HD), showing no association with the renal disease condition in itself. In conclusion, as in healthy subjects, α of CRF patients correlates with meanNN after HD (indicating a more irregular-like HRV behavior at slower heart rates). This suggests that CRF patients with stable blood pressure preserve a regulatory adaptability despite a shifted setting point of the heart period (i.e., higher heart rate) in comparison with healthy subjects.

Cardiac Autonomic Response to Active Standing in Calcific Aortic Valve Stenosis

“…Yet, both allowed us to identify that the dynamic behavior of heart rate fluctuations in these patients is also modified. NAV subjects showed larger anti-correlated behavior at supine position (see α 1sign in Table 4 ) and only for these people did we find significant increments in both α 1 and α 1sign (i.e., larger regularity and less anti-correlation) as would be expected by the active standing maneuver [ 24 , 25 ]. An anti-correlated behavior of heart rate fluctuations can be attributed to a condition in which a modulating factor (e.g., the parasympathetic activity) exerts a dominant effect, whereas less anti-correlation is manifested when various regulatory factors participate [ 43 , 44 ].…”

“…In response to the orthostatic stimulus, the vagal response decreases and the sympathetic one becomes more important, which is manifested by a HRV reduction showing a predominance of low-frequency over high-frequency oscillations [ 21 , 22 ]. This HRV reduction caused by the orthostatic challenge also introduces a distinctive dynamical change in such oscillations [ 23 , 24 , 25 ]. To characterize this behavior, the so-called scaling indices can be used [ 26 , 27 ], which quantify the fractal-like HRV irregularity along different time scales.…”

Association between Mean Heart Rate and Recurrence Quantification Analysis of Heart Rate Variability in End-Stage Renal Disease

“…As an example, the short-term fractal index (α1) has a significant correlation with the mean heart rate in healthy people [ 24 , 25 ]. Although such correlation is lost in ESRD patients before hemodialysis, it is recovered after hemodialysis and so considered as an indicator of cardiovascular adaptability [ 24 , 26 ] as well as a potential marker to differentiate between adaptive changes to achieve a precise demand response and long-term adjustments for facing pathophysiological alterations that, in other physiological contexts, could be deleterious. During an orthostatic challenge, the change from a supine to standing up position modifies some RQA indices [ 11 ].…”

Sudden Cardiac Death in Dialysis: Arrhythmic Mechanisms and the Value of Non-invasive Electrophysiology

“…Interestingly, whilst active standing was associated with increase in normalized LF and decrease in normalized HF during HD treatment, this was not the case when treatment with hemofiltration was used. Echeverria et al (2017) showed an increase in LF/HF in response to postural provocations before and after HD treatment.…”