Characteristics of heart rate variability entropy and blood pressure during hemodialysis in patients with end-stage renal disease

Entropy (ENT) is a newly developed measure of the complexity of heart rate variability (HRV). The aim of this study was to characterize the complexity of HRV in patients with end-stage renal disease (ESRD) and to find a possible clinical utility. Healthy subjects and patients with ESRD undergoing hemodialysis (HD) were recruited. The HD population consisted of patients with and without diabetes mellitus (DM). An electrocardiogram was recorded before HD, and blood pressure was measured during HD. The coefficients of variation of R-R intervals, high- and low-frequency components, and ratio of the low- to high-frequency components were measured as variables of HRV. The ENT was used to describe the complexity of HRV. Forty-six healthy subjects and 27 HD patients participated in this study. The ENT negatively correlated with the duration of DM (p = 0.001), systolic blood pressure (p = 0.003), and mean blood pressure (p = 0.004) before a HD session. ENT in HD patients was lower than that in healthy subjects (p < 0.01). ENT in HD patients with DM was lower than that in HD patients without DM (p < 0.01). The change in systolic blood pressure (DeltaSBP) during a HD session showed high correlations to ENT and ultrafiltration rate (UFR) of the dialyzer. The following equation was obtained: DeltaSBP = 2.25 x ENT - 2.28 x UFR - 21.27 (R2 = 0.805; p < 0.0001). ENT decreased with uremic and diabetic status. ENT also represents a possible prediction of hypotension during a HD session.     

Cardiac response to hemodialysis with different cardiovascular tolerance: heart rate variability and QT interval analysis

A therapy-specific worsening of cardiovascular stability during bicarbonate dialysis (BD) with respect to acetate-free biofiltration (AFB) have been previously reported. We further investigated the impact of the 2 therapies on electrocardiographic parameters in order to gain novel insight into the cardiac responses. Holter ECG acquired during hypotension-free sessions (12 BD + 12 AFB) were retrospectively analyzed. R-R intervals were extracted from ECG recordings. An autoregressive spectral technique was used to compute low- and high-frequency (LF and HF) components of heart rate variability (HRV). QT interval duration was measured with a computer-assisted technique and corrected for HR. In BD the LF component of HRV after an initial increase was slowly depressed with respect to AFB (p < 0.05). QT duration showed a significant (p < 0.01) hemodialysis-induced reduction. QT shortening was more pronounced (p < 0.05) in BD than in AFB (-31 vs. -10 ms), even after correction for HR (p < 0.05). Cardiac electrical activity is significantly affected by the hemodialysis technique. The decrease in the LF component of HRV and the QT shortening are coherent with the worse cardiovascular tolerance observed in BD and with the hypothesis of an enhanced production of endogenous nitric oxide.     

Complexity of physiological responses decreases in high-stress musical performance

For musicians, performing in front of an audience can cause considerable apprehension; indeed, performance anxiety is felt throughout the profession, with wide ranging symptoms arising irrespective of age, skill level and amount of practice. A key indicator of stress is frequency-specific fluctuations in the dynamics of heart rate known as heart rate variability (HRV). Recent developments in sensor technology have made possible the measurement of physiological parameters reflecting HRV non-invasively and outside of the laboratory, opening research avenues for real-time performer feedback to help improve stress management. However, the study of stress using standard algorithms has led to conflicting and inconsistent results. Here, we present an innovative and rigorous approach which combines: (i) a controlled and repeatable experiment in which the physiological response of an expert musician was evaluated in a low-stress performance and a high-stress recital for an audience of 400 people, (ii) a piece of music with varying physical and cognitive demands, and (iii) dynamic stress level assessment with standard and state-of-the-art HRV analysis algorithms such as those within the domain of complexity science which account for higher order stress signatures. We show that this offers new scope for interpreting the autonomic nervous system response to stress in real-world scenarios, with the evolution of stress levels being consistent with the difficulty of the music being played, superimposed on the stress caused by performing in front of an audience. For an emerging class of algorithms that can analyse HRV independent of absolute data scaling, it is shown that complexity science performs a more accurate assessment of average stress levels, thus providing greater insight into the degree of physiological change experienced by musicians when performing in public.     

Revisiting Autonomic Dysfunction in End-Stage Renal Disease Patients

Background: Autonomic dysfunction is frequent in end‐stage renal disease (ESRD) patients, but both the relative involvement of the parasympathetic and sympathetic branches and the role of antihypertensive drugs in this setting are still controversial. The present study addressed these issues employing a battery of standard noninvasive cardiovascular autonomic tests. Methods: Sympathetic (S) function was evaluated by responses of both systolic blood pressure (BP) to passive tilting and diastolic BP to handgrip; parasympathetic (P) function, through the respiratory sinus arrhythmia test and the heart rate response to the 4‐s unloaded exercise test. Additional tests influenced by both branches of the autonomic system (P + S) were accomplished by the assessment of heart rate response to the Valsalva maneuver, handgrip, and tilting. Results: Studied subjects belonged to one of the three groups: ESRD patients not requiring BP medications (n = 11; 8 men, 3 women); ESRD patients receiving antihypertensive therapy (n = 36; 21 men, 15 women); and apparently healthy controls (n = 15; 10 men, 5 women). When the variables grouped according to the branch of the autonomic nervous system predominantly probed were analyzed, only the frequency of impaired sympathetic autonomic responses was higher in ESRD patients not receiving BP drugs compared to controls (55 vs. 23%, P = 0.040). In contrast, when ESRD patients receiving BP drugs were compared to controls, the differences became significant in S, P, and P + S tests (46 vs. 23%, P = 0.045; 22 vs. 3%, P = 0.020; and 34 vs. 13%, P = 0.010, respectively). With the criterion of more than one positive finding in any of the variables examined for diagnosing autonomic dysfunction, the prevalence of autonomic dysfunction was 20% in controls, 64% in ESRD patients not receiving BP drugs (P = 0.005 vs. controls), and 67% in ESRD patients receiving BP drugs (P = 0.043 vs. controls). Conclusions: ESRD continues to be associated with a high prevalence of autonomic dysfunction. ESRD patients receiving BP drugs were found to have detectable impairment in the entire autonomic system in contrast to those not receiving BP drugs in whom inadequate responses were restricted to the sympathetic branch.     

Ventricular arrhythmia in dialysis patients: A link with higher hemoglobin levels?

We investigated the frequencies and associated risk factors of cardiac arrhythmias and heart rate variability (HRV) in hemodialysis (HD) patients. One hundred fifty prevalent HD patients underwent 48-hour Holter monitoring. Holter monitoring was analyzed in 4 phases: early post-HD phase (12 hours), late post-HD phase (20 hours), pre-HD phase (12 hours), and HD phase (4 hours). Echocardiography was applied to measure the left ventricular mass index in a subgroup of patients (n: 52). Patients with ventricular premature contraction (VPC) were significantly older, had a longer HD duration, and higher hemoglobin (Hb) levels. Left ventricular mass index was significantly correlated with the frequency of VPC, during the HD and pre HD phases (r: 0.435, 0.312, respectively). In logistic regression analysis, patients with Hb level >11.9 g/dL (high tertile) had a 4.5-fold increased risk of VPC compared with those with Hb levels <10.8 g/dL (P: 0.04). In HRV analysis, age (P<0.001), and diabetes (P: 0.03) were found to be independent predictors of low standard deviation of all mean normal-to-normal RR intervals. Increased left ventricular mass index is associated with a high frequency of VPC in the pre-HD and HD periods. The occurrence of VPC is predicted by older age, longer dialysis duration, and higher Hb levels, while older age and diabetes are the determinants of HRV. The relation between higher Hb levels and the frequency of VPC might provide a clue for the explanation of the detrimental effect of higher Hb levels on HD patients.     

Myocardial stunning in hemodialysis: What is the overall message?

Heart failure and cardiovascular events are common in chronic renal failure. Hemodialysis (HD) causes significant hemodynamic changes and hypotension. New evidence based on intradialytic echocardiography demonstrates transient cardiac dysfunction or stunning in majority of chronic HD patients. Over time, this group may progress to chronic heart failure and appears to predict higher cardiovascular events and mortality. Although the exact etiology is unclear, alterations in HD technique and cardiac medications may reduce this complication. We review the current understanding of acute cardiac stunning during HD and present a systematic management algorithm to optimizing overall outcomes in this high-risk population.     

环境噪声对心脏影响规律的研究方法与实现

文章从工业环境噪声对人体心率影响的角度,研究噪声对人体负荷影响规律的方法及实现问题,并开发数据处理系统。在研究方法中,依据工业企业噪声现状选择声级、频率范围;采用能够反映微小变化的心率变异（HRV）作为评价指标,获得噪声对人体心脏的影响规律。该方法与系统实现强调影响劳动安全的人体心脏负荷问题,可从工程生理学与心理学双重角度更为全面科学地研究噪声的影响规律。     

基于Hilbert-Huang变换的心率变异信号分析

提出一种基于Hilbert-Huang变换(HHT)的心率变异信号分析的新方法。心率变异分析被广泛应用于评估心脏自律功能以及疾病诊断领域。为获得更多心率信号内在特征,首先利用经验模态分解(Empirical Mode Decomposi-tion,EMD)方法将信号分解为一组固有模态函数(Intrinsic Mode Function,IMF),运用Hilbert变换计算并分析各层IMF的瞬时频率和瞬时幅值,从而获取信号所包含的内在信息、心率变异突发时刻和变化趋势。结合积分脉冲频率调制(Inte-gral Pulse Frequency Modulation,IPFM)模型模拟出的心率信号以及真实的心率信号,利用小波分析方法以及HHT方法对心率信号进行对比分析,实验结果证明了HHT方法的可行性,显示了该方法相对于小波分析方法的优势。     

基于HRV非线性特征的心律不齐自动分析

心率变异性(HRV)信号包含大量心脏和心血管系统的生理和病理信息,对其进行深入分析可以帮助诊断和预警心律不齐等心脏疾病.论文利用MIT-BIH心电数据库,提取正常心律和心律不齐两种心电数据并进行信号预处理以消除噪声干扰;采用小波变换提取小波系数的模极值和过零点以得到心电R波信号,计算其一阶差分得到HRV序列.然后,提取...     

Health-related qualıty of lıfe, sleep qualıty, and depressıon in peritoneal dialysis and hemodıalysıs patıents

Health-related quality of life (HRQoL) and sleep quality (SQ) were impaired in patients with end-stage renal disease (ESRD). The impairment of both HRQoL and SQ and being in a depressive mood were found to be associated with increased morbidity and mortality in dialysis patients. We aimed to investigate the association between SQ, HRQoL, and depression, and to define independent predictors of SQ and depression in peritoneal dialysis (PD) and hemodialysis (HD) patients. Ninety HD patients (41 females, 49 males with mean age 50 ± 15.7 years) and 64 PD patients (27 females, 37 males with mean age 52.4 ± 15.3 years) receiving renal replacement therapy for at least 3 months were screened for the assessment of SQ, HRQoL, and depression in this cross-sectional study. A modified postsleep inventory, Short Form of Medical Outcomes Study (SF-36) and Beck depression inventory (BDI) were applied to all patients for evaluating SQ, HRQoL, and depression, respectively. HD and PD patients had similar total SQ scores. Physical and mental component scale of HRQoL were found to be significantly higher in HD patients (p < 0.001). PD patients were found to be much more in depressive mood when compared with HD patients (p < 0.001). Independent predictors of depression in patients were mental component scale of HRQoL, gender (being female), and dialysis modality (being PD patient). Physical component scale was also found to be an independent predictor of SQ. This study showed that despite similar SQ scores between two groups, HD patients had better HRQoL and less depression than PD patients.     

Categorization of the hemodynamic response to hemodialysis: The importance of baroreflex sensitivity

Intradialytic hypotension (IDH) remains an important cause of morbidity and mortality in hemodialysis (HD) patients. The baroreflex arc is under autonomic control and regulates blood pressure. This study aimed to investigate the contribution of impaired baroreflex sensitivity (BRS) to the pathophysiology of IDH. Thirty-four chronic HD (12 IDH-prone, 22 IDH-resistant) patients underwent BRS measurement during HD with relative blood volume monitoring. During analysis, patients were separated into four age-matched groups according to resting BRS≥4.5 ms/mmHg and hemodynamic stability. Resting BRS was extremely heterogenous (geometric mean BRS 5.78±1.41 [range 1.76–41.41] ms/mmHg). Relative blood volume reduction was well matched in all groups (mean reduction in relative blood volume for all patients −6.74%±0.86%, P>0.05). Thirty-seven episodes of IDH occurred in the IDH prone, reduced BRS group. Patients with impaired resting BRS and prone to IDH had markedly different responses to HD as compared to the preserved BRS group, but the total peripheral resistance response was significantly lower than in the IDH-resistant patients (15.9%±2.1% vs. 42.4%±3.0%, respectively, P<0.001). In those patients prone to IDH and with impaired resting BRS, percentage reduction in cardiac output at the end of HD highly correlated with reduction in relative blood volume (r=0.94, P=0.006). Hypotension during dialysis may be an important source of recurrent cardiac injury and early recognition of those patients prone to relative symptomatic and asymptomatic hypotension remains important. Impaired resting BRS and recognition of a suboptimal peripheral pressor response, appear to predict those patients most likely to undergo hemodynamic instability and may assist in the pursuit of this elusive goal.     

Left ventricular morphology and function in diabetic and nondiabetic hemodialyzed patients

Morbidity in end-stage renal disease (ESRD) diabetic patients is worse than in patients without diabetes mellitus (DM). This study aims to compare clinical, laboratory, and echocardiographic features between the ESRD patients with and without DM. Fifty-eight ESRD patients on dialysis were prospectively divided into two groups according to the presence of DM. Demographic, clinical, laboratory, and echocardiographic features (ejection fraction and wall motion score index) were compared between the two groups. Overall, 20 out of 58 patients (37.8%) with ESRD had DM. There were no significant differences between the patients with DM and those without DM when it comes to age (60.6 ± 10.6 vs. 59.0 ± 10.6 years, P = 0.665), ejection fraction (52.6% ± 12.8% vs. 54.2% ± 12.8%, P = 0.59), and wall motion score index (1.21 ± 0.3 vs.1.15 ± 0.3, P = 0.37). In multivariant analysis of the interventricular septum, posterior wall thickness and left atrium size correlated positively with DM. There was also no statistical difference in myocardial perfusion disturbances on real-time contrast echocardiography between the groups with and without DM (12 (60%) patients vs. 14 patients (36.8%), P = 0.079). Among diabetics 77.8% had significant atherosclerotic changes, while in the group without DM, only 38.1%, P = 0.01. From the laboratory parameters ferritin and high-sensitivity C-reactive protein levels were significantly higher in the group with DM, P = 0.014 and P = 0.026, respectively. Patients with ESRD and DM have significantly bigger left atrial size, thicker left ventricular walls, and higher serum ferritin and high-sensitivity C-reactive protein levels than the patients without DM. The aforementioned features may be possible risk factors for the development of adverse cardiac events in patients on hemodialysis.     

Outcomes of patients with end‐stage renal disease (ESRD) under chronic hemodialysis requiring continuous renal replacement therapy (CRRT) and patients without ESRD in acute kidney injury requiring CRRT: A single‐center study

In most continuous renal replacement therapy (CRRT) studies, end‐stage renal disease (ESRD) patients were excluded and the outcomes of patients with ESRD treated with chronic hemodialysis (HD) were unknown. The purposes of this study were to (1) evaluate short‐term patient survival and (2) compare the survival of conventional HD patients needing CRRT with the survival of non‐ ESRD patients in acute kidney injury (AKI) requiring CRRT. We evaluated adults (>18 years) requiring CRRT who were treated in the intensive care unit (ICU) at Kosin University Gospel Hospital from January 1, 2009 to December 31, 2010. A total of 100 (24 ESRD, 76 non‐ESRD) patients underwent CRRT during the study period. Patients were divided into two major groups: patients with ESRD requiring chronic dialysis and patients without ESRD (non‐ESRD) with AKI. We compared the survival of conventional HD patients requiring CRRT with the survival of non‐ ESRD patients in AKI requiring CRRT. For non‐ESRD patients, the 90‐day survival rate was 41.6%. For ESRD patients, the 90‐day survival rate was 55.3%. Multivariate Cox proportional hazards analyses demonstrated that conventional HD was not a significant predictor of mortality (hazard ratio [HR]: 0.334, 95% confidence interval [CI]: 0.063–1.763, P = 0.196), after adjustment for age, gender, presence of sepsis, APACHE score, use of vasoactive drugs, number of organ failures, ultrafiltration rate, and arterial pH. The survival rates of non‐ESRD and ESRD patients requiring CRRT did not differ; ESRD with conventional HD patients may be not a significant predictor of mortality.     

Platelet‐to‐lymphocyte ratio better predicts inflammation than neutrophil‐to‐lymphocyte ratio in end‐stage renal disease patients

Neutrophil‐to‐lymphocyte ratio (NLR) was introduced as a potential marker to determine inflammation in end‐stage renal disease (ESRD) patients. Recently, platelet‐to‐lymphocyte ratio (PLR) and NLR were found to positively correlated with inflammatory markers including tumor necrosis factor‐α (TNF‐α) and interleukin (IL)‐6 in cardiac and noncardiac patients. Data regarding PLR and its association with inflammation are lacking in hemodialysis (HD) and peritoneal dialysis (PD) patients. Hence, we aimed to determine the relationship between PLR, NLR, and inflammation in ESRD patients. This was a cross‐sectional study involving 62 ESRD patients (29 females, 33 males; mean age, 49.6 ± 14.6 years) receiving PD or HD for ≥6 months in the Dialysis Unit of Necmettin Erbakan University. PLR, NLR, C‐reactive protein, TNF‐α, IL‐6 levels were measured. PLR, NLR, serum high sensitive C‐reactive protein, IL‐6, and TNF‐α levels were significantly higher in PD patients when compared with HD patients. ESRD patients with PLR ≥ 140 had significantly higher NLR, IL‐6, and TNF‐α levels when compared to patients with PLR < 139. In the bivariate correlation analysis, PLR was positively correlated with NLR, IL‐6, and TNF‐α in this population. When we compared the association of PLR and NLR with IL‐6 (r = 0.371, P = 0.003 vs. r = 0.263, P = 0.04, respectively) and TNF‐α (r = 0.334, P = 0.008 vs. r = 0.273, P = 0.032, respectively), PLR was found to be superior to NLR in terms of inflammation in ESRD patients. Simple calculation of PLR can predict inflammation better than NLR in ESRD patients.     

On the quantification of heart rate variability spectral parameters using time-frequency and time-varying methods

In the last decades, one of the main challenges in the study of heart rate variability (HRV) signals has been the quantification of the low-frequency (LF) and high-frequency (HF) components of the HRV spectrum during non-stationary events. At this regard, different time-frequency and time-varying approaches have been proposed with the aim to track the modification of the HRV spectra during ischaemic attacks, provocative stress testing, sleep or daily-life activities. The quantitative evaluation of power (and frequencies) of the LF and HF components has been approached in various ways depending on the selected time-frequency method. This paper is an excursus through the most common time-frequency/time-varying representation of the HRV signal with a special emphasis on the algorithms employed for the reliable quantification of the LF and HF parameters and their tracking.     

Daily dialyses decrease plasma levels of brain natriuretic peptide (BNP), a biomarker of left ventricular dysfunction

Brain natriuretic peptide or B-type natriuretic peptide (BNP) is a sensitive marker of heart disease. Plasma levels of BNP increase in left ventricular failure and determination of plasma BNP has become a useful tool in the diagnosis of heart failure. Hemodialysis (HD) patients may have elevated plasma levels of BNP, particularly predialysis, that correlate with echocardiographic signs of left ventricular dysfunction. High BNP levels are also a strong predictor of mortality in both nonrenal and HD patients. We studied plasma BNP levels in patients who changed from conventional thrice-weekly dialysis to daily dialysis 6 times a week while maintaining a total weekly time on dialysis of 12 hr. Twelve HD patients, mean age 55 years, had 4 hr of conventional thrice-weekly treatment for 4 weeks. Predialysis and postdialysis blood samples were obtained at the last dialysis. Patients were then dialyzed for 2 hr, 6 times weekly, for 4 weeks (daily dialysis). Again, predialysis and postdialysis blood samples were collected at the last HD. Brain natriuretic peptide plasma concentrations were determined by immunoradiometric assay. Predialysis BNP levels decreased from 194+/-51 ng/L (68+/-19 pmol/L; mean+SE) during thrice-weekly HD to 113+/-45 ng/L (41+/-18 pmol/L; p = 0.001) after 4 weeks on daily dialysis. With thrice-weekly HD, predialysis BNP levels were higher than postdialysis levels: 120+/-26 ng/L (39+/-8 pmol/L; p = 0.059). With daily dialysis, predialysis BNP levels did not differ significantly from postdialysis levels. Elevated predialysis plasma levels of BNP, considered sensitive and early markers of left ventricular dysfunction, decreased when patients were changed from conventional thrice-weekly HD to daily dialysis maintaining total hours of dialysis per week constant. Given the accumulated evidence that BNP is a biomarker of left ventricular dysfunction and can be used for risk stratification and guidance in pharmacotherapy of heart failure, daily dialysis appears to lead to less cardiac distress.     

Lethal cardiac arrhythmia during central venous catheterization in a uremic patient: A case report and review of the literature

Double‐lumen central venous catheter (CVC) is a rapid access technique for hemodialysis (HD) when an arteriovenous fistula or graft is not available. A variety of procedure‐related complications have been reported, such as infection and pneumothorax, but serious cardiac complications are relatively less mentioned. We report a uremic woman with preexisting left bundle branch block who required emergent HD and received jugular double‐lumen CVC insertion, which was complicated by short‐duration ventricular tachycardia followed by complete atrio‐ventricular block and bradycardia. Pharmacological management did not reverse heart rate and rhythm. External pacing was not applied because she remained hemodynamically stable in the course of HD. Heart rate returned to sinus rhythm with left bundle branch block 4 hours later and did not recur through the whole admission period. We speculate that the transient arrhythmia might have been induced by mechanical contact with the ventricular wall during the procedure with the guided metallic wire. In conclusion, physicians responsible for CVC catheterization should pay more attention to patients with preexisting cardiac arrhythmia to prevent such technical mistakes from transpiring.     

基于多因素噪声模糊综合评价方法的研究及应用

以往的噪声评价是基于A声级进行的，缺乏对人的心理和除听力以外的其它生理因素的考虑。因此，文章在传统的噪声评价研究的基础上，建立具有创新意义的由听力损失、心率变异和脑波组成的多因素噪声模糊评价系统，进行噪声对人体负荷综合影响的评价。经过标准噪声人机实验的验证分析，得到结论：多因素的评价方法较传统方法更符合实际影响情况。     

心率变异性在手控交会对接操作脑力负荷评价中的应用

目的研究心率变异性指标用于脑力负荷评价的可行性,并对其在手控交会对接脑力负荷评价中的应用进行分析讨论。方法实验研究以手控交会对接操作为主任务,使用心率变异性来表征脑力负荷水平的变化。对8名志愿者进行了两个阶段共6轮的训练,每轮训练由10个共包含了高、中、低难度水平的操作单元组成。通过比较志愿者在两个阶段的关键绩效指标和心率变异性指标,分析心率变异性指标用于脑力负荷评价的有效性。结果在不同的操作难度、训练程度和操作阶段之间,部分心率变异性指标表现出了较强的敏感性,随着训练程度和操作阶段的变化,其敏感性强度也存在一定的差异。结论实验结果表明心率变异性指标可以用于脑力负荷评价,随着训练程度的提高,脑力负荷水平逐渐降低;随着单次操作过程中由前到后的变化,脑力负荷水平逐渐降低。