Electrocardiogram abnormalities and heart rate variability in predicting mortality and cardiovascular events among hemodialyzed patients

Predictive value of heart rate variability on long-term mortality in end-stage kidney disease on hemodialysis

Autonomic disturbance is common in end-stage kidney disease (ESKD). Heart rate variability (HRV) is a useful tool to assess autonomic function. We aimed to evaluate the predictive value of HRV on all-cause mortality and explore the proper timing of HRV assessment. This prospective cohort study enrolled 163 ESKD on hemodialysis patients from April-December 2018. HRV measurements were recorded ten minutes before hemodialysis, four hours during hemodialysis, and ten minutes after hemodialysis. Clinical parameters and all-cause mortality were recorded. Cox-proportional hazard regression was used for statistical analysis. After a median follow up of 40 months, 37 (22.7%) patients died. Post-dialysis HRV parameters including higher very low frequency (VLF) (hazard ratio [HR], 0.881; 95%confidence interval [CI], 0.828-0.937; p<0.001), higher normalized low frequency (nLF) (HR, 0.950; 95%CI, 0.917-0.984; p = 0.005) and higher LF/HF ratio (HR, 0.232; 95%CI, 0.087-0.619; p = 0.004) were the independent predictors associated with lower risk for all-cause mortality. Higher post-dialysis normalized high frequency (nHF) increased risk of mortality (HR, 1.051; 95%CI, 1.015-1.089; p = 0.005). HRV parameters at pre-dialysis and during dialysis were not predictive for all-cause mortality. The area under receiver operating characteristic curve (AuROC) of VLF for survival was highest compared to other HRV parameters at post-dialysis period (AuROC 0.71; 95% CI; 0.62-0.79; p<0.001). In conclusion, post-dialysis HRV parameters predicted all-cause mortaliy in ESKD. VLF measured at post-dialysis exhibited best predictive value for survival in chronic hemodialysis patients.

Neuropathy - Exponent of Accelerated Involution in Uremia: The Role of Carbamylation

Premature loss of functional integrity of the nervous system in chronic renal failure (CRF) as a consequence of persistent biological activities of the general uremic milieu is almost identical to its structural and functional involution during the process of physiological ageing, but disproportionate and independent of chronological age. In the hyperuremic status of CRF (urea - carbamide), forced carbamylation, as a non-enzymatic post-translational modification (NEPTM) of proteins and amino acids, by changing their biological properties and decreasing proteolysis capacity, represents pathogenetic potential of intensified molecular ageing and accelerated, pathological involution. Physiological predisposition and the exposure of neuropathy before complications of other organs and organ systems in CRF, due to the simultaneous and mutually pathogenetically related uremic lesion and the tissue and vascular segment of the nervous system, direct interest towards proteomic analytical techniques of quantification of carbamylated products as biomarkers of uremic neurotoxicity. Hypothetically, identical to the already established applications of other NEPTM products in practice, they have the potential of clinical methodology in the evaluation of uremic neuropathy and its contribution to the general prediction, but also to the change of the conventional CRF classification. In addition, the identification and therapeutic control of the substrate of accelerated involution, responsible for the amplification of not only neurological but also general degenerative processes in CRF, is attractive in the context of the well-known attitude towards aging.

Cardiac arrhythmia during early-week and mid-week dialysis in hemodialysis patients

Data on cardiac arrhythmia and electrolyte changes during the dialysis cycle have been limited. Fifty-two hemodialysis (HD) patients underwent 48-h Holter monitoring during early-week and mid-week HD sessions. Pre-HD and post-HD blood samples were collected in both HD sessions. The 48-h Holter data were divided into five phases: (1) 4-h during the early-week HD (HD1), (2) 12-h post-HD1, (3) 16-h period between Phases 2 and 4 (used as the patient's baseline electrocardiography [ECG]), (4) 12-h pre-HD2 phase, and (5) 4-h during the mid-week HD (HD2). The patients' mean age was 68.54 ± 13.37 years. We found that the dialysate-to-serum[K] gradient and changes of S[K] were significantly higher in HD1 than in HD2, as well as changes of S[Mg]. There were no significant ECG changes during the 4-h HD1 and HD2 when compared with the baseline ECG. Phase 2 of Holter ECG was the most common phase that showed significant changes (increased QT interval dispersion (QTD), increased ventricular events, increased number of premature ventricular contractions, ST elevation and ST depression), which was contributed from the dialysate[K] 2 mmol/L subgroup, but not the dialysate[K] 3 mmol/L subgroup. In the subgroup of patients with a high ultrafiltration rate (UFR; mean UFR ≥10 mL/kg/h), there were significantly increased ventricular events and ST-segment changes in Phase 2. In conclusion, ECG changes were associated with the dialysis cycle, significantly in the 12-h after early-week HD sessions. These may be associated with low dialysate[K] or high dialysate-to-S[K] gradient, high ultrafiltration rate and duration of the interdialytic interval.

Changes in acoustic cardiographic parameters before and after hemodialysis are associated with overall and cardiovascular mortality in hemodialysis patients

Acoustic cardiography can provide simultaneous electrocardiography and acoustic cardiac data to assess the electronic and mechanical heart functions. The aim of this study was to assess whether changes in acoustic cardiographic parameters (ACPs) before and after hemodialysis (HD) are associated with overall and cardiovascular (CV) mortality in HD patients. A total of 162 HD patients was enrolled and ACPs were measured before and after HD, including left ventricular systolic time (LVST), systolic dysfunction index (SDI), third (S3) and fourth (S4) heart sounds, and electromechanical activation time (EMAT). During a follow-up of 2.9 years, 25 deaths occurred with 16 from CV causes. Multivariate analysis showed that high △SDI (per 1; hazard ratio [HR], 2.178; 95% confidence interval [CI], 1.189–3.990), high △EMAT (per 1%; HR, 2.218; 95% CI 1.382–3.559), and low △LVST (per 1 ms; HR, 0.947; 95% CI 0.912–0.984) were independently associated with increased overall mortality. In addition, high △EMAT (per 1%; HR, 2.141; 95% CI 1.117–4.102), and low △LVST (per 1 ms; HR, 0.777; 95% CI 0.637–0.949) were associated with increased CV mortality. In conclusion, the changes in ACPs before and after HD may be a useful clinical marker and stronger prognostic marker of overall and CV mortality than ACPs before HD.

Heart Rate Variability and Prognosis in Hemodialysis Patients: A Meta-Analysis

BACKGROUND

Heart rate variability (HRV) means the variation in time of beat-to-beat interval. Lower HRV has been shown to be related with death and cardiovascular events in previous studies. In the last few years, the number of patients with ESRD has increased steadily. Maintenance hemodialysis is the most prevalent renal replacement therapy in patients with ESRD. This study aims to investigate if decreased HRV is an independent predictor of mortality in maintenance hemodialysis patients.

METHODS

Pubmed/Medline, EMBASE, Ovid, the Web of Science, and the Cochrane Central Register of Controlled Trials databases were searched up to October 1, 2019, for full-text articles in English. Cohort studies reporting the association between HRV and prognosis in hemodialysis patients were selected. Data extraction was performed by 2 reviewers independently, with adjudication by a third reviewer. Extracted data included the study characteristics, HRV measurement and research outcomes. Hazard ratios (HRs) and 95% confidence interval (CI) were pooled in a random-effects model for outcomes of all-cause and cardiovascular mortality. Heterogeneity assessment, subgroup analyses, and sensitivity analysis were conducted.

RESULTS

A total of 7 studies were eligible. HRV metrics consist of SDNN, SDANN, RMSSD, pNN50, HRVTI, ULF, VLF, LF, HF, LF/HF ratio, HRT, DC, and scaling exponents α1 and α2. Decreased HRV was associated with higher all-cause mortality (HR: 1.63, 95% CI: 1.11-2.39, p = 0.014) and cardiovascular mortality (HR: 1.07, 95% CI: 1.00-1.15, p = 0.045). Among the different HRV metrics, decreased SDANN (p < 0.001) and decreased LF/HF ratio (p = 0.001) were identified as predictors of all-cause death. Decreased SDNN, SDANN, and LF/HF ratio were identified as predictors of cardiovascular death (p = 0.004, p = 0.001, and p = 0.002).

CONCLUSIONS

Decreased HRV is associated with higher risk of all-cause and cardiovascular death in the hemodialysis population. Decreased SDANN and LF/HF were identified as predictors of both all-cause and cardiovascular mortality, while the utility of other HRV metrics requires further investigation. The protocol for this study was registered with PROSPERO (CRD42019141886).

Associations of long-term exposure to ambient air pollution with cardiac conduction abnormalities in Chinese adults: The CHCN-BTH cohort study

BACKGROUND

Evidence regarding the effects of long-term and high-level ambient air pollution exposure on cardiac conduction systems remains sparse.

OBJECTIVES

To investigate the associations of long-term exposure to air pollution and cardiac conduction abnormalities in Chinese adults and explore the susceptibility characteristics.

METHODS

In 2017, a total of 27,047 participants aged 18-80 years were recruited from the baseline survey of the Cohort Study on Chronic Disease of Communities Natural Population in Beijing, Tianjin and Hebei (CHCN-BTH). The three year (2014-2016) average pollutant concentrations were assessed by a spatial statistical model for PM_2.5 and air monitoring stations for PM₁₀, SO₂, NO₂, O₃ and CO. Residential proximity to a roadway was calculated by neighborhood analysis. Associations were estimated by two-level generalized linear mixed models. Stratified analyses related to demographic characteristics, health behaviors, and cardiometabolic risk factors were performed. Two-pollutant models were used to evaluate the possible role of single pollutants.

RESULTS

We detected significant associations of long-term air pollutant exposure with increased heart rate (HR), QRS and QTc, such that an interquartile range increase in PM_2.5 was associated with 3.63% (95% CI: 3.07%, 4.19%), 1.21% (95% CI: 0.83%, 1.60%), and 0.13% (95% CI: 0.07%, 0.18%) changes in HR, QRS and QTc, respectively. Compared to the other pollutants, the estimates of PM_2.5 remained the most stable across all two-pollutant models. Similarly, significant associations were observed between living closer to a major roadway and higher HR, QRS and QTc. Stratified analyses showed generally greater association estimates in older people, males, smokers, alcohol drinkers, and those with obesity, hypertension and diabetes.

CONCLUSIONS

Long-term exposure to ambient air pollution was associated with cardiac conduction abnormalities in Chinese adults, especially in older people, males, smokers, alcohol drinkers, and those with cardiometabolic risk factors. PM_2.5 may be the most stable pollutant to reflect the associations.

The potential of electrocardiography for cardiac risk prediction in chronic and end-stage kidney disease

Cardiovascular mortality is very high in chronic and end-stage kidney disease (ESKD). However, risk stratification data are lacking. Sudden cardiac deaths are among the most common cardiovascular causes of death in these populations. As a result, many studies have assessed the prognostic potential of various electrocardiographic parameters in the renal population. Recent data from studies of implantable loop recordings in haemodialysis patients from five different countries have shed light on a pre-eminent bradyarrhythmic risk of mortality. Importantly, heart block addressed by permanent pacing system was detected in a proportion of patients during the prolonged recording periods. Standard electrocardiogram is inexpensive, non-invasive and easily accessible. Hence, risk prediction models using this simple investigation tool could easily translate into clinical practice. We believe that electrocardiographic assessment is currently under-valued in renal populations. For this review, we identified studies from the preceding 10 years that assessed the use of conventional and novel electrocardiographic biomarkers as risk predictors in chronic and ESKD. The review indicates that conventional electrocardiographic markers are not reliable for risk stratification in the renal populations. Novel parameters have shown promising results in smaller studies, but further validation in larger populations is required.

Reproducibility of Hemodynamic, Cardiac Autonomic Modulation, and Blood Flow Assessments in Patients with Intermittent Claudication

BACKGROUND

The aim of this study is to identify, in patients with peripheral artery disease and intermittent claudication (IC), the reproducibility of heart rate (HR), blood pressure (BP), rate pressure product, heart rate variability (HRV), and forearm and calf blood flow (BF) and vasodilatory assessments.

METHODS

Twenty-nine patients with IC underwent test and retest sessions, 8-12 days apart. During each session, HR, BP, HRV, BF, and vasodilatory responses were measured by electrocardiogram, auscultation, spectral analysis of HRV (low frequency, LF_R-R; high frequency, HF_R-R), and strain gauge plethysmography (baseline BF, post-occlusion BF, post-occlusion area under the curve). Reproducibility was determined by intra-class correlation coefficient (ICC), typical error, coefficient of variation (CV), and limits of agreement.

RESULTS

The ICC for HR and BP was >0.8 with CV <9%. For most HRV measures, ICC was >0.9 while CV was <7%, except for LF/HF (ICC = 0.737, CV = 93.8%). The ICC for forearm and calf baseline BF assessments was >0.9 while CV was <19%; variable ICC and CV for vasodilatory responses were exhibited for calf (0.653-0.770, 35.2-37.7%) and forearm (0.169-0.265, 46.2-55.5%).

CONCLUSIONS

In male patients with IC, systemic hemodynamics (HR and BP), cardiac autonomic modulation (LF_R-R and HF_R-R), and forearm and calf baseline BF assessments exhibited excellent reproducibility, whereas the level of reproducibility for vasodilatory responses were moderate to poor. Assessment reproducibility has highlighted appropriate clinical tools for the regular monitoring of disease/intervention progression in patients with IC.

Association between PR interval prolongation and electro-anatomical substrate in patients with atrial fibrillation

Background

Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical routine. Left atrial (LA) electro-anatomical remodelling in AF patients indicates disease progression and is associated with poor therapeutic success. PR interval prolongation is associated with an increased risk for AF, however, the association between LA remodelling measured as low voltage areas (LVA) during catheter ablation and PR interval is unknown. The aim of this study was to investigate the association between PR interval prolongation and LVA in AF patients.

Methods

We studied 103 patients (62±12 years, 59% males, 34% persistent AF) undergoing first AF catheter ablation and presenting with sinus rhythm. PR interval prolongation was defined as PR >200ms and analysed in resting ECG before intervention. LVA were determined using high-density maps and defined as <0.5 mV.

Results

There were 24 patients (23%) with PR interval prolongation and 18 patients (17%) with LVA. There were significant correlations between PR prolongation with LVA, CHA₂DS₂-VASc score and eGFR (r² = 0.230, 0.216, and 0.307, all p<0.05). PR interval prolongation (OR 3.450, p = 0.024), persistent AF (OR 5.391, p = 0.002), and LA size (OR 1.117, p = 0.018) were significant predictors for LVA, while age (OR 1.072, p = 0.005), LVA (OR 3.450 p = 0.024) and eGFR (OR 0.962, p = 0.004) were associated with PR interval prolongation.

Conclusions

Beside persistent AF and LA size, PR interval prolongation might be useful for the prediction of electro-anatomical substrate in AF patients. Larger studies are needed to confirm these results.

Effects of Marine n-3 Polyunsaturated Fatty Acids on Heart Rate Variability and Heart Rate in Patients on Chronic Dialysis: A Randomized Controlled Trial

Marine n-3 polyunsaturated fatty acids (PUFA) may improve autonomic dysfunction, as indicated by an increase in heart rate variability (HRV) and reduce the risk of sudden cardiac death. Hence, the aim of this study was to investigate the effects of marine n-3 PUFA on 24-h HRV in patients on chronic dialysis, who have a high risk of sudden cardiac death. Between June 2014 and March 2016, 112 patients on chronic dialysis from Denmark were allocated to a daily supplement of 2 g marine n-3 PUFA or control for three months in a randomized, double-blinded, controlled trial. A 48-h Holter monitoring was performed and mean 24-h HRV indices for the two days were available in 85 patients. The mean age was 62.3 years (SD: 14.3) and median dialysis vintage was 1.7 years (IQR: 0.5, 6.4). Within-group and between-group changes in outcome were evaluated by a paired and two sample t-test, respectively. Marine n-3 PUFA did not change the primary endpoint SDNN (SD of all RR-intervals) reflecting overall HRV, but other HRV indices increased and the mean RR-interval increased significantly, corresponding to a decrease in heart rate by 2.5 beats per minute (p = 0.04). In conclusion, marine n-3 PUFA did not change SDNN, but the mean heart rate was significantly reduced and changes in other HRV-indices were also observed, indicating an increase in vagal modulation that might be protective against malignant ventricular arrhythmias.

Cardiovascular Autonomic Neuropathy and its Association with Cardiovascular and All-cause Mortality in Patients with End-stage Renal Disease

Background End-stage renal disease frequently leads to increased cardiovascular mortality. Cardiovascular autonomic neuropathy (CAN) may be predictive of cardiac arrhythmias and sudden cardiac death in patients with end-stage renal disease. Methods A total of 70 patients with end-stage renal disease were included in the study. The assessment of cardiac dysautonomia was based on the four standardized tests performed at the baseline and, again, at the end of the study. The criteria for CAN included at least two abnormal test results. Results Fifty of 70 patients completed the study and were followed-up after one year. Out of the 50 patients, 44 (88%) had CAN at baseline. Twelve (24%) patients died at the one-year follow-up. Sudden cardiac death was reported in seven out of 12 (58%) patients. All seven patients who died had high dysautonomia scores (three abnormal tests) at the baseline. There was a significantly higher percentage of patients with all four abnormal tests amongst patients who died of any cause (56% vs. 17%; RR 6.07, 95% CI 1.29-28.49; p-value 0.02) or due to sudden cardiac death (43% vs. 10.5%; RR 6.37, 95% CI 1.03-39.36; p-value 0.04). All five patients who did not have CAN at the baseline developed this abnormality on repeat testing after one year. Conclusion The prevalence of CAN in patients with end-stage renal disease on maintenance hemodialysis was significantly higher. CAN was an independent predictor of all-cause and cardiovascular mortality, which highlights it as a risk stratification tool in patients with end-stage renal disease.

Marine n-3 PUFA, heart rate variability and ventricular arrhythmias in patients on chronic dialysis: a cross-sectional study

Marine n-3 PUFA may improve autonomic dysfunction by an increase in heart rate variability (HRV) and may reduce the risk of malignant ventricular arrhythmias. Only a few smaller studies have examined such effects in patients on chronic dialysis, who often have autonomic dysfunction and a high risk of sudden cardiac death, which accounts for almost 30 % of all deaths. This cross-sectional study investigated the association between the plasma phospholipid content of n-3 PUFA and 24-h HRV or ventricular arrhythmias in patients on chronic dialysis. A 48-h Holter monitoring was performed on 169 patients on in-centre dialysis (83 %), home haemodialysis (10 %) or peritoneal dialysis (7 %) obtaining data on arrhythmias (n 152) and 24-h HRV (n 135). The mean overall HRV (standard deviation of normal intervals (SDNN)) was low and 71 % had a reduced overall HRV (SDNN<100 ms) indicating autonomic dysfunction. No significant associations between plasma phospholipid content of total marine n-3 PUFA, EPA (22 : 5n-3) or DHA (22 : 6n-3) and time-domain or frequency-domain HRV were detected in crude or adjusted linear regression analysis. However, a higher plasma phospholipid content of DHA was associated with a significantly lower proportion of patients with ventricular tachycardia (higher DHA-tertile: 9 % v. lower DHA-tertile: 28 %, P=0·02). In conclusion, the content of marine n-3 PUFA in plasma phospholipids was not associated with 24-h HRV, but a higher plasma phospholipid content of DHA was associated with a lower occurrence of ventricular tachycardia suggesting an antiarrhythmic effect of marine n-3 PUFA in patients on chronic dialysis.

Association between resting heart rate just before starting the first dialysis session and mortality: A multicentre prospective cohort study

AIM

Some observational studies of the general population showed that resting heart rate was associated with mortality. However, the relationship was unclear in dialysis patients.

METHODS

The study was a multicentre prospective cohort analysis including 1102 patients. Patients were classified into four groups based on resting heart rate just before starting the first dialysis session: <60/min; 60-79/min; 80-100/min; and ≥101/min. All-cause mortality, cardiovascular (CV) related mortality, and incidences of CV events after dialysis initiation were compared using the log-rank test. All-cause mortality rates for patients with heart rates <60, 60-79, and ≥101/min were compared to those for patients with heart rates 80-100/min, using multivariate Cox proportional hazard regression analysis. Moreover, we compared the outcomes among patients without use of β-blocker or heart failure symptom at the first dialysis session.

RESULTS

Significant differences were observed in the all-cause mortality rates among the four groups (P = 0.007). Multivariate analysis revealed that all-cause mortality was significantly higher in patients with heart rate ≥ 101/min than in patients with heart rate 80-100/min (hazard ratio [HR] = 2.30, 95% confidence interval [CI]: 1.25-4.23). Subgroup analysis showed that among patients without use of b-blocker or heart failure symptom, all-cause mortality rates for those with heart rates ≥101/min were significantly higher than in patients with heart rate 80-100/min (HR = 2.98, 95% CI: 1.51-5.88, HR = 3.65, 95% CI: 1.59-8.36, respectively).

CONCLUSION

The resting heart rate just before starting the first dialysis session was associated with all-cause mortality after dialysis initiation.

Cardiac Autonomic Neuropathy Predicts All-Cause and Cardiovascular Mortality in Patients With End-Stage Renal Failure: A 5-Year Prospective Study

Introduction

Chronic renal disease is associated with increased cardiovascular (CV) mortality. Cardiac autonomic neuropathy (CAN) is predictive of mortality for diseases that affect the autonomic nervous system. We prospectively evaluated the prognostic value of indexes of left ventricular (LV) function and CAN in all-cause and CV mortality of patients with end-stage renal failure (ESRF).

Methods

A total of 133 patients with ESRF were recruited. LV function was evaluated by echocardiography, whereas cardiac autonomic function was assessed using the battery of the 4 standardized tests proposed by Ewing.

Results

A total of 123 of 133 (92.5%) patients completed the study and were followed for a mean of 4.9 ± 2.6 years. Mean LV ejection fraction (LVEF) was 50.9 ± 6.9%, whereas 70 (57.9%) patients had CAN. Sixty-nine all-cause and 36 CV deaths were recorded. The survival rates at 3, 5, and 7 years were 77.2%, 57.4%, and 33.7%, respectively. Multivariate analysis after adjustment for waist circumference, current smoking, history of diabetes, and coronary artery disease demonstrated that the only independent predictors of all-cause mortality during follow-up were age, serum triglycerides, LVEF, and presence of CAN. Competing risk regression analysis, after adjusting for waist circumference, coronary heart disease, serum glucose, and triglycerides, indicated that age and presence of CAN were independent risk factors for CV mortality.

Discussion

Age and presence of CAN are independent predictors of all-cause and CV mortality in patients with ESRF. The functionality of the cardiac autonomic nervous system activity can be used for the risk stratification in patients with ESRF.

Electrocardiographic Abnormalities and QTc Interval in Patients Undergoing Hemodialysis

Background

Sudden cardiac death is one of the primary causes of mortality in chronic hemodialysis (HD) patients. Prolonged QT_c interval is associated with increased rate of sudden cardiac death. The aim of this article is to assess the abnormalities found in electrocardiograms (ECGs), and to explore factors that can influence the QT_c interval.

Methods

A total of 141 conventional HD patients were enrolled in this study. ECG tests were conducted on each patient before a single dialysis session and 15 minutes before the end of dialysis session (at peak stress). Echocardiography tests were conducted before dialysis session began. Blood samples were drawn by phlebotomy immediately before and after the dialysis session.

Results

Before dialysis, 93.62% of the patients were in sinus rhythm, and approximately 65% of the patients showed a prolonged QT_c interval (i.e., a QT_c interval above 440 ms in males and above 460ms in females). A comparison of ECG parameters before dialysis and at peak stress showed increases in heart rate (77.45±11.92 vs. 80.38±14.65 bpm, p = 0.001) and QT_c interval (460.05±24.53 ms vs. 470.93±24.92 ms, p<0.001). After dividing patients into two groups according to the QT_c interval, lower pre-dialysis serum concentrations of potassium (K⁺), calcium (Ca²⁺), phosphorus, calcium* phosphorus (Ca*P), and higher concentrations of plasma brain natriuretic peptide (BNP) were found in the group with prolonged QT_c intervals. Patients in this group also had a larger left atrial diameter (LAD) and a thicker interventricular septum, and they tended to be older than patients in the other group. Then patients were divided into two groups according to ΔQT_c (ΔQT_c = QT_{c peak-stress}- QT_{c pre-HD}). When analyzing the patients whose QT_c intervals were longer at peak stress than before HD, we found that they had higher concentrations of Ca²⁺ and P⁵⁺ and lower concentrations of K⁺, ferritin, UA, and BNP. They were also more likely to be female. In addition, more cardiac construction abnormalities were found in this group. In multiple regression analyses, serum Ca²⁺ concentration before HD and LAD were independent variables of QT_c interval prolongation. UA, ferritin, and interventricular septum were independent variables of ΔQT_c.

Conclusion

Prolonged QT interval is very common in HD patients and is associated with several risk factors. An appropriate concentration of dialysate electrolytes should be chosen depending on patients’ clinical conditions.

The influence of inhaled multi-walled carbon nanotubes on the autonomic nervous system

Background

Heart rate and cardiovascular function are regulated by the autonomic nervous system. Heart rate variability (HRV) as a marker reflects the activity of autonomic nervous system. The prognostic significance of HRV in cardiovascular disease has been reported in clinical and epidemiological studies. The present study focused on the influence of inhaled multi-walled carbon nanotubes (MWCNTs) on autonomic nervous system by HRV analysis.

Methods

Male Sprague–Dawley rats were pre-implanted with a telemetry device and kept in the individual cages for recovery. At week four after device implantation, rats were exposed to MWCNTs for 5 h at a concentration of 5 mg/m³. The real-time EKGs were recorded by a telemetry system at pre-exposure, during exposure, 1 day and 7 days post-exposure. HRV was measured by root mean square of successive differences (RMSSD); the standard deviation of inter-beat (RR) interval (SDNN); the percentage of successive RR interval differences greater than 5 ms (pNN5) and 10 ms (pNN10); low frequency (LF) and high frequency (HF).

Results

Exposure to MWCNTs increased the percentage of differences between adjacent R-R intervals over 10 ms (pNN10) (p < 0.01), RMSSD (p < 0.01), LF (p < 0.05) and HF (p < 0.01).

Conclusions

Inhalation of MWCNTs significantly alters the balance between sympathetic and parasympathetic nervous system. Whether such transient alterations in autonomic nervous performance would alter cardiovascular function and raise the risk of cardiovascular events in people with pre-existing cardiovascular conditions warrants further study.