Increased QT interval dispersion after hemodialysis: role of peridialytic electrolyte gradients

Advanced Interatrial Block across the Spectrum of Renal Function

Background and Objective: Interatrial block (IAB) is defined as a conduction delay between the right and left atria. No data are available about the prevalence of both partial IAB and advanced IAB among the different stages of chronic kidney disease. The aim of this study was to describe the prevalence and type of advanced IAB across the spectrum of renal function, including patients on dialysis and the clinical characteristics associated with advanced IAB. Materials and Methods: Retrospective, single-center study of 151 patients consecutively admitted to the Nephrology and Ophthalmology Unit for 3 months. The study population was divided into three groups according to stages of chronic kidney disease. We evaluated the prevalence and pattern of IAB among the groups and the clinical characteristics associated with advanced IAB. Results: The prevalence of partial IAB was significantly lower in end-stage kidney disease (ESKD) group compared to control group (36.7% vs. 59.6%; p = 0.02); in contrast the prevalence of advanced IAB was significantly higher in both chronic kidney disease (CKD) (17.8% vs. 5.3%, p = 0.04) and ESKD group (24.5% vs. 5.3%, p = 0.005) compared to control group. The atypical pattern of advanced IAB was more frequent in both the ESKD and CKD group than in the control group (100% and 75% vs. 33.3%; p = 0.02). Overall, among patients that showed advanced IAB, 17 (73.9%) showed an atypical pattern by morphology and 2 (8.7%) showed an atypical pattern by duration of advanced IAB. The ESKD group was younger than the control group (65.7 ± 12.3 years vs. 71.3 ± 9.9 years; p = 0.01) and showed a higher prevalence of beta blockers (42.9% vs. 19.3%; p = 0.009), as in the CKD group (37.8% vs. 19.3%; p= 0.04). Conclusions: The progressive worsening of renal function was associated with an increasing prevalence of advanced IAB. Advanced IAB may be a sign of uremic cardiomyopathy and may suggest further evaluation with long-term follow-up to investigate its prognostic significance in chronic kidney disease.

Effect of dialysate bicarbonate and sodium on blood pH in maintenance hemodialysis-A prospective study

INTRODUCTION

The validity of adjusting dialysate bicarbonate based on pre-hemodialysis (HD) serum bicarbonate is unclear. There are no studies of the impact of dialysate sodium on blood pH.

AIMS

To understand the impact of dialysate bicarbonate and sodium on blood pH.

METHODS

Two hundred arterialized blood samples were obtained on the third session of HD with four configurations of dialysate: sodium (140, 137 mEq/L) and bicarbonate (38, 32 mEq/L).

RESULTS

The correlation between pre-HD serum bicarbonate and pH was modest (r = 0.6). A lower dialysate sodium (p = 0.035) and a higher bicarbonate (p = 0.02) associated with a higher post-HD blood pH. The frequency of pre-HD blood pH of <7.4 and a post-HD blood pH of >7.5 did not differ for samples with serum bicarbonate <22, 22-26, or >26 mEq/L.

DISCUSSION/CONCLUSIONS

Adjusting dialysate buffer based on pre-HD serum bicarbonate is unnecessary. A higher bicarbonate and lower dialysate sodium associate with post-HD alkalemia.

QT-Prolonging Antibiotics, Serum-to-Dialysate Potassium Gradient, and Risk of Sudden Cardiac Death Among Patients Receiving Maintenance Hemodialysis

Rationale & Objective

Treatment with certain QT interval-prolonging antibiotics is associated with a higher risk of sudden cardiac death among individuals with hemodialysis-dependent kidney failure. Concurrent exposure to large serum-to-dialysate potassium gradients, which promote large potassium shifts, may augment the proarrhythmic effects of these medications. The primary objective of this study was to examine whether the serum-to-dialysate gradient modifies the cardiac safety of azithromycin, and separately, levofloxacin/moxifloxacin.

Study Design

Retrospective observational cohort study using a new-user study design.

Setting & Population

Adult in-center hemodialysis patients with Medicare coverage in the US Renal Data System (2007-2017).

Exposure

Initiation of azithromycin (or levofloxacin/moxifloxacin) as compared to amoxicillin-based antibiotics (exposure). Serum-to-dialysate potassium gradient (effect modifier). Individual patients could contribute multiple study antibiotic treatment episodes to the analyses.

Outcomes

Sudden cardiac death (14 days).

Analytical Approach

Inverse probability of treatment-weighted survival models to estimate HRs and robust 95% CIs.

Results

The azithromycin versus amoxicillin-based antibiotic cohort included 89,379 unique patients with 113,516 azithromycin and 103,493 amoxicillin-based treatment episodes. Azithromycin versus amoxicillin-based antibiotic treatment was associated with a higher risk of sudden cardiac death overall, HR, 1.68; 95% CI, 1.31-2.16. The risk was numerically higher when the baseline serum-to-dialysate potassium gradient was ≥3 mEq/L compared with <3 mEq/L (HR, 2.22; 95% CI, 1.46-3.40 vs HR, 1.43; 95% CI. 1.04-1.96, P _interaction = 0.07). Analogous analyses in a respiratory fluoroquinolone (levofloxacin/moxifloxacin) versus amoxicillin-based antibiotic cohort with 79,449 unique patients and 65,959 respiratory fluoroquinolone and 103,776 amoxicillin-based treatment episodes yielded similar results.

Limitations

Residual confounding.

Conclusions

Although treatment with azithromycin and, separately, respiratory fluoroquinolones were each associated with a heightened risk of sudden cardiac death, this risk was augmented in the setting of larger serum-to-dialysate potassium gradients. Minimizing the potassium gradient may be an approach to reduce the cardiac risk of these antibiotics.

Risk Assessment for Arrhythmia in Pediatric Renal Transplant Recipients

OBJECTIVES

Renal transplant recipients are at risk for ventricular arrhythmia and sudden death. To assess that risk, we compared the ventricular repolarization markers of pediatric renal transplant recipients with those of healthy children.

MATERIALS AND METHODS

We included 30 children and adolescents who were followed for at least 6 months after renal transplant; 30 age- and sex-matched children were included for the control group. Demographic features, medications, and laboratory findings were recorded. Blood pressure measurements, ventricular repolarization indexes including QT dispersion, corrected QT dispersion, T-wave peak-to-end interval dispersion, the T-wave peak-to-end interval∕QT ratio, the T-wave peak-to-end interval∕corrected QT ratio, left ventricular mass index, and relative wall thickness were compared between groups. In addition, the correlations of ventricular repolarization indexes with other variables were evaluated.

RESULTS

Blood pressure standard deviation scores, the mean heart rate, QT dispersion, corrected QT dispersion, the T-wave peak-to-end interval∕QT ratio, the T-wave peak-to-end interval/corrected QT ratio, left ventricular mass index, and relative wall thickness values were significantly higher in renal transplant patients, whereas T-wave peak-to-end interval dispersion, ejection fraction, and fractional shortening were similar between groups. Although ventricular repolarization indexes were similar in patients with and without left ventricular hypertrophy, only corrected QT dispersion was significantly higher in patients with hypertension (P = .006). The only variable that significantly predicted prolonged corrected QT dispersion was the systolic blood pressure standard deviation score (P = .005, β = .403).

CONCLUSIONS

Ventricular repolarization anomalies, hypertension, left ventricular hypertrophy, and cardiac geometry irregularity may be observed after renal transplant in pediatric recipients despite acceptable allograft functions and normal serum electrolyte levels. Control of systolic blood pressure would decrease the risk of ventricular repolarization abnormalities, namely, the corrected QT dispersion. Follow-up of cardiovascular risks with noninvasive methods is recommended in all pediatric renal transplant recipients.

The modifying effect of the serum-to-dialysate potassium gradient on the cardiovascular safety of SSRIs in the hemodialysis population: a pharmacoepidemiologic study

BACKGROUND

Hypokalemia is a risk factor for drug-induced QT-prolongation. Larger serum-to-dialysate potassium gradients during hemodialysis may augment the proarrhythmic risks of selective serotonin reuptake inhibitors (SSRIs).

METHODS

We conducted a cohort study using 2007-2017 data from the United States Renal Data System and a large dialysis provider to examine if the serum-to-dialysate potassium gradient modifies SSRI cardiac safety. Using a new-user design, we compared 1-year sudden cardiac death (SCD) risk among hemodialysis patients newly treated with higher (citalopram, escitalopram) vs. lower (fluoxetine, fluvoxamine, paroxetine, sertraline) QT-prolonging potential SSRIs, overall and stratified by baseline potassium gradient (≥4 vs. <4 mEq/L). We used inverse probability of treatment weighted survival models to estimate weighted hazard ratios (HRs) and 95% confidence intervals (CIs), and conducted a confirmatory nested case-control study.

RESULTS

The study included 25,099 patients: 11,107 (44.3%) higher QT-prolonging potential SSRI new-users and 13,992 (55.7%) lower QT-prolonging potential SSRI new-users. Overall, higher vs. lower QT-prolonging potential SSRI use was not associated with SCD, weighted HR of 1.03 (95% CI, 0.86-1.24). However, a greater risk of SCD was associated with higher vs. lower QT-prolonging potential SSRI use among patients with baseline potassium gradients ≥4 mEq/L, but not among those with gradients <4 mEq/L, weighted HR of 2.17 (95% CI, 1.16-4.03) vs. 0.95 (0.78-1.16). Nested case-control analyses yielded analogous results.

CONCLUSIONS

The serum-to-dialysate potassium gradient may modify the association between higher vs. lower QT-prolonging SSRI use and SCD among people receiving hemodialysis. Minimizing the potassium gradient in the setting of QT-prolonging medication use may be warranted.

The effects of peritoneal dialysis on QT interval in ESRD patients

BACKGROUND

Patients with chronic kidney disease (CKD) are at a high risk of fatal arrhythmias. The extended corrected QT (QTc) interval is a hallmark of ventricular arrhythmias and sudden cardiac death. Previous studies have shown that QT interval and QTc are prolonged with the decline in renal function. However, there were no available results for patients with peritoneal dialysis (PD). In this study, we examined changes in QT interval and QTc in patients with end-stage renal disease (ESRD) who underwent peritoneal dialysis.

METHODS

A total of 66 ESRD patients who received PD, including 50 males and 16 females, with an average age of 43.56 ± 15.15 years, were enrolled. The follow-up lasted 1 year. The demographics and the etiology of patients were recorded. QTc and clinical/biochemical indexes before dialysis and at 6 and 12 months were determined and analyzed. Dialysis adequacy and peritoneal transport function were assessed in each patient. Analysis of variance (ANOVA), least significant difference (LSD) or Tamhane's T2, Paired T-test, Chi-square test, multiple linear regression analysis, and Pearson correlation coefficient were used to analyze the data. P < 0.05 was considered as statistically significant.

RESULTS

With reference to etiology, 37 patients (56.06%) had chronic nephritis, and 11 (16.67%) had diabetic nephropathy. Most of the peritoneal transport functions were low average transport (25, 37.88%), while the least were high transport (2, 3.03%).During the follow-up period, all patients had adequate peritoneal dialysis. Compared with a baseline before dialysis, anemia, low albumin, blood pressure, blood urea nitrogen, creatinine, uric acid, potassium, calcium, phosphorus, and parathyroid hormone improved after 6 and 12 months, while the residual renal function gradually decreased during the follow-up. The mean QTc of all patients was stable during the follow-up period. According to gender, the QTc in males and female patients were similar. Before PD, diastolic blood pressure, calcium concentration, and hemoglobin level were negatively correlated with QTc in end-stage renal disease patients; After PD, the observed clinical indexes were no longer relevant to QTc.

CONCLUSION

Unlike hemodialysis-induced QTc prolongation, PD did not increase the patient's QT interval and QTc interval, which suggested that myocardial electrical activity might be more stable in patients with adequate peritoneal dialysis.

Epicardial adipose tissue and risk of arrhythmia in nephrotic syndrome

BACKGROUND

Patients with nephrotic syndrome (NS) are at a high risk of cardiovascular disease, obesity, and dyslipidemia. The aim of this study was to evaluate the formation of epicardial adipose tissue (EAT) and investigate electrocardiographic (ECG) parameters in patients.

METHODS

Thirty-two patients aged 0-18 years and 15 control patients were compared. In the patient group, physical examination and laboratory parameters were recorded. Atrial depolarization and ventricular repolarization parameters in ECG were compared between the groups. EAT was evaluated with M-mode measurements on echocardiography.

RESULTS

There was no difference between the groups in terms of sex, age, body mass index, systolic and diastolic BP. EAT was found to be significantly higher in the patient group. In ECG evaluations it was determined that atrial depolarization and ventricular repolarization parameters increased in the patient group.

CONCLUSIONS

Cardiovascular morbidity and mortality are high in kidney diseases. Measurement and follow-up of EAT and ECG findings as a noninvasive parameter can provide information in NS.

Predictive factors of poor blood collecting flow during leukocyte apheresis for cellular therapy

Leukocyte apheresis is necessary in various cellular therapies. However, maintenance of a stable flow rate during leukocyte apheresis is often difficult, even in patients or donors without major problems. Despite this, predictive methods and evidence regarding the reality of the situation are limited. We conducted a retrospective analysis involving adult patients who required leukocyte apheresis for the treatment of neoplasms using WT1-pulsed dendritic cell vaccine. Monocytes were separated from apheresis products to obtain dendritic cells. All the patients were pre-evaluated based on laboratory and chest X-ray findings and subjected to an identical apheresis procedure. The occurrence of poor blood collecting flow during leukocyte apheresis was monitored, and the frequency, clinical information, and associated risk factors were analyzed. Among 160 cases, poor blood collecting flow was observed in 53 cases (33.1%) in a median time of 54 min (range, 2-127 min) post-initiation of leukocyte apheresis. Owing to difficulty in obtaining higher collecting flow, a longer procedure time was required, and in some cases, the scheduled apheresis cycles could not be completed. Consequently, the number of harvested monocytes was low. Multivariable analysis indicated that female patients have an increased risk of poor inlet flow rate. Furthermore, prolonged QT dispersion (QTD) calculated using Bazett's formula was found to be a risk factor. Although the patients did not present any major problems during leukocyte apheresis, poor blood collecting flow was observed in some cases. Sex and pre-evaluated QTD might be useful predictors for these cases; however, further prospective evaluation is necessary.

Heart Rate Variability and Electrocardiographic Parameters Predictive of Arrhythmias in Dogs with Stage IV Chronic Kidney Disease Undergoing Intermittent Haemodialysis

Simple Summary

Monitoring the cardiovascular system plays an important role in this treatment to detect cardiovascular repercussions in dogs with chronic kidney disease (CKD) treated with intermittent haemodialysis (IHD). This study aimed to describe the time-domain and frequency-domain heart rate variability indexes, P and QT dispersions and electrocardiographic alterations observed in dogs with Stage IV CKD undergoing IHD. Animals were divided into three groups, control (10 healthy dogs), clinical treatment (10 dogs with CKD IV submitted to clinical treatment) and IHD (10 dogs with CKD IV submitted to clinical treatment and to dialysis treatment). Clinical, laboratory, HRV indexes and electrocardiographic parameters, as well as QT and P-wave dispersions, were assessed in both CKD groups, prior to and after the end of each clinical treatment/IHD session during the first three sessions. Dogs with CKD IV undergoing IHD had clinically important electrolyte imbalances, electrocardiographic findings, such as the occurrence of arrhythmias and increases in possible predictive parameters for arrhythmias. HRV indexes were better in IHD group, and haemodialysis was more effective at reducing levels of creatinine, urea and phosphorus when compared to intravenous fluid therapy treatment.

Abstract

Intermittent haemodialysis (IHD) is used in dogs with chronic kidney disease (CKD) to reduce azotaemia. Monitoring the cardiovascular system plays an important role in this treatment to detect cardiovascular repercussions. Heart rate variability (HRV) and dispersions of the QT interval and P wave are important markers for mortality risk in humans. This study aimed to describe the time-domain and frequency-domain heart rate variability indexes, P and QT dispersions and electrocardiographic alterations observed in dogs with Stage IV CKD undergoing IHD. Thirty dogs of both sexes, of varying ages and breeds, and weighing between 15 and 30 kg were used. Animals were divided into three groups, control (10 healthy dogs), clinical treatment (10 dogs with CKD IV submitted to clinical treatment twice a week) and IHD (10 dogs with CKD IV submitted to clinical treatment and to dialysis treatment with intermittent haemodialysis twice a week). Clinical, laboratory, HRV indexes and electrocardiographic parameters, as well as QT and P-wave dispersions, were assessed in both CKD groups, prior to and after the end of each clinical treatment/IHD session during the first three sessions. Dogs with CKD IV undergoing IHD had clinically important electrolyte imbalances, primarily hypokalaemia, and pertinent electrocardiographic findings, such as the occurrence of supraventricular arrhythmias and increases in possible predictive parameters for arrhythmias. In spite of these observations, HRV indexes were better in animals undergoing haemodialysis and, in addition, IHD was more effective at reducing levels of creatinine, urea and phosphorus compared to intravenous fluid therapy treatment.

Electrophysiological insights into the relationship between calcium dynamics and cardiomyocyte beating function in chronic hemodialysis treatment

For patients in which the Ca²⁺ concentration of dialysis fluid is lower than that in plasma, chronic hemodialysis treatment often leads to cardiac beating dysfunction. By applying these conditions to an electrophysiological mathematical model, we evaluated the impact of body fluid Ca²⁺ dynamics during treatment on cardiomyocyte beating and, moreover, explored measures that may prevent cardiomyocyte beating dysfunction. First, Ca²⁺ concentrations in both plasma and interstitial fluid were decreased with treatment time, which induced both a slight decline in beating rhythm on a sinoatrial nodal cell and a wane in contraction force on a ventricular cell. These simulated results were in agreement with clinical observations. Next, a relationship between the intracellular Ca²⁺ concentration and ion current dynamics of ion transporters were examined to elucidate the mechanism underlying cardiomyocyte beating dysfunction. The inward current of the Na/Ca exchanger (NCX) increased with a decrease in Ca²⁺ concentration in interstitial fluid and induced a reduction in intracellular Ca²⁺ concentration during treatment. Furthermore, the decline in intracellular Ca²⁺ concentration reduced the contraction force. These findings implied that ion transport through the NCX is a dominant factor that induces cardiomyocyte beating dysfunction during hemodialysis. Finally, the replenishment of Ca²⁺ or application of an NCX inhibitor during treatment suppressed the decrease in intracellular Ca²⁺ concentration and contributed to the stabilization of cardiomyocyte beating function. In summary, the clinical implementation of hepatically cleared NCX inhibitor may be a suitable approach to improving the quality of life for patients on chronic hemodialysis.

A simple modification of dialysate potassium: its impact on plasma potassium concentrations and the electrocardiogram

Background

Sudden death is frequent in haemodialysis (HD) patients. Both hyperkalaemia and change of plasma potassium (K) concentrations induced by HD could explain this. The impact of increasing dialysate K by 1 mEq/L on plasma K concentrations and electrocardiogram (ECG) results before and after HD sessions was studied.

Methods

Patients with pre-dialysis K >5.5 mEq/L were excluded. ECG and K measurements were obtained before and after the first session of the week for 2 weeks. Then, K in the dialysate was increased (from 1 or 3 to 2 or 4 mEq/L, respectively). Blood and ECG measurements were repeated after 2 weeks of this change.

Results

Twenty-seven prevalent HD patients were included. As expected, a significant decrease in K concentrations was observed after the dialysis session, but this decrease was significantly lower after the switch to an increased dialysate K. The pre-dialysis K concentrations were not different after changing, but post-dialysis K concentrations were higher after switching (P < 0.0001), with a lower incidence of post-dialysis hypokalaemia. Regarding ECG, before switching, the QT interval (QT) dispersion increased during the session, whereas no difference was observed after switching. One week after switching, post-dialysis QT dispersion [38 (34-42) ms] was lower than post-dialysis QT dispersion 2 weeks and 1 week before switching [42 (38-57) ms, P = 0.0004; and 40 (35-50) ms, P = 0.0002].

Conclusions

A simple increase of 1 mEq/L of K in the dialysate is associated with a lower risk of hypokalaemia and a lower QT dispersion after the dialysis session. Further study is needed to determine if such a strategy is associated with a lower risk of sudden death.

Cardiovascular Risk in Hemodialysis Patients: A Mechanistic Approach

A new formula is proposed to express the excess burden of cardiovascular risk faced by hemodialysis patients as a function of various inherent, acquired and potentially modifiable factors. The proposed equation CVRHD = CVRB X f(([CKD+HD]/[HDtech+Dr])+X) includes the terms: CVRHD (cardiovascular risk in hemodialysis patients); CVRB (baseline cardiovascular risk); CKD (risk associated with chronic kidney disease); HD (risks associated with the process of hemodialysis); HDtech (benefits of new hemodialysis technologies); Dr (benefits of drug therapies) and X (unknown or putative factors influencing cardiovascular morbidity).

We review the various factors included in this proposed formula, touching upon the epidemiology, pathophysiology and therapeutic implications, including possible strategies to modify risk. As is apparent from the formula, CKD and HD in particular act as risk multipliers in augmenting or amplifying the baseline cardiovascular risk, while new hemodialysis technologies may provide an opportunity for “cardioprotective dialysis.” Drug treatment may serve to mitigate some of the risk unique to this population.

New options for the management of chronic hyperkalemia

Hyperkalemia is a frequently detected electrolyte abnormality that can cause life-threatening complications. Hyperkalemia is most often the result of intrinsic (decreased glomerular filtration rate; selective reduction in distal tubule secretory function; impaired mineralocorticoid activity; and metabolic disturbances, such as acidemia and hyperglycemia) and extrinsic factors (e.g., drugs, such as renin-angiotensin-aldosterone system inhibitors, and potassium intake). The frequent use of renin-angiotensin-aldosterone system inhibitors in patients who are already susceptible to hyperkalemia (e.g., patients with chronic kidney disease, diabetes mellitus, or congestive heart failure) contributes to the high incidence of hyperkalemia. There is a need to understand the causes of hyperkalemia and to be aware of strategies addressing the disorder in a way that provides the most optimal outcome for affected patients. The recent development of 2 new oral potassium-binding agents has led to the emergence of a new paradigm in the treatment of hyperkalemia.

Hemodialysis-induced repolarization abnormalities on ECG are influenced by serum calcium levels and ultrafiltration volumes

PURPOSE

Hemodialysis (HD) patients are known to have high cardiovascular mortality rate. Sudden cardiac death (SCD) due to arrhythmias causes most of the cardiac deaths. HD per se may lead to ECG abnormalities and ventricular arrhythmias. Monitoring ECG parameters such as corrected QT interval, QT dispersion (QTd), Tpe interval may be useful to stratify the patients with high risk of arrhythmia and SCD. Herein we aimed to investigate the effects of changes in serum electrolyte levels and pH on ECG parameters before and after the HD.

METHODS

A total of 50 chronic HD patients (mean age 58 ± 19; male 27) were enrolled. Patients with unmeasurable T waves; atrial fibrillation; bundle branch block; use of class I or class III antiarrhythmic drugs were excluded. Serum potassium, magnesium, calcium, urea, creatinine and pH were measured before and after HD treatment. Standard surface 12-lead ECGs were recorded before and after HD. QTc, QTd, Tpe, JT interval, P-wave-duration, P-wave dispersion were determined.

RESULTS

Serum potassium and magnesium decreased, and calcium, pH and bicarbonate levels increased; QRS and Tpe interval were increased after HD. Basal Tpe was correlated with urea (r = 0.31, p = 0.02). Tpe interval was higher in hypocalcemic compared to normocalcemic patients (77 ± 11 vs 70 ± 9 ms, p = 0.02). ∆Tpe was correlated with ∆calcium (r = -0.32, p = 0.02). Basal QTc was correlated with calcium (r = -0.62, p < 0.001). ∆QTc was correlated with basal calcium (r = 0.39, p = 0.005) and ∆calcium (r = -0.46, p < 0.001). Basal JT was correlated with calcium (r = -0.55, p < 0.001). ∆JT was correlated with pH (r = 0.35, p = 0.01), ∆calcium (r = -0.53, p < 0.001) and ∆magnesium (r = -0.30, p = 0.03). Before HD, 12 patients (12%) were hypermagnesemic of whom JT intervals were lower (314 ± 20 vs 332 ± 23 ms, p = 0.02). Ultrafiltration per body weight was associated with ∆QTc (r = -0.40, p = 0.007) and ∆JT (r = -0.36, p = 0.01).

CONCLUSION

QRS and Tpe intervals were increased after HD. Tpe interval was longer in hypocalcemic patients. Change in Tpe was negatively associated with the change in calcium. Ultrafiltration was associated with ∆QTc and ∆JT. Calcium and ultrafiltration seem to be the most important determinants of ECG parameters of HD-induced repolarization abnormalities.

Epidemiology of hyperkalemia: an update

Hyperkalemia represents one of the most important acute electrolyte abnormalities, due to its potential for causing life-threatening arrhythmias. In individuals with normal kidney function hyperkalemia occurs relatively infrequently, but it can be much more common in patients who have certain predisposing conditions. Patients with chronic kidney disease are the most severely affected group, by virtue of their decreased ability to excrete potassium and because they commonly have additional predisposing conditions that often cluster within patients with chronic kidney disease. These conditions include comorbidities (e.g., diabetes mellitus) and the use of various medications, of which the most important are renin-angiotensin-aldosterone system inhibitors (RAASis). Hyperkalemia is associated with increased risk for all-cause mortality and for malignant arrhythmias such as ventricular fibrillation. The increased risk for adverse outcomes is observed even in serum potassium ranges that are often not considered targets for therapeutic interventions. The heightened risk of mortality associated with hyperkalemia is present in all patient populations, even those in whom hyperkalemia occurs otherwise rarely, such as individuals with normal kidney function.

Sudden cardiac death in CKD patients

The risk of sudden cardiac death (SCD) is high in chronic kidney disease patients, and it increases with the progression of kidney function deterioration. The most common causes of SDC are the following: ventricular tachycardia, ventricular tachyarrhythmia, tachycardia torsade de pointes, sustained ventricular fibrillation and bradyarrhythmia. Dialysis influences cardiovascular system and results in hemodynamic disturbances as well as electrolyte shifts altering myocardial electrophysiology. Studies suggest that this procedure exerts both detrimental (poor volume control can exacerbate hypertension and left ventricle hypertrophy) and beneficial effects (associated with fluid removal and subsequent decrease in left ventricle stretch). Dialysis-related vulnerability to serious arrhythmias is the result of sudden shifts in fluid status and electrolytes, particularly potassium, which alter the physiological milieu. Also Ca(2+) ions, in which concentration alters during dialysis, are of key importance in the contraction of vascular smooth muscle cells and cardiac myocytes, thus exerting significant effects on hemodynamics. Due to the fact that SCD occurs with similar frequency in peritoneal dialysis and in hemodialysis patients, it seems that end-stage renal disease factors are more important than the specific ones associated with dialysis type. The results of randomized trials suggested that hemodialysis patients may not derive the same benefit of cardiovascular disease therapy including beta-blockers, calcium channel blockers and angiotensin-converting enzyme inhibitors as the general population with normal kidney function. Noninvasive tests used to stratify SCD risk in HD patients have poor positive value, and thus, combining tests including HRV, baroreceptor sensitivity and effectiveness index as well as its function indices and heart rate turbulence should be implemented. There are only few large randomized placebo-controlled trials assessing the influence of cardioprotective medications or implantable cardioverter defibrillator (ICD) implantation in dialysis patients on life quality and survival, and their results are sometimes contradictory. The decision concerning treatment and/or ICD implantation in this group of patients should be made on the basis of careful assessment of individual risk factors. Moreover, due to the high hazard of cardiovascular mortality including SCD in dialysis patients, physicians should concentrate on the early selection of high-risk patients, monitoring them and introduction of preventive measures.

Rationale and design for the Predictors of Arrhythmic and Cardiovascular Risk in End Stage Renal Disease (PACE) study

BACKGROUND

Sudden cardiac death occurs commonly in the end-stage renal disease population receiving dialysis, with 25% dying of sudden cardiac death over 5 years. Despite this high risk, surprisingly few prospective studies have studied clinical- and dialysis-related risk factors for sudden cardiac death and arrhythmic precursors of sudden cardiac death in end-stage renal disease.

METHODS/DESIGN

We present a brief summary of the risk factors for arrhythmias and sudden cardiac death in persons with end-stage renal disease as the rationale for the Predictors of Arrhythmic and Cardiovascular Risk in End Stage Renal Disease (PACE) study, a prospective cohort study of patients recently initiated on chronic hemodialysis, with the overall goal to understand arrhythmic and sudden cardiac death risk. Participants were screened for eligibility and excluded if they already had a pacemaker or an automatic implantable cardioverter defibrillator. We describe the study aims, design, and data collection of 574 incident hemodialysis participants from the Baltimore region in Maryland, U.S.A.. Participants were recruited from 27 hemodialysis units and underwent detailed clinical, dialysis and cardiovascular evaluation at baseline and follow-up. Cardiovascular phenotyping was conducted on nondialysis days with signal averaged electrocardiogram, echocardiogram, pulse wave velocity, ankle, brachial index, and cardiac computed tomography and angiography conducted at baseline. Participants were followed annually with study visits including electrocardiogram, pulse wave velocity, and ankle brachial index up to 4 years. A biorepository of serum, plasma, DNA, RNA, and nails were collected to study genetic and serologic factors associated with disease.

DISCUSSION

Studies of modifiable risk factors for sudden cardiac death will help set the stage for clinical trials to test therapies to prevent sudden cardiac death in this high-risk population.

The effect of different dialysate magnesium concentrations on QTc dispersion in hemodialysis patients

BACKGROUND

Electrolyte changes during dialysis affect corrected QT (QTc) and QTc dispersion (QTcd), a surrogate marker of arrhythmogenicity. The impact of magnesium on QTcd is not clear.

METHODS

Twenty-two stable patients on maintenance hemodialysis were enrolled in this study. Each underwent two consecutive hemodialysis sessions at least 2 days apart, the first against normal magnesium dialysate (with magnesium at 1.8 mg/dL) followed by a low magnesium dialysate (with magnesium at 0.6 mg/dL). Pre- and post-dialysis weights, blood pressure, electrolytes, and 12-lead surface EKG were recorded. The QT interval and the QTcd were calculated before and after dialysis in both sessions.

RESULTS

Of 22 patients, 16 were female. The mean age ± SD was 53.7 ± 18.0 years. The mean change of QTcd (pre- vs. post-dialysis) was 9.5 ms (p = 0.120) and 9.3 ms (p = 0.145) in low and normal magnesium groups, respectively. Using univariate analysis, there was a statistically significant decrease in the mean blood pressure, weight, potassium, magnesium, and QTc interval post-dialysis (compared to pre-dialysis) in both groups (p ≤ 0.049). Post-dialysis concentrations of sodium and calcium were unchanged (compared to pre-dialysis) but bicarbonate increased with both dialysate groups (p < 0.001). The mean change of QTcd was not significant pre- versus post-dialysis by univariate analysis in either group. Multiple linear regression analysis adjusting for pertinent factors did not change the results in either of the two groups.

CONCLUSION

Using a low magnesium dialysate bath in hemodynamically stable hemodialysis patients without preexisting advanced cardiac disease does not significantly impact QTcd.

Changes in the QT intervals, QT dispersion, and amplitude of T waves after hemodialysis

BACKGROUND

Increased QT dispersion (QTd) has been associated with an increased risk for ventricular arrhythmias and sudden death in the general population and in various clinical states.

METHODS

We investigated the impact of hemodialysis (HD) on QT, QTd, and T-wave amplitude in subjects with end-stage renal failure. Data on 49 patients on chronic HD were studied. The QT, QTd, and the sum of amplitude of T waves (SigmaT) in millimetre in the 12 ECG leads, along with a host of other ECG parameters, body weight, blood pressure, heart rate, electrolytes, and hemoglobin/hematocrit were measured before and immediately after HD.

RESULTS

QT decreased (380.9 +/- 38.4-363.5 +/- 36.8 ms, P = 0.001), the QTc did not change (406.2 +/- 30.8-405.4 +/- 32.2 ms, P = 0.8), the QTd increased (31.3 +/- 14.6-43.9 +/- 18.6 ms, P = 0.003), and the SigmaT decreased (32.3 +/- 15.7-25.9 +/- 12.6 mm, P = 0.0001) after HD. There was no correlation between the change in QTd and the changes in serum cations, heart rate, the subjects' weight, T-wave duration, and SigmaT. However, the change in QTc correlated inversely with the change in serum Ca(++) (r =-0.339, P = 0.021).

CONCLUSION

QTd increased, the SigmaT decreased, and the QTc and T-wave duration remained stable, after HD. The QTd increase, although may be real, could also reflect measurement errors stemming from the decrease in the amplitude of T waves (as shown recently), imparted by HD; this requires clarification, to use QTd in patient on HD.

The Acute Cardiac Effects of Dialysis

It is well recognized that the procedure of hemodialysis is associated with significant changes in blood pressure and systemic hemodynamics; 20-30% of treatments are complicated by intradialytic hypotension (IDH). There are now an increasing number of studies using electrocardiographic, isotopic and echocardiographic techniques that show that subclinical myocardial ischemia occurs during dialysis. This concept is supported by some studies showing that dialysis can induce acute rises in troponins and creatinine kinase MB, although this has not been found by all authors. Some of this controversy may at least in part be due to the collection of blood samples immediately postdialysis, which is likely to be too early to reliably detect dialysis-induced elevations of cardiac enzymes. Cardiovascular death is the biggest single cause of mortality in dialysis patients and of this sudden death comprises the largest proportion. As such, there is a large body of evidence examining whether dialysis is pro-arrhythmogenic. It is clear that dialysis can increase QTc interval and QT dispersion and is capable of inducing arrhythmias on Holter monitoring, likely due to the interaction of multiple factors, some of which prime for the development of arrhythmias (particularly the presence of preexisting cardiac disease), and some of which act as triggers. However, the link between these electrocardiographic alterations and sudden death is relatively poorly studied. This review summarizes the available literature regarding the acute cardiac effects of dialysis in relation to the above, and discusses how these acute changes may contribute to the genesis of uremic cardiomyopathy and longer term cardiac outcomes.

QT interval dispersion in dialysis patients

The leading cause of mortality in dialysis patients is cardiovascular complications, including ventricular arrhythmias and sudden cardiac death. A reliable non-invasive predictive test of sudden death is therefore important. The interlead variation in duration of the QT interval on the surface electrocardiogram corrected with heart rate (QTc dispersion) might serve as a surrogate for ventricular arrhythmia. Prolonged QTc dispersion is commonly encountered in dialysis patients and possesses an increased risk of all mortality, including cardiovascular mortality. QT dispersion might be affected by shifts of the intracellular electrolytes during dialysis and increasing deposition of iron in cardiac muscles in these patients who have underlying heart diseases. Although no well-designed study has been done, the factors contributing to prolongation of QTc dispersion should be avoided. We summarize the results of the currently available clinical studies that examined QTc dispersion in dialysis patients.

QTc interval in patients with changing edematous states: implications on interpreting repeat QTc interval measurements in patients with anasarca of varying etiology and those undergoing hemodialysis

Associations have been described among weight, amplitude of QRS complexes, and QRS duration (QRSd) in patients with anasarca (AN), and changes in the amplitude of the QRS complexes, QRSd, and QTc after hemodialysis (HD) and in patients with heart failure with associated peripheral edema congestive heart failure. The objective of this study was to evaluate the hypothesis that changes in QTc in patients with AN and after HD are at least partially apparent, due to changing edematous states, and not totally due to altered electrophysiology. QTc was measured in patients with AN on admission, at peak weight (N = 28), and at their subsequent lowest weight (N = 12), in 28 control patients without change in weight during hospitalization, and in one patient before and after 26 HD sessions. In the patients with AN, the QTc was 451 +/- 36 ms on admission and dropped to 423 +/- 46 ms at peak weight (P = 0.005). QTc was 421 +/- 44 ms at peak weight and raised to 434 +/- 30 at subsequent lowest weight (P = 0.32). In the controls, QTc on admission and at discharge were 435 +/- 34 and 428 +/- 23 ms, correspondingly (P = 0.18). QTc increased from 472 +/- 18 ms before to 489 +/- 36 ms after HD (P = 0.017). Alterations in QTc in AN, or HD suggest that the changes in the QTc may be partially only apparent, and due to the electrocardiogram machine-based measurement of the attenuated/augmented QRST complexes resulting from fluid shifts.

Impact of haemodialysis on QTc dispersion in children

BACKGROUND

The purpose of the present paper was to investigate the corrected QT (QTc) interval and QTc dispersion value, and the impact of haemodialysis on these parameters in children with chronic renal failure.

METHODS

Nineteen patients with chronic renal failure receiving haemodialysis were included in the present study. Electrocardiography (ECG), echocardiography and serum biochemistry were performed in all patients. Serum electrolyte levels were measured before and after haemodialysis, at the time of the ECG. Nineteen healthy age- and sex-matched children served as the control group.

RESULTS

Patients with chronic renal failure had greater QTc interval and QTc dispersion compared to control subjects. The patients' sex, age and presence of hypertension or left ventricular hypertrophy (LVH) were not related to QTc interval/dispersion. However, the patients with left ventricular (LV) systolic dysfunction had significantly greater QTc dispersion value. After haemodialysis session, both QTc interval and QTc dispersion values significantly increased. Serum potassium levels significantly decreased, whereas the calcium level significantly increased after the haemodialysis session. The changes in electrolyte values were not associated with the changes in both QTc interval and QTc dispersion.

CONCLUSION

Children receiving haemodialysis may be at greater risk of ventricular arrhythmia and sudden death because QTc dispersion reflects heterogeneous recovery of ventricular excitability.

Cell-associated magnesium and QT dispersion in hemodialysis patients

BACKGROUND

Impaired magnesium (Mg) homeostasis has been implicated in a variety of cardiovascular disturbances, including ventricular arrhythmias and changes in the interval between the onset of wave Q to the end of wave T (QT interval) on electrocardiogram. Cardiac arrhythmias are common in patients on hemodialysis therapy.

METHODS

We investigated the relationship between QT interval corrected for heart rate (QTc) dispersion and Mg content in peripheral blood mononuclear cells (PBMC) of chronic hemodialysis patients treated with high-dose calcium carbonate providing Mg in excess (group I; n = 18) or low-dose calcium carbonate and smaller Mg load (group II; n = 13).

RESULTS

Mean Mg content in PBMC of group I patients (27.9 +/- 4.2 [SD] micromol/L/mg protein) was significantly greater than in group II patients (10.4 +/- 4.1 micromol/L/mg protein; P < 0.05) and greater in both groups than in healthy control subjects (2.75 +/- 0.6 micromol/L/mg protein; P < 0.05). Mean QTc dispersion was significantly longer (74.6 +/- 21.4 milliseconds) in group I than group II (37.8 +/- 13.1 milliseconds; P < 0.02) and longer in both groups than in controls (27.3 +/- 9.6 milliseconds; P < 0.05). After dialysis, in both groups of patients, cell-associated Mg (c-a Mg) levels and QTc dispersion were significantly greater (P < 0.05) than before dialysis started. One week after stopping calcium carbonate treatment, group 1 patients showed significant reductions in predialytic c-a Mg levels (to 19.5 +/- 9.8 micromol/L/mg protein; P < 0.05) and QTc dispersions (to 48.9 +/- 23.7 milliseconds; P < 0.05). Plasma Mg and other electrolyte concentrations prior to and during hemodialysis did not correlate with QTc dispersion.

CONCLUSION

Prolongation of QTc dispersion in patients on chronic hemodialysis therapy could be, at least in part, a consequence of increased concentrations of c-a Mg resulting from excess daily Mg intake.