Cardiac arrhythmias and electrolyte changes during haemodialysis

Deep Learning Using Electrocardiograms in Patients on Maintenance Dialysis

Cardiovascular morbidity and mortality occur with an extraordinarily high incidence in the hemodialysis-dependent end-stage kidney disease population. There is a clear need to improve identification of those individuals at the highest risk of cardiovascular complications in order to better target them for preventative therapies. Twelve-lead electrocardiograms are ubiquitous and use inexpensive technology that can be administered with minimal inconvenience to patients and at a minimal burden to care providers. The embedded waveforms encode significant information on the cardiovascular structure and function that might be unlocked and used to identify at-risk individuals with the use of artificial intelligence techniques like deep learning. In this review, we discuss the experience with deep learning-based analysis of electrocardiograms to identify cardiovascular abnormalities or risk and the potential to extend this to the setting of dialysis-dependent end-stage kidney disease.

Qt Dispersion and Signal-Averaged Electrocardiogram in Hemodialysis and Capd Patients

Objective

The aim of this study was to compare QT dispersion (QTd) and signal-averaged electrocardiogram (SA-ECG) parameters that may predict risk of malignant arrhythmias in patients on hemodialysis (HD), on continuous ambulatory peritoneal dialysis (CAPD), and in controls.

Setting

Controlled cross-sectional study in a tertiary- care setting.

Patients

28 HD (M/F 18/10; mean age 32 ± 9 years), 29 CAPD (M/F 17/12; mean age 34 ± 10 years), and 29 healthy controls (M/F 17/12; mean age 32 ± 8 years) were included.

Interventions

On ECG, minimum (QTmin) and maximum (QTmax) QT duration and their difference (QTd) were measured. In SA-ECG, duration of filtered QRS, HFLA signals less than 40 μV, and RMS voltage (40 ms) were also measured.

Results

Higher serum Ca2+ and lower K+ levels were found in CAPD compared to HD. All QT parameters were increased in HD and CAPD compared to controls. QT dispersion was significantly prolonged in HD compared to CAPD. In HD, QTd was correlated with left ventricular (LV) mass index ( r = 0.53, p = 0.004), but not in CAPD ( r = -0.09, p = 0.63). QT dispersion was significantly prolonged in patients with LV hypertrophy compared to patients without hypertrophy on HD (68 ± 18 ms vs 49 ± 18 ms, p = 0.008). In the analysis of SA-ECG, 3 of the 28 (11%) HD and 2 of the 29 (7%) CAPD patients had abnormal late potentials. Patients on HD and CAPD had significantly higher filtered-QRS duration compared to controls (105 ± 15 ms and 104 ± 12 ms vs 95 ± 5 ms, respectively, p = 0.04). Patients with LV hypertrophy had higher filtered-QRS duration compared to patients without hypertrophy (109 ± 12 ms vs 95 ± 8 ms, p < 0.001).

Conclusion

Dialysis patients had prolonged QTd and increased filtered-QRS duration in SA-ECG compared to controls. Patients on HD had longer QTd than patients on CAPD. QTd has been correlated to LV mass index in HD, but not in CAPD. This difference might be due to the effect of different dialysis modalities on electrolytes, especially the higher serum Ca2+ levels.

Prognosis of Patients with Cirrhosis and AKI Who Initiate RRT

BACKGROUND AND OBJECTIVES

Literature on the prognosis of patients with cirrhosis who require RRT for AKI is sparse and is confounded by liver transplant eligibility. An update on outcomes in the nonlisted subgroup is needed. Our objective was to compare outcomes in this group between those diagnosed with hepatorenal syndrome and acute tubular necrosis, stratifying by liver transplant listing status.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Retrospective cohort study of patients with cirrhosis acutely initiated on hemodialysis or continuous RRT at five hospitals, including one liver transplant center. Multivariable regression and survival analysis were performed.

RESULTS

Four hundred seventy-two subjects were analyzed (341 not listed and 131 listed for liver transplant). Among nonlisted subjects, 15% (51 of 341) were alive at 6 months after initiating RRT. Median survival was 21 (interquartile range [IQR], 8, 70) days for those diagnosed with hepatorenal syndrome and 12 (IQR, 3, 43) days for those diagnosed with acute tubular necrosis (P=0.25). Among listed subjects, 48% (63 of 131) received a liver transplant. Median transplant-free survival was 15 (IQR, 5, 37) days for those diagnosed with hepatorenal syndrome and 14 (IQR, 4, 31) days for those diagnosed with acute tubular necrosis (P=0.60). When stratified by transplant listing, with adjusted Cox models we did not detect a difference in the risk of death between hepatorenal syndrome and acute tubular necrosis (hazard ratio [HR], 0.81; 95% confidence interval [95% CI], 0.59 to 1.11, among those not listed; HR, 0.73; 95% CI, 0.44 to 1.19, among those listed).

CONCLUSIONS

Cause of AKI was not significantly associated with mortality in patients with cirrhosis who required RRT. Among those not listed for liver transplant, mortality rates were extremely high in patients both with hepatorenal syndrome and acute tubular necrosis.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2017_11_09_CJASNPodcast_18_1_A.mp3.

Correlation of corrected QT dispersion with the severity of coronary artery disease detected by SYNTAX score in non-diabetic patients with STEMI

Introduction

Determination of the QT interval dispersion by means of a standard ECG at rest has been widely used for cardiovascular risk assessment during the last 15 years as one of the recent explanations for the development of life threatening ventricular arrhythmias. However, little is known about the relation between QT dispersion and the severity of coronary artery atherosclerosis as defined by SYNTAX score.

Aim of work

The present study was done to assess the correlation between QTc dispersion and the severity of coronary artery disease in acute ST elevation myocardial infarction (STEMI) detected by SYNTAX score.

Patients and methods

It included 50 patients who were non-diabetic, non-hypertensive and diagnosed as acute STEMI within 6 months undergoing coronary angiography in the cath. lab. of Assiut University Hospital. QT dispersion was calculated as the difference between the longest (QT max) and the shortest QT (QTmin) interval recorded by standard 12 lead ECG. The QT interval was corrected by using Bazett's formula (QTc = QT/square root of R-R interval in seconds). Corrected QT dispersion (QTcd) was defined as the difference between the maximum and minimum QTc for a given heart rate. The SYNTAX score is calculated by syntax calculator, a new tool to grade the complexity of coronary artery disease.

Results

Out of 50 participating patients, there were 43 (86%) males with mean age 53.9 ± 12.1 years. The mean QTc dispersion was 83.1 ± 20.3 ms, while mean SYNTAX score was 11.6 ± 6.1. There is a strong positive correlation between QTc dispersion and SYNTAX score. This was not related to age, gender, risk factors or family history of ischemic heart disease. Of note, there was a relationship between QTc dispersion and serum creatinine.

Conclusions

Our study concluded that there is a significant positive correlation between corrected QT dispersion and severity of coronary artery disease as assessed by SYNTAX score.

The effects of different electrolyte composition in dialysate on QTc interval; a controlled trial

INTRODUCTION

Hemodialysis (HD) has impact on the cardiovascular system by inducing changes in the characteristics of body fluids such as PH, temperature and electrolyte concentrations. In the previous studies, prolongation of the QT interval and increase of QT dispersion have been reported during HD sessions. These changes were more significant while using solutions with less potassium and higher bicarbonate during dialysis.

OBJECTIVES

The aim of our study was to investigate the effects of different potassium and bicarbonate concentrations on electrocardiography (ECG) parameters and the electrochemical balance of cell membranes.

PATIENTS AND METHODS

This is a double blind controlled clinical trial with crossover design. This interventional study has been conducted on 36 patients over 18 years who undergoing HD 3 times a week for at least 6 months. Twelve-lead ECG has been obtained before starting and one hour after end of each HD session. The QTc was measured and changes recorded by a cardiologist. Correlations were evaluated by univariate regression analysis.

RESULTS

54.38 years (16 to 77 years), 66.7% were male. No significant increase in QT interval has been seen while dialyzing with 2 meq/l potassium and 24 meq/l bicarbonate, 2 meq/l potassium and 28 meq/l bicarbonate and 3 meq/l potassium and 24 meq/l bicarbonate beside high calcium (2.5 meq/l) dialysate was conducted. Age, gender, serum calcium and serum bicarbonate level before HD session did not influence the mean QT intervals before and after dialysis.

CONCLUSION

Concentration of potassium beside moderate dose of bicarbonate in dialysis bath had not any significant influence on QT intervals after dialysis.

Potassium kinetics during hemodialysis

Hyperkalemia in hemodialysis patients is associated with high mortality, but prescription of low dialysate potassium concentrations to decrease serum potassium levels is associated with a high incidence of sudden cardiac arrest or sudden death. Improved clinical outcomes for these patients may be possible if rapid and substantial intradialysis decreases in serum potassium concentration can be avoided while maintaining adequate potassium removal. Data from kinetic modeling sessions during the HEMO Study of the dependence of serum potassium concentration on time during hemodialysis treatments and 30 minutes postdialysis were evaluated using a pseudo one-compartment model. Kinetic estimates of potassium mobilization clearance (K(M)) and predialysis central distribution volume (V(pre)) were determined in 551 hemodialysis patients. The studied patients were 58.8 ± 14.4 years of age with predialysis body weight of 72.1 ± 15.1 kg; 306 (55.4%) of the patients were female and 337 (61.2%) were black. K(M) and V(pre) for all patients were non-normally distributed with values of 158 (111, 235) (median [interquartile range]) mL/min and 15.6 (11.4, 22.8) L, respectively. K(M) was independent of dialysate potassium concentration (P > 0.2), but V(pre) was lower at higher dialysate potassium concentration (R = -0.188, P < 0.001). For patients with dialysate potassium concentration between 1.6 and 2.5 mEq/L (N = 437), multiple linear regression of K(M) and V(pre) demonstrated positive association with predialysis body weight and negative association with predialysis serum potassium concentration. Potassium kinetics during hemodialysis can be described using a pseudo one-compartment model.

Hemodialysis-induced regional left ventricular systolic dysfunction: prevalence, patient and dialysis treatment-related factors, and prognostic significance

BACKGROUND AND OBJECTIVES

The hemodialysis procedure may acutely induce regional left ventricular systolic dysfunction. This study evaluated the prevalence, time course, and associated patient- and dialysis-related factors of this entity and its association with outcome.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Hemodialysis patients (105) on a three times per week dialysis schedule were studied between March of 2009 and March of 2010. Echocardiography was performed before dialysis, at 60 and 180 minutes intradialysis, and at 30 minutes postdialysis. Hemodialysis-induced regional left ventricular systolic dysfunction was defined as an increase in wall motion score in more than or equal to two segments.

RESULTS

Hemodialysis-induced regional left ventricular systolic dysfunction occurred in 29 (27%) patients; 17 patients developed regional left ventricular systolic dysfunction 60 minutes after onset of dialysis. Patients with hemodialysis-induced left ventricular systolic dysfunction were more often male, had higher left ventricular mass index, and had worse predialysis left ventricular systolic function (left ventricular ejection fraction). The course of blood volume, BP, heart rate, electrolytes, and acid-base parameters during dialysis did not differ significantly between the two groups. Patients with hemodialysis-induced regional left ventricular systolic dysfunction had a significantly higher mortality after correction for age, sex, dialysis vintage, diabetes, cardiovascular history, ultrafiltration volume, left ventricular mass index, and predialysis wall motion score index.

CONCLUSIONS

Hemodialysis induces regional wall motion abnormalities in a significant proportion of patients, and these changes are independently associated with increased mortality. Hemodialysis-induced regional left ventricular systolic dysfunction occurs early during hemodialysis and is not related to changes in blood volume, electrolytes, and acid-base parameters.

Outcomes after the long interdialytic break: implications for the dialytic prescription

A thrice-weekly schedule dominates hemodialysis practice today. Inherent in such a schedule is a 72-hour interweek break over the weekend. A growing body of evidence suggests that this break may be associated with increased cardiovascular morbidity and mortality. Five recent studies have linked dialysis session timing to higher cardiovascular event rates, and have shed light on possible underlying physiologic mechanisms. We reviewed outcome data linking the "long break" to cardiovascular outcomes, and suggest physiologic rationale for this relationship while identifying knowledge gaps that require further study to inform discussions regarding the application and composition of individualized dialysis prescriptions. Further work is needed to determine the relative importance of electrolyte perturbations and hemodynamic shifts in the relationship between the long break and cardiovascular mortality. The evidence suggests that at least in some at-risk patients, an individualized approach to the dialytic schedule and prescription is warranted.

QT Interval and QT Dispersion in Patients Undergoing Hemodialysis: Revisiting the Old Theory

AIMS

We sought to explore the response of the corrected QT (QTc) interval duration and QT dispersion (QTD) to hemodialysis.

METHODS

We enrolled 50 patients with end-stage renal disease undergoing regular hemodialysis. Blood samples were drawn for measurement of serum electrolytes, and a 12-lead ECG was performed to measure the QTc interval duration and QTD, immediately before and just after dialysis sessions.

RESULTS

The mean age of the cohort was 42.8 ± 12.2 years (58% males). Both the QTc duration and QTD showed marked variability after hemodialysis. A significant correlation was found between the decrease of both serum potassium and magnesium levels after dialysis and the post-dialysis QTc interval duration, with Pearson's correlation coefficients r = -0.43 and r = -0.34, p = 0.002 and p = 0.01, respectively. Patients with a post-dialysis increase of QTc interval duration had a significantly higher percentage of reduction of serum potassium (p = 0.029), whereas patients with a post-dialysis increase of QTD had a significantly higher percentage of reduction of serum magnesium (p = 0.03).

CONCLUSION

Our findings suggest a highly variable response of the QTc interval duration and QTD to hemodialysis. The post-dialysis QTc interval duration inversely correlated with the decrease of both serum potassium and magnesium levels after dialysis.

Incremental prevalence of fractionated and inhomogeneous propagation of sinus impulses with increasing atrial depolarization abnormality among outpatients

INTRODUCTION

Prolonged P-wave duration (P-dur) and excessive P-wave dispersion (P-disp) are purported arrhythmogenic substrates for atrial fibrillation. However, the extent of involvement of inhomogeneous, sinus impulse propagation demonstrated by excessive P-disp (> 40 ms) has not been evaluated in relation to increasing P-dur.

METHODS

We appraised our previously studied sample of 500 consecutively numbered, otherwise unselected, electrocardiograms (ECGs) of outpatients from the University of Massachusetts, Worcester, Massachusetts for P-disp, P-dur and P-wave axis (P-axis). P-disp, defined as the difference of the duration between the widest and narrowest P wave, and the greatest P-dur after a 12-lead ECG search, was measured manually to the nearest 10 ms. Normal P-axis was considered 0 to + 75 degrees by manually constructing the mean frontal plane electrical P-axis from the limb leads.

RESULTS

After excluding those with atrial arrhythmias, paced rhythms, errors in lead placement, P waves with low amplitude or overall technically poor tracing, 428 ECGs depicting sinus rhythm formed our final sample. P-dur was strongly associated with P-disp (p<0.0001) but the correlation remained weak (r=0.42). However, when P-dur was divided into 10 ms increments, the prevalence of abnormal P-disp rose incrementally with P-dur, with or without consideration of the P-axis. The prevalence of abnormal P-disp doubled from 30% in those with P-dur of 100 ms to > 60% in those with P-dur of 120 ms. Further, the prevalence exceeded 80% with P-dur of 130 ms and reached 100% with P-dur > 160 ms.

CONCLUSION

With increasingly prolonged atrial depolarization, the associated inhomogeneity of sinus impulse propagation across the atria increases. P-dur and P-disp are associated with each other and are consistent with abnormal atrial conduction properties.

Effect of acetate-free biofiltration with a potassium-profiled dialysate on the control of cardiac arrhythmias in patients at risk: a pilot study

Cardiac arrhythmias are a frequent event in chronic hemodialysis patients. The aim of this study was to evaluate the efficacy and safety of acetate-free hemofiltration with potassium-profiled dialysate (AFB-K) dialysis compared with constant potassium acetate-free biofiltration (AFB). Twelve patients (mean age 79 years) affected by cardiac arrhythmias or at a high risk for arrhythmia (advanced age, hypertension, left ventricular hypertrophy, heart valve disease, coronary artery disease, diabetes, paroxysmal atrial fibrillation) participated in a single-center, sequential cohort study. All were treated with hemodialysis 3 times per week, using constant potassium AFB for the first 3 weeks, followed by an AFB-K dialysate for the subsequent 3 weeks. The hemofilter, duration of dialysis, and electrolyte concentration were the same in both treatments. Both AFB-K and constant potassium AFB dialytic techniques were safe and well tolerated. The results of biochemical tests were similar, except for serum potassium levels after 2 hr of dialysis, which were significantly higher in the AFB-K group (4.0 mmol/L) than in the constant potassium AFB group (3.6 mmol/L) (p<0.001). All cardiac variables improved during AFB-K dialysis. There was a significant reduction of postdialysis QT intervals corrected for heart rate in the AFB-K group (448.8 ms) compared with the constant potassium AFB group (456.8 ms) (p=0.039). The severity and mean number of ventricular extasystoles also decreased (163.5 vs. 444.5/24 hr). Potassium profiling during hemodialysis treatment may be beneficial for patients with arrhythmias or at those risk of arrhythmias, particularly those with predialysis hyperkalemia.

Experimental therapies in renal replacement: the effect of two different potassium acetate-free biofiltration protocols on striated muscle fibers

Dramatic removal of potassium during hemodialysis sessions can induce changes in the electrical properties of nerve cells or muscle fibers, which may underlie neuromuscular symptoms referred by end-stage renal disease patients. The primary aim of our study was to investigate the effects of acetate-free biofiltration (AFB) on the amplitude of compound motor action potential (cMAP) obtained after stimulation of the ulnar nerve at the wrist. The secondary aim was to compare the effect of two different potassium removal modalities on cMAP amplitude and to analyze the effects on muscular force by specific dynamometric tests. Twenty-eight patients received dialysis for 4 h, 3 times per week, first with standard AFB with constant potassium (AFB) and then with AFB with a variable concentration of potassium in the dialysis bath (AFB(K)). The amplitude of cMAP was determined after ulnar nerve stimulation at the wrist at different time intervals: at the start of dialysis; at 15, 45, 90, and 120 min after beginning the session; and at the end of treatment. At the same time intervals, muscle force generation was determined using a dynamometer. Finally, we measured plasma electrolytes, intraerythrocytic potassium, and the electrical membrane potential at rest (REMP) of the erythrocytic membrane. The main finding of this study was a significant reduction of cMAP amplitude in the first 45 min after AFB, which paralleled the reduction in serum potassium levels. Moreover, there was a reduction of muscular strength determined with dynamometric measurements. Potassium removal induced by the two different modalities of AFB may significantly affect myocardial and fibromuscular cells by modulating the electrochemical balance of cell membranes. The transient alteration of the electrical properties on voluntary striated muscle fibers may contribute to the brief reduction in muscular strength we detected in patients who underwent AFB. AFB(K) can minimize the negative effects of standard AFB treatment on neuromuscular excitability, most likely through a more gentle variation of potassium levels during dialysis.

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 cardiovascular implications of hypokalemia

The role of potassium in the progression of cardiovascular disease is complex and controversial. Animal and human data suggest that increases in dietary potassium, decreases in urinary potassium loss, or increases in serum potassium levels through other mechanisms have benefits in several disease states. These include the treatment of hypertension, stroke prevention, arrhythmia prevention, and treatment of congestive heart failure. Recently, the discovery that aldosterone antagonists not only decrease sodium reabsorption and decrease potassium secretion in the nephron, but also decrease pathological injury of such nonepithelial tissues as the myocardium and endothelium, has generated great controversy regarding the actual mechanisms of benefit of these agents. We review the available data and draw conclusions about the relative benefits of modulating potassium balance versus nonrenal effects of aldosterone blockade in patients with cardiovascular disease.

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.

The effect of two different protocols of potassium haemodiafiltration on QT dispersion

BACKGROUND

The risk of developing cardiovascular diseases is higher in patients on haemodialysis than in the general population. These patients may develop arrhythmias that depend on the extra- and intracellular concentrations of potassium. ECG findings, particularly the QT interval and its dispersion (QT(d)) and the QT(c) (QT interval corrected for heart rate according to Bazett's formula) and its dispersion (QT(cd)), may be direct indicators of the risk of developing arrhythmia.

METHODS

Our cohort comprised 28 patients who were dialysed for 3.5-4 h three times per week, first with haemodiafiltration with a constant potassium concentration (HDF) in the dialysis bath then with haemodiafiltration with variable concentrations of potassium (HDF(k)). ECGs were done at different time intervals: at the start of dialysis (T(0)), at 15 (T(15)), 45 (T(45)), 90 (T(90)) and 120 min (T(120)) after the beginning of the session, and at the end of treatment (T(end)). ECG-derived data (QT, QT(d), QT(c) and QT(cd)) were measured. At the same time points, plasma electrolytes, intra-erythrocytic potassium and the electrical membrane potential at rest (REMP) of the erythrocytic membrane were measured.

RESULTS

Plasma potassium concentration diminished more gradually in HDF(k) than in HDF, the difference being statistically significant at T(15) and T(45) (P<0.05), and T(90) (P<0.01). The intra-erythrocytic potassium concentration remained constant throughout the observation period. In both HDF and HDF(k), REMP was lower at all points after T(0) (P<0.05), but the reduction was greater and more significant in HDF than in HDF(k) at T(15) and T(120) (P<0.05). ECG revealed a statistically significant diminution in HDF(k) vs HDF in the measures of dispersion of QT and QT(c) at T(15), T(90), T(120) and T(end) (P<0.01) and of QT(cd) at T(45) (P<0.05). The mean of QT(d), adjusted for plasma potassium, increased over time in HDF with large alternate mean increase and decrease peaks and error intervals. In HDF(k), instead, there was a progressive and constant diminution with minor error intervals. QT(cd) adjusted for plasma potassium had the same trend. A marked difference was found between the final values in standard HDF and those in HDF(k).

CONCLUSIONS

HDF and HDF(k) have significantly different effects on QT(c). ECG data demonstrate that the risk of arrhythmia could be lower, with a variable removal of potassium during haemodialysis. With HDF but not HDF(k), hyperpolarization of the cell membrane is detected, and this could have a destabilizing effect on different types of cardiac cell, giving rise to retrograde circuits.

Effect of premature ventricular beats on manual and automatic repolarization measurements

OBJECTIVE

To compare QT interval and QT dispersion in ventricular ectopic beats with measurements from the preceding and the immediately following sinus beats, and investigate differences between manual and automatic measurements.

PATIENTS

Eleven chronic uremic patients.

MAIN OUTCOME MEASURES

ECGs were recorded during hemodialysis treatment and 12-lead sections containing five consecutive beats were extracted, each containing four sinus beats and one centrally-positioned premature ventricular beat. QT measurements were performed both manually and with a computer-automated technique.

RESULTS

T wave amplitude was greater in the ectopic beats compared to the sinus beats (0.61 +/- 0.18 vs. 0.23 +/- 0.06 mV, P <.001). The ectopic beats had a greater QT than the sinus beats when measured manually (415 +/- 35 ms vs. 386 +/- 28 ms, P <.001), or automatically (375 +/- 30 vs. 366 +/- 27 ms, P<.01). The sinus beats following the ectopics had a greater QT than the preceding sinus beats (400 +/- 27 vs. 386 +/- 28 ms, P<.001, manual; 382 +/- 24 vs. 366 +/- 27 ms, P<.001, automatic). Differences in QT dispersion were seen only between the ectopic and sinus beats (91 +/- 31 vs. 58 +/- 27 ms, P <.001, manual; 68 +/- 33 vs. 49 +/- 35 ms, P <.001, automatic).

CONCLUSIONS

Manual measurement resulted in greater QT values than automatic measurement. Both techniques identified differences between sinus and ectopic beats. The ventricular ectopic beats resulted in an increase in the QT of the immediately following sinus beats. These results confirm the need to interpret QT measurements with care in the presence of ectopic beats.

Serum Potassium Handling at Pre- and Posthemodialysis in Patients with End-Stage Renal Disease

The current study simultaneously measured serum and red blood cell (RBC) K+ as well as plasma pH, bicarbonate, serum insulin, and aldosterone at pre-, end-, and at 5, 11, and 19 hours posthemodialysis in 25 patients with end-stage renal disease and evaluated the factors influencing serum K+ levels during those periods. Our patients were studied under their current dietary conditions. At end-dialysis, serum K+ levels decreased, but RBC K+ levels were not changed. At this time point, the decrease in serum K+ levels was exclusively caused by removal of K+ by dialysis. At 5 hours postdialysis, serum K+ rapidly increased, whereas RBC K+ decreased. The 5 hour postdialysis serum K+ increase negatively correlated with the decrease in serum insulin levels. At 11 hours postdialysis, serum K+ slowly but significantly increased, and RBC K+ increased to those levels at pre- and end-dialysis. At 19 hours postdialysis, serum K+ further increased, but RBC K+ remained stable. From 5 to 19 hours postdialysis, the increase in serum K+ was independent of changes in plasma pH, bicarbonate, insulin, and aldosterone but was associated with both the predialysis serum K+ levels and the magnitude of the decrease in serum K+ at end-dialysis.

Changes in the corrected QT interval and corrected QT dispersion during haemodialysis

The link between increased QT dispersion and cardiac death in subjects with diabetes and arterial disease is well recognised. Corrected QT dispersion was studied in subjects with end stage renal failure on haemodialysis. Thirty one stable, chronic subjects on haemodialysis had 12-lead electrocardiograms (ECGs) taken before and after a single haemodialysis session. The QT interval was measured manually in each and the corrected QT and corrected QT dispersion calculated. Serum concentrations of potassium, calcium, and magnesium were measured at the same time as ECG acquisition. Corrected QT dispersion increased from a mean (SEM) 90.6 (5.8) to 117.7 (10.2) ms (p=0.002). Serum potassium and magnesium decreased from 5.0 (0.14) to 3.5 (0.09) mmol/l and 0.95 (0.04) to 0.89 (0.09) mmol/l respectively, while serum calcium increased from 2.56 (0.04) to 2.77 (0.04) mmol/l. Intradialytic weight fell by a mean of 2.1 kg. There was no significant correlation between the change in QTc dispersion and the changes in measured serum anions or the subjects' weight during dialysis. Corrected QT dispersion was higher in subjects on haemodialysis than previously suggested normal values, and was significantly increased by haemodialysis. This reflects increased inhomogeneous ventricular repolarisation, which may lead to an increased risk of arrhythmias and sudden death. Studies looking at QT dispersion in subjects on dialysis should standardise the timing of ECG recordings taken with respect to dialysis.

Hyperkalemia in dialysis patients

Serious hyperkalemia is common in patients with end-stage renal disease (ESRD) and accounts for considerable morbidity and death. Mechanisms of extrarenal disposal of potassium (gastrointestinal excretion and cellular uptake) play a crucial role in the defense against hyperkalemia in this population. In this article we review extrarenal potassium homeostasis and its alteration in patients with ESRD. We pay particular attention to the factors that influence the movement of potassium across cell membranes. With that background we discuss the emergency treatment of hyperkalemia in patients with ESRD. We conclude with a review of strategies to reduce the risk of hyperkalemia in this population of patients.

Cardiopulmonary events during hemodialysis: effects of dialysis membranes and dialysate buffers

Adverse cardiac and pulmonary events are frequently observed during hemodialysis and contribute to significant morbidity and mortality. The temporal relationship between these events during the intradialytic period has not been well defined. To examine the event rate and timing of silent ischemia, cardiac ectopy, and hypoxemia, we conducted a prospective, single-blind, randomized study of 10 subjects undergoing maintenance hemodialysis with four contiguous combinations of dialysis membranes (cuprammonium or polysulfone) and dialysates (acetate or bicarbonate). The frequency of oxygen desaturation events peaked during the first 2 hours, whereas silent myocardial ischemia and supraventricular ectopies occurred more often in the later hours. Ventricular ectopy occurred steadily throughout the intradialytic period. The combination of acetate dialysis and cuprammonium membrane is associated with the most frequent events. We conclude that cardiopulmonary events can occur frequently during hemodialysis, and the frequency is dependent on the type of dialysis membrane and dialysate buffer used.

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

Chronic renal failure patients on maintenance hemodialysis (HD) have a number of ECG abnormalities and cardiac arrhythmias. Clinical and experimental data have shown that increased QT dispersion is associated with severe ventricular arrhythmias and sudden cardiac death. Therefore, the aim of this study was to investigate whether the uremic patients receiving long-term HD have increased QTc interval and/or QTc dispersion compared to normal subjects and to evaluate the effect of electrolyte changes between the predialysis and postdialysis phases on these parameters. Forty patients with end-stage renal failure on long-term HD (22 men, 18 women, mean age 44 years) were included in this study. Serum concentrations of K+, Na+, Ca++, Mg++, Cl-, phosphate, urea, creatinine, HCO3-, and arterial blood gases (PO2, PCO2), together with blood pH, were monitored and QTc intervals and QTc dispersion were measured from 12-lead ECG in predialysis and postdialysis phases. The hemodialyzed patients had an increased predialysis QTc maximum interval and QTc dispersion compared to normal subjects (480 +/- 51 vs 310 +/- 38 msec, p < 0.001 and 61 +/- 17 vs 42 +/- 14 msec, p < 0.001, respectively). Both QTc maximum interval and QTc dispersion increased significantly at the end of the HD (480 +/- 51 vs 505 +/- 49 msec p < 0.001 and 61 +/- 17 vs 86 +/- 18 msec, p < 0.001, respectively). The serum K+ (5.3 +/- 0.56 vs 3.36 +/- 0.41 mEq/L, p < 0.001), phosphate (7.19 +/- 1.62 vs 3.81 +/- 1.02 mg/dL, p < 0.001), magnesium (0.87 +/- 18 vs 0.75 +/- 0.14 mg/dL) and urea concentrations (174 +/- 22 vs 74 +/- 14 mg/dL, p < 0.001) significantly decreased, whereas the Ca++ (2.21 +/- 0.18 vs 2.47 +/- 0.24 mg/dL, p < 0.001), HCO3- (15.5 +/- 3.2 vs 20.1 +/- 3.4 mmol/L, p<0.001) concentrations and pH (7.27 +/- 1.1 vs 7.43 +/- 1.2, p < 0.001) significantly increased after HD compared to predialysis values. There was significant correlation between the QT dispersion increase and serum electrolyte changes (K+, Ca++, and pH levels) (p < 0.05). The association between serum electrolyte changes, acid-base status and QT measurements might provide new insights into the evaluation of the ionic bases involved in inhomogeneous ventricular repolarization.

QTc dispersion increases during hemodialysis with low-calcium dialysate

BACKGROUND

The risk of ventricular arrhythmias is known to increase during hemodialysis (HD) treatment, but the cause of this phenomenon has remained unidentified. QT dispersion (= QTmax - QTmin) reflects heterogeneity of cardiac repolarization, and increased dispersion is known to predispose the heart to ventricular arrhythmias and sudden cardiac death.

METHODS

We studied the effect of dialysate calcium concentration on cardiac electrical stability during HD treatment in 23 end-stage renal disease patients. Three HD treatments were applied with dialysate Ca++ concentrations of 1.25 mmol/L (dCa++1.25), 1.5 mmol/L (dCa++1.5), and 1.75 mmol/L (dCa++1.75). The QTc interval and QTc dispersion were measured before and after the three sessions.

RESULTS

With the dCa++1.5 and dCa++1.75 dialyses, serum Ca++ increased and the QTc interval remained stable (dCa++1.5) or decreased (dCa++1.75), but no significant change was noted in QTc dispersion. With dCa++1.25 HD, serum Ca++ decreased (1.24 +/- 0.11 vs. 1.20 +/- 0.09 mmol/L, P < 0. 05), and both the QTc interval (403 +/- 27 vs. 419 +/- 33 ms, P < 0. 05) and QTc dispersion increased (38 +/- 19 vs. 49 +/- 18 ms, P < 0. 05). The change in the QTc interval correlated inversely with the change in serum Ca++ (r = -0.68, P < 0.0001). Except for serum Ca++ and plasma intact parathyroid hormone, predialysis and postdialysis values in other blood chemistry, blood pressure, heart rate, body weight, and total ultrafiltration were equal in the three dialysis sessions.

CONCLUSION

This study is the first, to our knowledge, to demonstrate that HD increases QTc dispersion if a low-calcium (dCa++1.25) dialysate is used. This indicates that the use of low-calcium dialysate may predispose HD patients to ventricular arrhythmias and that perhaps it should be avoided, at least when treating patients with pre-existing cardiac disease.

QT dispersion in patients with end-stage renal failure and during hemodialysis

Interlead variability of the QT interval in surface electrocardiogram (ECG), i.e., QT dispersion, reflects regional differences in ventricular recovery time, and it has been linked to the occurrence of malignant arrhythmias in different cardiac diseases. The purpose of the study was to assess the effect of hemodialysis on QT and corrected QT (QTc) interval and dispersion in chronic hemodialyzed patients. Data of 34 nondiabetic patients (male/female = 21/13; mean age, 54 +/- 15 yr) on chronic hemodialysis were studied. Polysulfone capillaries and bicarbonate dialysate containing (in mEq/L) 135 Na+, 2.0 K+, 1.5 Ca2+, and 1.0 Mg2+ were used. Simultaneous 12-lead ECG were recorded before and after hemodialysis in a standard setting. The QT intervals for each lead were measured manually on enlarged (x3) ECG by one observer using calipers. Each QT interval was corrected for patient heart rate: QTc = QT/square root of RR (in milliseconds [ms]). The average cycle intervals were 853 +/- 152 ms predialysis and 830 +/- 173 ms postdialysis; the difference was not significant. The maximal QT interval changed significantly from 449 +/- 43 to 469 +/- 41 ms (P < 0.01). The corrected maximal QT interval increased significantly from 482 +/- 42 to 519 +/- 33 ms (P < 0.01). The QT dispersion changed from 56 +/- 15 to 85 +/- 12 ms (P < 0.001) and the corrected QT interval dispersion from 62 +/- 18 to 95 +/- 17 ms (P < 0.001). During hemodialysis, the serum potassium and phosphate levels decreased from 5.5 +/- 0.8 to 3.9 +/- 0.5 (mM) and from 2.3 +/- 0.5 to 1.6 +/- 0.4 (mM), respectively, whereas calcium increased from 2.2 +/- 0.23 to 2.5 +/- 0.22 (mM). It is concluded that hemodialysis increases the QT and QTc interval and QT and QTc dispersion in patients with end-stage renal failure. Thus, it may be stated that the nonhomogeneity of regional ventricular repolarization increases during hemodialysis. Measurement of QT and QTc dispersion is a simple bedside method that can be used for analyzing ventricular repolarization during hemodialysis.

[Cardiac pathology of extracardiac origin (IX)> Cardiac pathology in the patient with chronic nephropathy]

Cardiac disease constitutes a common complication among patients with renal failure. This is partly due to the high incidence of shared risk factors, such as hypertension or diabetes mellitus, and some to specific factors inherent in renal disease. It implies a high incidence of cardiac failure and ischemic heart disease (frequently without significant coronary artery obstructions) with important associated morbidity and mortality. Pericardial disease, valvular involvement and arrhythmia are also common among these patients. The management of these complications in patients with endstage renal disease has some particularities, specially in the field of drug therapy.

Autonomic neuropathy predisposing to arrhythmias in hemodialysis patients

Arrhythmias are frequent among the dialysis population and can cause symptoms of palpitations or dizziness. Since autonomic disturbances are known to cause an increased arrhythmogenic stimulus, we questioned whether the presence of central autonomic neuropathy increased the frequency of arrhythmias as identified by 24-hour electrocardiographic monitoring in dialysis patients. Seventy-one patients were randomly chosen from patients established on dialysis in two centers. The mean age of the patients was 71.3 years (median age, 67 years) and median duration on dialysis was 17.0 months (range, 1 to 175 months). Four patients had diabetes. Each patient was tested for autonomic control of blood pressure and heart rate, and underwent Holter electrocardiographic monitoring, commencing 30 minutes before dialysis, for a 24-hour period. The tapes were then analyzed for ventricular and atrial rhythm changes. There was a significantly increased incidence of arrhythmias in individuals with abnormal blood pressure responses (P = 0.005), heart rate responses (P = 0.01), and combined blood pressure and heart rate responses (P = 0.004). We conclude that patients with autonomic dysfunction had an increased frequency of arrhythmias during dialysis.

Electrocardiographic abnormalities in patients receiving hemodialysis

We assessed standard 12-lead and Holter electrocardiographic (ECG) abnormalities in maintenance hemodialysis (HD) patients. Of 221 outpatients receiving HD, 143 (65%) had ECG abnormalities. Rates were higher in male, elderly, hypertensive, and diabetic patients than in female, younger, normotensive, and nondiabetic patients. The prevalence of ECG changes correlated inversely with HD duration. Serial ECGs were compared in 87 patients whose average HD duration was 7.5 +/- 2.5 years. Thirty-four patients (39%) showed normal ECGs throughout, 27 (31%) relatively stable abnormalities, 22 (25%) worsening, and 4 (5%) reversion to normal. Age, hypertension, and diabetes are factors related to abnormal ECG findings. Among the 142 Holter recordings from 72 patients, 70 (97%) were basically in sinus rhythm, and 2 (3%) were in atrial fibrillation. The average frequency of supraventricular premature contractions (SVPCs) was 1597 +/- 9725 per 24 hours, and that of ventricular premature contractions (VPCs), 556 +/- 1415. VPCs were multifocal in 9%, in runs in 25%, and early in 1%. In 29 (40%) of recordings, VPCs appeared mainly during and for several hours after HD. ST-T changes were seen in 43 (60%). In 11, ST depression occurred during and a few hours after HD. Patients receiving HD showed diverse ECG abnormalities. Holter ECGs revealed a high incidence of arrhythmias and ST-T changes, which frequently appeared in relation to HD timing.

Hemodialysis using a Constant Potassium Gradient: Rationale of a Multicenter Study

The aim of this study is to evaluate the relationship between two different procedures for potassium removal during hemodialysis (HD) and cardiac arrhythmias. Cell excitability and the transmission of impulses may be influenced by variations of resting membrane potential (RMP). The rapid decrease of plasma potassium during the first two hours of standard HD causes a membrane hyperpolarization. A different K+ kinetic, with a gradual and constant elimination of K+ during HD, may reduce this further unphysiological aspect and its clinical consequences. This can be obtained keeping blood-dialysate K+ gradient as constant as possible with the use of a dialysate K+ concentration (Kd) decreasing during HD. Our experimental studies on various K+ intradialytic gradients seem to indicate as optimal to this purpose K+ gradients of 1.5 mEq/l at the beginning of dialysis, esponentially decreasing during treatment to Kd values of 2.5 mEq/l at the end of dialysis (variable Kd). Patients included in the trial will be submitted to two different methods of treatment with Kd 2 mEq/l and variable Kd, and to a 24 hours ECG the day of dialysis. We will compare the number of intra and interdialytic premature ventricular complexes to evaluate the impact of two different models of potassium removal on arrhythmias.