QT/corrected QT (QTc) intervals and QT/QTc dispersions in children with chronic renal failure

Electrocardiographic measurements in children with pre-dialysis chronic kidney disease and undergoing kidney replacement therapy

Cardiovascular diseases are the main causes of morbidity in children with chronic kidney disease (CKD). Electrocardiography (ECG) can provide important information about cardiac functions and parameters associated with sudden cardiac death. This study aims to evaluate the potentially dangerous changes in CKD and kidney replacement therapies by ECG and to determine the value of ECG in predicting cardiovascular outcome compared with echocardiography. 101 patients with CKD were divided into subgroups according to treatment modalities as pre-dialysis CKD, hemodialysis (HD), peritoneal dialysis (PD) and kidney transplantation (KTx). Differences in anthropometric measurements, laboratory results, blood pressures, ECG monitoring were compared within groups as well as with 40 healthy controls. Available echocardiographic findings were noted. In the patients, HD group had highest frequency of hypertension. ECG revealed prolonged QTc as more frequent (16.8% vs 0%, p = 0.006) and higher QTcD (56.7 ± 6.5 vs 39.9 ± 5.1 ms, p = 0.001) in the patients compared to controls, especially in dialysis patients, whereas lowest values were in KTx subgroup. Left ventricular (LV) hypertrophy (LVH) was more frequent (47.1%) in HD compared to other CKD subgroups in ECG (p = 0.052). Echocardiography also showed LV mass index as highest in HD and lowest in KTx (121.4 ± 55.7 vs 63.7 ± 18.3 g/m2, p = 0.000), with numerically highest LVH in HD (58.3%, p = 0.063).  Conclusion: ECG can be used to detect cardiovascular problems in patients with CKD, especially in HD. As ECG results were in line with echocardiography, patients with ECG abnormalities suggestive of LVH should be referred for echocardiographic assessment. What is Known: • Cardiovascular diseases such as coronary artery disease, congestive heart failure, arrhythmias and sudden cardiac death are major causes of morbidity and mortality in chronic kidney disease. • Electrocardiography has significant advantages in demonstrating cardiac functions in children because it is readily available, non-invasive and often non-experts can interpret the results. What is New: • The heart rate is higher, QTc is longer and QTcD is higher in dialysis patients and the prolonged QTc is more frequent in patients with underlying glomerular diseases. • Left ventricular hypertrophy is more common in HD patients and those with hypertension, hypercalcemia, anemia or glomerular etiology. The cardiovascular risky conditions are less frequent in the patients with kidney transplantation.

Evaluation of T-wave alternans in pediatric patients with chronic renal failure

INTRODUCTION

Microvolt T-wave alternans (TWA) is known to be useful in prediction of ischemia and sudden death in high-risk populations and there are no studies in children with chronic renal failure (CRF). Cardiac problems seem to be responsible for an important part of death in children and young adults with CRF. The aim of this study is to evaluate Holter microvolts TWA measurements in children with CRF comparing to the control group.

METHODS

This prospective study included 40 patients with CRF and 48 healthy controls. The history, echocardiography and microvolt TWA values based on 24-hour ECG recordings of the patients were evaluated. Analysis of microvolt TWA was considered on the basis of three leads (V5, V1 and AVF).

RESULTS

Compared with the controls, the mean systolic and diastolic blood pressure values and average heart rates were significantly higher in the children with CRF (p = 0.001 and p = 0.026, respectively). Also, the values of left ventricular internal dimensions at end diastole and end-diastolic volume were significantly higher in CRF group (p = 0.01 and p = 0.049, respectively) and couplet ventricular extrasystole was detected in 2 patients with CRF. Consequently, all TWA values in three leads were increased in CRF group than the control group but the only increase in V5 lead was statistically significant (p = 0.028).

CONCLUSIONS

This study has demonstrated that microvolt TWA values increased in pediatric patients with CRF. TWA might be used for early risk assessment in pediatric patients with CRF in the future.

Effect of Metabolic Acidosis on QT Intervals in Patients with Chronic Kidney Disease

Background

There is a strong association between chronic kidney disease (CKD) and cardiovascular events. Increased arrhythmia risk in kidney disease is one of the main predominant factors in increased mortality and sudden cardiac death. To estimate this risk, noninvasive measurement of repolarization abnormalities including QT interval and its heart rate-corrected value (QTc) with surface ECG, are commonly used parameters in clinical practice. The aim of this study is to examine the effect of CKD-related problems – mainly acidosis – on QT intervals.

Methods

30 patients with stage 3–5 CKD whose serum bicarbonate concentrations below 20 mmol/L were included in the study. Alkali therapy with oral sodium bicarbonate was used to maintain the serum bicarbonate concentration in the normal range. At the beginning all patients had sinus rhythm on surface ECG records. Kidney function tests including serum urea, serum creatinine, uric acid, blood gas analysis, and electrolytes were analyzed at the beginning and at the end of alkali treatment. All patients underwent 12 lead-ECGs, recorded simultaneously. One cardiologist examined the ECGs manually in terms of QT intervals, corrected for heart rate (QTc), QT dispersion (QTd) and corrected QT dispersion (QTcd).

Results

There were statistically significant differences in QT intervals, QTc, QTd and QTcd before and after sodium bicarbonate treatment. The correlation analyses revealed that there were significant negative correlations in pretreatment ECGs of patients between QTd and QTcd with blood pH level. Multivariate analyses between biochemical parameters and QTd-QTcd intervals have revealed that pH was related to QTd and QTc.

Conclusions

This study demonstrated that QT intervals on surface ECG are decreased after treatment of acidosis in CKD. Further studies are needed to show whether increased QT intervals cause ventricular arrhythmias in CKD.

Prediabetes and blood pressure effects on heart rate variability, QT-interval duration, and left ventricular hypertrophy in overweight-obese adolescents

This ancillary, descriptive correlational study examined the effect of glucose regulation, blood pressure (BP), and their combined effects on cardiac autonomic function in 128 overweight-obese 11-18-year-olds. Measures included body mass index, resting BP, fasting glucose, glucose tolerance, and cardiac autonomic function (heart rate variability, QT, and Cornell voltage). After adjusting for age and gender, multivariate analysis of covariance revealed no differences in cardiac autonomic measures based on glucose regulation (p = .319), BP (p = .286), or the interaction between glucose regulation and BP (p = .132). The additive effect of prediabetes and elevated BP did not impact cardiac autonomic function in overweight-obese youth.

Cardiovascular disease in children with CKD or ESRD

Cardiovascular disease accounts for 40% of all deaths among pediatric patients with end-stage renal disease (ESRD). ESRD has a particularly large influence on the cardiovascular system in children, as indicated by the more than 700-fold increased risk of cardiac death in affected individuals compared with healthy children of the same age. The prevalence of ESRD is low in children, however, and, consequently, few cardiac deaths occur. As a result, prospective follow-up studies of cardiac risk factors in the pediatric setting are lacking. Nevertheless, cross-sectional data on cardiac disease in children with ESRD have started to emerge. Arterial medial calcification is more prominent in children than classic atherosclerotic intimal calcification. Current data suggest that endothelial dysfunction appears early in renal failure in children, and is followed by arterial medial calcification. This calcification causes arterial wall stiffening and subsequently left ventricular hypertrophy. High systolic blood pressure and serum concentrations of intact parathyroid hormone, calcium and phosphate, as well as long-term dialysis, seem to be important risk factors for cardiovascular disease in pediatric patients with ESRD. These features are important targets for preventive intervention. This Review summarizes the currently available data on cardiovascular disease in children with renal failure.

Autonomic nervous system functions in children with breath-holding spells and effects of iron deficiency

AIM

To analyse the activity of the autonomic nervous system during breath-holding spells, we assessed the ECG changes, including ventricular repolarization parameters before and during the spell. We also analysed the effects of iron deficiency on these ECG parameters.

METHODS

The study group consisted of 37 children with breath-holding spells (30 cyanotic, 7 pallid) (mean age+/-SD: 12.9+/-10.8 mo). Twenty-six healthy children (mean age+/-SD: 14.4+/-8.6 mo) served as a control group. All patients and controls had standard 12-lead simultaneous surface ECG. All patients had ECG recordings during at least one severe breath-holding spell obtained by "event recorder". Traces obtained by "event recorder" were analysed in terms of mean heart rate and the frequency and duration of asystole during the spell.

RESULTS

Respiratory sinus arrhythmia on standard ECGs and asystole frequency during spells were higher in patients with pallid breath-holding spells. Patients with iron deficiency had a lower frequency of respiratory sinus arrhythmia and prolonged asystole time during the spell. There was no difference in terms of ventricular repolarization parameters (QT/QTc intervals and QT/QTc dispersions) between patients and controls and between patient subgroups (cyanotic versus pallid).

CONCLUSION

These results confirmed the presence of autonomic dysregulation in children with breath-holding spells. Iron deficiency may have an impact on this autonomic dysregulation. Ventricular repolarization was unaffected in patients with breath-holding spells.

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 spectrum of cardiovascular disease in children with predialysis chronic kidney disease

Cardiovascular disease is the major cause of mortality in adults and children on chronic dialysis and in adults after kidney transplantation. Cardiovascular disease burden and cardiovascular mortality are high in adults with chronic kidney disease. The early development of cardiovascular disease risk factors, some of which are modifiable, largely explain this phenomenon. Limited data are available on the prevalence of chronic kidney disease in children, the prevalence of cardiovascular disease in children with chronic kidney disease, and the prevalence of cardiovascular disease risk factors in these patients. This article summarizes the current knowledge of the prevalence of cardiovascular disease and of cardiovascular disease risk factors in pediatric patients with predialysis chronic kidney disease. Long-term prospective studies are needed to determine the impact of early identification and treatment of cardiovascular disease and its risk factors on the natural history of cardiovascular disease in children with chronic kidney disease.

Effects of halothane and sevoflurane on QT dispersion in paediatric patients

BACKGROUND

The QT dispersion (QTd) of the ECG is an indirect measure of heterogeneity of ventricular repolarization which may contribute to complex ventricular arrhythmias. We compared the effects of halothane and sevoflurane on QTd, and heart-rate corrected QT dispersion (QTcd).

METHODS

Fifty ASA physical status I patients, aged 5-15 years, undergoing general anaesthesia were studied. A control ECG recording was printed before induction of anaesthesia. In the halothane group, anaesthesia was induced with halothane 4% in 2 : 1 ratio of air : O2 mixture and in the sevoflurane group with sevoflurane 8% in 2 : 1 ratio of air : O2 mixture. The ECG was recorded 1 and 3 min after induction of anaesthesia, 1 and 3 min after the administration of vecuronium 0.08 m.kg(-1) intravenous and 1 and 3 min after the tracheal intubation. All ECGs were analysed by two cardiologists blinded to the anaesthetic.

RESULTS

Although QTd increased in both groups following intubation, this difference was not statistically significant when compared with control values. Following intubation five patients in the halothane group had ventricular arrhythmias of short duration, whereas no arrhythmias were recorded in the sevoflurane group (P = 0.052). Following intubation, QTd (45 +/- 15 ms vs 40 +/- 14 ms) and QTcd (60 +/- 17 ms vs 55 +/- 16 ms) values in the halothane group were significantly greater than the sevoflurane group (P < 0.05).

CONCLUSION

Neither sevoflurane nor halothane caused a significant increase in QTd compared with control values before induction. Only QTd following intubation was significantly greater in the halothane group than the sevoflurane group.

Cardiovascular disease in pediatric chronic dialysis patients

BACKGROUND

Little information is available regarding cardiac morbidity and mortality in children with end-stage renal disease. We sought to determine the incidence of cardiac morbidity and mortality in pediatric chronic dialysis patients.

METHODS

Medicare incident pediatric (0 to 19 years) dialysis patients from 1991 to 1996 were identified from the United States Renal Data System. Study endpoints included development of arrhythmia, valvular heart disease, cardiomyopathy, or cardiac arrest, all causes of death, and cardiac-related death. Statistical analyses were performed using the Poisson regression model and chi-square test.

RESULTS

A total of 1454 children were eligible for inclusion, 452 (31.1%) of whom developed a cardiac-related event. Arrhythmia was the most common event (19.6%) compared with valvular disease (11.7%), cardiomyopathy (9.6%), and cardiac arrest (3%). Arrhythmia and valvular heart disease incidence were increased in 15- to 19-year-olds (P < 0.0001 for both), females (P = 0.004, P = 0.03) and blacks (P < 0.0001, P = 0.002). Cardiomyopathy incidence was increased in blacks (P = 0.001) and tended to be increased in females (P = 0.053). The adjusted annual cardiomyopathy rate during the first 3 years increased between 1991 and 1996 (P = 0.003). Death occurred in 107 patients, and 41 (38%) were cardiac deaths.

CONCLUSIONS

Cardiovascular disease is a significant cause of morbidity and mortality in pediatric chronic dialysis patients. Cardiomyopathy incidence is increasing. Black, female, and adolescent children have increased risk for cardiovascular disease.