RENAL DATA FROM THE ARAB WORLD
|Year : 2020 | Volume
| Issue : 3 | Page : 639-646
|Evaluation of electrocardiographic findings before and after hemodialysis session
Hela Jebali1, Hiba Ghabi2, Ikram Mami2, Lilia Ben Fatma2, Wided Smaoui2, Badr Ben Kaab2, Madiha Krid2, Manel Ben Hlima3, Tasnim Ben Ayed3, Omar Guermazi3, Mohamed Sami Mourali3, Soumaya Beji2, Mohamed Chermiti4, Loumi Zied4, Hanene Kateb5, Mohanad Hassan6, Fethi Ben Hmida6, Lamia Raies2, Mohamed Karim Zouaghi2
1 Department of Nephrology, Rabta Hospital; Faculty of Medicine, Tunis, Tunisia
2 Department of Nephrology, Rabta Hospital, Tunis, Tunisia
3 Department of Cardiology, Rabta Hospital, Tunis, Tunisia
4 Department of Nephrology, Kef Hospital, Kef, Tunisia
5 Department of Nephrology, Manouba Hospital, Manouba, Tunisia
6 Department Laboratory Research of Kidney Pathology (LR00SP01), Charles Nicolle Hospital, Tunis, Tunisia
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|Date of Submission||31-May-2019|
|Date of Acceptance||11-Jul-2019|
|Date of Web Publication||10-Jul-2020|
| Abstract|| |
Dialysis patients have higher rates of sudden cardiac death. The study of the electrocardiogram could identify patients at risk of developing rhythm disorders. The aim of this study was to evaluate the electrocardiographic findings before and after the hemodialysis (HD) session and to examine associations of clinical and serum electrolytes with electrocardiogram findings. We conducted a multicentric transversal study, including chronic HD patients during January 2018. Standard 12-lead electrocardiogram was recorded, before and after the HD session. A medical history was documented. It included age, gender, initial nephropathy, and comorbidities. Serum potassium and total serum calcium were measured before a routine HD session. Serum potassium was measured after HD session. Corrected QT for heart rate was calculated using Bazett’s formula. The study included 66 patients. Nineteen patients (28.8%) had hyperkalemia before the HD session and 44 (66.7%) patients had hypokalemia after the HD session. Seventeen patients had prolonged QTc interval (25.7%). On multiple regression analysis, only the prolonged QTc interval was significantly correlated with the serum potassium (P = 0.046).When comparing the mean values of electrocardiogram parameters before and after the HD session, we noted a significant change of heart rate (P = 0.001), R wave (P = 0.016), T wave (P = 0.001), and T/R (P = 0.001) wave. Delta K+ did not correlate with the change in T wave amplitude (r = 0.23, P = 0.59), R wave amplitude (r = –0.16, P = 0.2), T/R wave (r = 0.055, P = 0.65), or QRS duration (r = 0.023, P = 0.85). Delta QTc was correlated to ΔK+. We conclude that usual electrographic manifestations of hyperkalemia are less pronounced in HD patients. Our results confirmed the unstable status of cardiac electrophysiology during HD session.
|How to cite this article:|
Jebali H, Ghabi H, Mami I, Fatma LB, Smaoui W, Kaab BB, Krid M, Hlima MB, Ayed TB, Guermazi O, Mourali MS, Beji S, Chermiti M, Zied L, Kateb H, Hassan M, Hmida FB, Raies L, Zouaghi MK. Evaluation of electrocardiographic findings before and after hemodialysis session. Saudi J Kidney Dis Transpl 2020;31:639-46
|How to cite this URL:|
Jebali H, Ghabi H, Mami I, Fatma LB, Smaoui W, Kaab BB, Krid M, Hlima MB, Ayed TB, Guermazi O, Mourali MS, Beji S, Chermiti M, Zied L, Kateb H, Hassan M, Hmida FB, Raies L, Zouaghi MK. Evaluation of electrocardiographic findings before and after hemodialysis session. Saudi J Kidney Dis Transpl [serial online] 2020 [cited 2021 Jul 26];31:639-46. Available from: https://www.sjkdt.org/text.asp?2020/31/3/639/289450
| Introduction|| |
Cardiovascular mortality is frequent in patients with end-stage renal disease. Several risk factors may contribute to the increased risk of sudden cardiac death in this population. Electrolyte disorders and dialysis treatment are considered as arrhythmogenic stimuli.,
It is recognized that the study of the electrocardiogram (ECG) in the general population is useful for the management of cardiovascular complications. Among hemodialysis (HD) patients, there are substantial disparities in the identification of the factors leading to electro-graphic abnormalities observed.
An increase of the QT interval is a marker of ventricular repolarization defects and thus it is associated with an increased risk for arrhythmias. Several studies have noted that QT prolongation is more common in chronic HD patients. Genetic polymorphisms and the rapid declines in serum potassium, magnesium, and calcium, coupled with frequent exposure to drugs that cause QT prolongation, may contribute to the high frequency of this electro-graphic abnormality in this population. On the other hand, the place of the ECG in the evaluation of the severity of hyperkalemia in dialysis patients is debatable. The aims of the present study were therefore two folds. First, we assessed the effect of the HD session on ECG findings and particularly on the QT interval. Secondarily, we examined the associations of clinical and serum electrolytes with ECG findings.
| Methods|| |
We conducted a multicentric transversal study, including chronic HD patients in the Nephrology Department at La Rabta Hospital, Kef Hospital and Manouba Hospital during January 2018. We included patients undergoing HD for more than three months and older than 18 years. All patients had undergone standard maintenance HD (4 h, 3 times/ week). HD was performed using a polysulfone membrane and bicarbonate dialysate. Sodium in dialysate was 138 mmol/L, potassium was 2.0 mmol/L, and calcium was 1.5 mmol/L.
We did not include patients with pacemaker or cardiac disease and patients under chronic treatment that can lead to a prolonged QT interval. We excluded patients who had bundled branch block, atrial fibrillation, or flutter.
Informed consent was obtained from all the participants. A clinical history was documented to include age, gender, initial nephropathy, and duration of chronic HD. Serum potassium and total serum calcium were measured in a blood sample obtained just before a routine HD session. Serum potassium was measured after the HD session.
Ten minutes before and after the HD session, 12-lead electrocardiographs were performed at 10 mm equals to 1 mv at 25 mm/s. A senior cardiologist who was blinded to the clinical status and the biological parameters of the patients reviewed the ECGs. The QT interval was measured manually with a caliper from the onset of the QRS complex to the end of T wave. Corrected QT for heart rate was calculated using Bazett’s formula by dividing the QT interval by the square root of R-R interval. QTc was consi-dered prolonged if QTc interval was about 450 ms or longer in males and of 460 ms or longer in females. T waves and R wave amplitude were measured in the chest leads, and then T/R ratio was calculated. QRS complex duration was measured, and the presence of U wave was sought.
- Hyperkalemia was defined as serum potassium ≥5.5 mmol/L
- Hypokalemia was defined as serum potassium <3.5 mmol/L
- Hypocalcemia was defined as serum calcium <90 mg/L.
Delta (Δ) Potassium = Pre-HD serum potassium – post-HD serum potassium.
Delta (Δ) QTc = Pre-HD QTc interval – post- HD QTc interval.
Delta (Δ) T/R = Pre-HD T/R – Post-HD T/R.
| Statistical Analysis|| |
Statistical analyses were performed with the IBM SPSS Statistics for Windows version 20.0 (IBM Corp., Armonk, NY, USA). Quantitative variables were expressed as means ± standard deviations. Qualitative variables were presented by frequency and percentages. The data were assessed with regard to the distribution using the Shapiro–Wilk normality test. To assess differences between quantitative variables, we used the t-test or Mann–Whitney U-test when appropriate. To analyze differences between repeatedly measured variables, we used paired-samples t-test. To compare categorical variables, we used the Chi-square or Fisher’s exact test. Correlation coefficients and significance were calculated from Pearson’s test or Spearman’s test when appropriate. The multivariate logistic regression test was used to identify variables independently associated with the different ECG findings. P <0.05 was considered statistically significant.
| Results|| |
The study included 66 patients. Predominant etiologies of end-stage renal disease were diabetic nephropathy (24%), glomerulonephritis (16%), and hypertensive nephrosclerosis (12%). All these patients had an arteriovenous fistula as a vascular access. [Table 1] shows the demographic, clinical, and laboratory characteristics of the study population. Nineteen patients (28.8%) had hyperkalemia before the HD session, and 44 (66.7%) patients had hypokalemia after the HD session. Twenty-eight patients (42.4 %) had hypocalcemia with a mean serum calcium of 77.36 ± 8.49 mg/L.
The patients were classified into two groups according to pre-HD potassium, as shown in [Table 2]. No differences were associated with gender, age, diabetes, HD duration, or calcium level between the two groups. Hyperkalemia was not correlated to any of the above-studied ECG parameters except a negative correlation with QTc interval (r = –0.3; P = 0.038).
|Table 2: Clinical and electrocardiogram findings according to prehemodialysis kalemia.|
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Seventeen patients had prolonged QTc interval (25.7%). We found, in univariate study, that these patients had lower level of potassium (4.67 ± 0.50 mmol/L vs. 5.11 ± 0.70 mmol/L; 0.001) and higher level of calcium (84.14 ± 13.36 mmol/L vs. 83.62 ± 6.60 mmol/ L; NS). We found no significant differences related to age, gender, hypertension, or diabetes. When comparing the frequency of QTc according to the duration of HD (≤24 months vs. >24 months), we did not find any difference. On multiple regression analysis, the prolonged QTc interval was statistically significantly correlated with the serum potassium (P = 0.046).
Concerning ECG findings after the HD session, univariate analysis did not reveal any significant correlation between the studied electrographic signs and hypokalemia or the ΔK+ [Table 3].On the other hand, the presence of the U wave was more frequent in patients with hypokalemia.
|Table 3: Electrocardiogram findings according to kalemia after hemodialysis session.|
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When comparing the mean values of ECG parameters before and after the HD session, we noted a significant change of heart rate, R wave, and T wave [Table 4].
|Table 4: Electrocardiogram findings before and after hemodialysis session.|
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Delta QTc was correlated to ΔK+ (r = 0.27, P = 0.027) [Figure 1]. ΔK+ did not correlate with the change in T wave amplitude (r = 0.23, P = 0.59), R wave amplitude (r = –0.16, P = 0.2), T/R wave (r = 0.055, P = 0.65), or QRS duration (r = 0.023, P = 0.85). Otherwise, the ultrafiltration rate was associated with delta T/R wave (r =0.25; P = 0.04) [Figure 2].
| Discussion|| |
In this study, hyperkalemia was noted in 28.8% of cases. We did not find a correlation between the value of the serum potassium and the electrographic abnormalities. Our results confirmed that usual electrographic manifestations of hyperkalemia are less pronounced in HD patients.
The increasing prevalence of cardiovascular mortality in HD patients is a global public health concern.
Hyperkalemia is considered as a life-threatening disorder for chronic HD patients. It is associated with a high risk of mortality.
Several hypotheses have been advanced to explain the lack of correlation between serum potassium and electrocardiographic findings among HD patients. Indeed, the serum potassium concentration does not reflect the ratio between intracellular and extracellular potassium in HD patients, which is the determining factor in the repolarization of the membrane. Added to that, there are complex disturbances of pH and electrolytes, including that of calcium and magnesium, which can mask the expression of hyperkalemia. One other possible explanation is that the rate of potassium elevation, which is usually slow in chronic HD patients, is more relevant than the present value of serum potassium. Hence, ECG is an unreliable means of detecting potentially lethal hyperkalemia among HD patients.
The prolonged QT interval is another predictor of cardiovascular mortality in HD patients. It reflects the cardiac repolarization time. Thereby a prolonged QT interval signs a cardiac repolarization defect. It was associated with a high risk of sudden cardiac death. Several factors may result in a prolonged QT interval. Electrolyte disturbance frequently observed in HD patients is one of these factors. That is why it seems justified to assess changes in the QTc interval among this population. In our study, 25% of patients had prolonged QTc interval. This prevalence is lower than that reported in the literature. The prevalence of prolonged QT among HD patients is about 50%, according to previous studies., We thought that there were two reasons for this disparity. First, patients taking QT-prolonging agents and those with conduction and rhythm abnormalities were not included in our study. Second, our patients had a relatively young age compared to patients enrolled in other studies. In fact, Reardon and Malik found that older patients have longer QTc interval. The mean age of our patients was 52.11 ± 14.15 years. Nie et al found that the prevalence of prolonged QTc was about 65% among chronic HD patients with a mean age of 60.87 ± 15.73 years. A disturbance of the autonomic nervous system may explain this finding.
We did not find a correlation between pre- HD QTc interval and serum calcium. We did not measure ionized calcium, which may explain this lack of a statistically significant correlation. It is admitted that ionized calcium rather than the total calcium is responsible for the biologic effect of calcium such as cardiac function. Usually, total serum calcium reflects the calcium status because there is a stable balance between bound and free calcium. In HD patients, this balance is disturbed because they have other metabolic disorders (acidosis and hypoalbuminemia), which justifies the importance of the measurement of ionized calcium.
On the other hand, Matsumoto et al reported that the QTc interval becomes prolonged along with the HD duration. In our study, we did not find the impact of the HD duration of the QTc interval.
When comparing ECGs before and after the HD session, we found a slight tendency of QTc interval to be decreased in post-HD. The impact of HD on QTc interval remains debatable. Several studies reported a progressive increase of QTc interval during HD,, while in the other studies, QTc interval decreased or did not change. The decline in serum potassium seems to influence QTc interval. We found a significant correlation between delta QTc and delta potassium. Prolonged QTc in post-HD session was more frequent in patients with hypokalemia. These findings are similar to the results reported by Nie et al. We found a significant increase in the R wave amplitude and a significant decrease in the T wave amplitude and the T-to- R ratio after the HD session .These differences reflect the unstable status of cardiac electrophysiology during HD.
We noted a significant correlation between ultrafiltration rate and delta T/R wave ratio. Ozportakal et al have assessed the relationship between UF and ECG parameters. The decline in myocardial tissue perfusion, induced by ultrafiltration, may explain these results.,
Our study has some limitations. First, the number of enrolled patients was small, which constrain the conclusions. Second, we did not measure ionized calcium and finally our results did not include ECG monitor during the whole HD session.
| Conclusion|| |
HD patients with severe hyperkalemia may not manifest any ECG changes. Convention 12-lead electrocardiography is a reasonable method for assessment of the QT interval.
| Acknowledgments|| |
We thank the co-medical staff of the HD centers, whose support and warm encouragement were inestimably valuable throughout the course of our study.
Conflict of interest: None declared.
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Department of Nephrology, Rabta Hospital, Tunis
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]