|Year : 2014 | Volume
| Issue : 3 | Page : 524-529
|QT dispersion in the electrocardiogram in hemodialysis and peritoneal dialysis patients
Sadraddin Rasi Hashemi1, Hamid Noshad1, Iman Yazdaninia2, Bahram Sohrabi3, Ahmad Separham3
1 Chronic Kidney Disease Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
2 Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
3 Cardiovascular Research Center of Tabriz University of Medical Sciences, Tabriz, Iran
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|Date of Web Publication||9-May-2014|
| Abstract|| |
To evaluate QT dispersion (QTd) in dialysis patients in an analytic cross-sectional study, three groups were enrolled: Hemodialysis (HD), peritoneal dialysis (PD) and control (30 patients in each group) to study QT parameters in 12-lead electrocardiograms (ECGs). QTd was calculated (maximum QT interval minus minimum QT interval in different leads in each ECG). In dialysis patients, left ventricle mass index (LVMI) was also evaluated using the ECG of the patients. QT, corrected QT (QTc), QTd and QTc dispersion were significantly higher in the HD and PD groups than in controls, but there was no difference between the dialysis groups. There was no difference between the HD and the PD groups in LVMI and ejection fraction. In the PD group, there was a positive correlation of LVMI and QTd (r = 0.5, P = 0.004) and QTc dispersion (r = 0.54, P = 0.004). We conclude that the QT changes were more prominent in HD and PD patients than in controls, which could be due to electrolyte changes. Further studies to evaluate the causes of the QT changes in a larger population are needed.
|How to cite this article:|
Hashemi SR, Noshad H, Yazdaninia I, Sohrabi B, Separham A. QT dispersion in the electrocardiogram in hemodialysis and peritoneal dialysis patients. Saudi J Kidney Dis Transpl 2014;25:524-9
|How to cite this URL:|
Hashemi SR, Noshad H, Yazdaninia I, Sohrabi B, Separham A. QT dispersion in the electrocardiogram in hemodialysis and peritoneal dialysis patients. Saudi J Kidney Dis Transpl [serial online] 2014 [cited 2020 May 31];25:524-9. Available from: http://www.sjkdt.org/text.asp?2014/25/3/524/132159
| Introduction|| |
Cardiovascular diseases are among the most important mortality risk factors in dialyzed patients. It is responsible for 50% of deaths in chronic dialysis patients. , Cardiac arrhythmias are common in hemodialysis (HD) patients, especially during and immediately after dialysis. , These arrhythmias may appear due to rapid changes in intra- and extracellular electrolyte contents. , Early detection of at-risk patients is necessary.
QT interval dispersion (QTd) is recently mentioned as a predictive factor in life-threatening ventricular arrhythmias. QTd is simply the interval difference between the shortest and the longest QT interval in a 12-lead electro-cardiogram (ECG). ,
QTd is a marker of ventricular repolarization changes and can be seen in high-risk patients such as those with diabetes, heart failure  and essential hypertension. 
QTc (corrected QT) dispersion is related to some life-threatening arrhythmias.  Increasing of QTd was reported in HD patients, , and some studies of peritoneal dialysis (PD) patients, , while other studies of PD patients did not show these changes. , Inter- and intrapatient variation in incidence is observed in the HD patients. ,
QT dispersion reflects bipolar projection of the heart and morphological abnormalities of T wave. ,, The normal range of QT dispersion is 40-50 ms, and QT dispersion higher than 65 ms in the general population  and higher than 74 ms in the HD patients are associated with life-threatening ventricular arrhythmias.  Interstitial fibrosis of the myocardium with calcium deposition was associated with higher QT dispersion in these patients. ,
The aim of our study was the evaluation of the prevalence of QT dispersions in HD and PD patients, with the determination of the possible causes of such changes.
| Methods|| |
Three separate groups of patients (each one consists of 30 patients) were enrolled in this study (HD, PD and controls).
We excluded from the study patients with bundle branch block (BBB) or atrial fibrillation, patients who were treated with QT interval influencing drugs such as quinidine and procainamide and patients with previous history of heart failure, ischemic heart disease, amyloidosis and diabetes mellitus. Dialyzed patients had, at least, a 6-month history of HD or PD.
Demographic characteristics including age, sex, dialysis duration, dialysis sessions per week, blood pressure, blood urea nitrogen (BUN), creatinine (Cr), potassium (K), calcium (Ca), phosphorus (P), serum albumin, parathormone (PTH) and underlying chronic kidney damage were recorded. Blood pressure was measured before dialysis. Blood samples for BUN, Cr and electrolytes (K, Ca) were collected and QT interval was measured simultaneously. Echocardiography was performed for calculating of left ventricular (LV) mass and LVMI.
QT parameters were measured using 12-lead ECG, which was obtained at a speed of 50 mm/s. All ECGs were encoded and sent to a cardiologist for analysis.
QT interval was measured from the beginning of the QRS complex to the end of the T wave. Three QT intervals were measured in each 12-lead ECG and the mean value was recorded.
QT dispersion (QTd) was defined as the difference of the highest and the lowest value of the QT interval in the same 12-lead ECG. Each QT interval was corrected (QTc) for heart rate according to the Bazett formula (QTc = QT/√RR), QTd greater than 50 was considered abnormal.
A written consent was taken from the enrolled patents.
| Statistical Analysis|| |
All data were analyzed using the statistical package SPSS version 16.0. Before starting analysis, normal distribution of the variables was proven by the Kolmogorov-Smirnov test. One-way analysis of variance (ANOVA) and Student's t-test were used for comparing the studied groups. Post hoc and Tukey's HSD were used for clarifying the significance. The significance level was considered as P <0.05.
| Results|| |
The mean age of the study patients was 49.72 ± 10.12 years. Fifty patients (55.6%) were male and 40 patients (44.4%) were female. There was no significant difference in the age and sex among the studied groups.
The mean systolic blood pressure was 129 ± 18.3 in the controls, 128 ± 20.0 in the HD and 131.4 ± 16.6 mm Hg in the PD groups (P = 0.45). The mean diastolic blood pressure was 75.9 ± 10.1 in the controls, 74.8 ± 11.1 in the HD group and 77.0 ± 9.15 mm Hg in the PD group (P = 0.41).
Laboratory data are summarized in [Table 1]. It is clear that serum P, BUN, Cr, albumin, ferritin and iPTH levels were higher in the HD patients. On the other hand, the serum cholesterol levels were higher in the PD patients.
There was a statistical difference between the mean of the QT and QTc intervals and QTd and corrected QTd (QTdc) in all the groups [Figure 1], [Figure 2], [Figure 3] and [Figure 4]. These parameters did not significantly differ in the patients of the HD and the PD groups, but they were significantly higher than those in the patients of the control group (P <0.001).
The mean LV mass in the HD and PD patients was 178 ± 63.7 g and 177 ± 70.7 g, respectively (P = 0.97). The mean LVMI in the HD and the PD patients was 107 ± 34.8 g/ m 2 and 109 ± 56.5 g/m 2 , respectively (P = 0.84). The mean left ventricular ejection fraction (LVEF) in the HD and the PD patients was 50.7% ± 3.40 and 48.7% ± 4.30, respectively (P = 0.89).
There was no significant correlation between the LVMI and the QTd in the HD patients, but there was a significant positive correlation between these parameters in the PD patients (r = 0.51 and P = 0.004). However, there was a positive correlation of the QTc with LVMI in only the PD patients (r = 0.56, P = 0.004).
| Discussion|| |
Some studies found that patients with end-stage renal disease (ESRD) have higher QTc and QTdc. , Maule et al showed that patients with ESRD have higher QTc, but QTd was similar to the control group.  Wu et al reported that QTdc is significantly higher in PD patients.  Our study did not show a difference between the HD and the PD groups. Dervifloglu et al showed that HD patients have higher QTc intervals compared with the controls.  Yildiz et al also showed that all QT parameters are higher in HD and PD patients.  Like others, our study showed that QTd was higher in the HD and the PD patients compared with controls.
According to above-mentioned data, both the HD and PD patients have a remarkable pre-disposition to cardiac arrhythmias. 
According to Yildiz et al, serum calcium levels are higher and serum potassium levels are lower in the PD patients.  Kantarci et al reported that there was no significant difference in the BUN, Cr, Na, Ca and PTH levels between the HD and PD patients, but serum K levels were significantly more elevated in the HD patients.  In our study, serum P, BUN, Cr, albumin, ferritin and iPTH levels were higher in the HD patients and there were no significant differences in the serum levels of Na, K and Ca between the HD and the PD patients.
Gunal et al showed that there is no difference between blood pressure and cardiothoracic indices in PD and HD patients,  and there is no difference between systolic and diastolic blood pressure of both dialysis groups.
Takeda et al revealed that LVMI was higher in PD compared with HD patients in a short-term study, but deteriorated gradually in the long-term follow-up.  Furthermore, others have found that LVMI was significantly higher in the HD group.  In our study, we could not find any significant difference between the HD and PD groups in the LVMI and the LVEF; Gunal et al reported similar results. 
It is reported that increasing QTd directly correlates with LVMI of hypertensive patients.  Recently, a similar correlation was reported in the HD patients.  Yildiz et al showed that QTd has a positive correlation with LVMI in only HD patients.  In contrast, we found a positive correlation between LVMI and QTd and QTc dispersion in only the PD patients.
Wu et al found elevated QTdc more than 75 ms among 102 non-diabetic PD patients, lower blood pressure, lower left ventricular mass, lower serum albumin and higher serum levels of Ca and transferrin than controls.  Elevated Fe amounts of the myocardium may be associated with higher QT intervals and cardiac arrhythmias. ,
Dervifloglu et al studied the correlation of Fe reservoirs and QTc in HD patients. They found that elevated serum Fe levels had a significant correlation with higher QTc, but not TIBC and ferritin.  In our study, there were no significant differences of all these parameters between the HD and PD groups compared with the control group.
Kirvela et al found that QTdc was more common in diabetic and non-diabetic uremic patients than controls.  In addition, Maule et al studied 69 patients with ESRD and found higher QTc and QTd in them; QTc was higher than 44 ms in 33.3% of the patients. 
Tian revealed that LVMI was significantly higher in HD than in PD patients; the prevalence of LVH (left ventricular hypetrophy) was 68.8% in HD and 45.2% in PD patients. They also found that systolic blood pressure and type of dialysis (HD or PD) were independent predictors of LVMI. 
In conclusion, we found in our study that QT interval changes in the ECG were more significant in the HD and PD patients. We also found a positive correlation between LVMI and QTdc in only PD patients. Other studies with greater sample sizes are required to confirm our results.
Conflict of interest: None
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Dr. Bahram Sohrabi
Department of Cardiology, Shahid Madani Center, Tabriz University of Medical Sciences, Tabriz
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
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