Electrocardiographic Abnormalities and QT(c) Interval in Patients Undergoing Hemodialysis

BACKGROUND: Sudden cardiac death is one of the primary causes of mortality in chronic hemodialysis (HD) patients. Prolonged QT(c) interval is associated with increased rate of sudden cardiac death. The aim of this article is to assess the abnormalities found in electrocardiograms (ECGs), and to explore factors that can influence the QT(c) interval. METHODS: A total of 141 conventional HD patients were enrolled in this study. ECG tests were conducted on each patient before a single dialysis session and 15 minutes before the end of dialysis session (at peak stress). Echocardiography tests were conducted before dialysis session began. Blood samples were drawn by phlebotomy immediately before and after the dialysis session. RESULTS: Before dialysis, 93.62% of the patients were in sinus rhythm, and approximately 65% of the patients showed a prolonged QT(c) interval (i.e., a QT(c) interval above 440 ms in males and above 460ms in females). A comparison of ECG parameters before dialysis and at peak stress showed increases in heart rate (77.45±11.92 vs. 80.38±14.65 bpm, p = 0.001) and QT(c) interval (460.05±24.53 ms vs. 470.93±24.92 ms, p<0.001). After dividing patients into two groups according to the QT(c) interval, lower pre-dialysis serum concentrations of potassium (K(+)), calcium (Ca(2+)), phosphorus, calcium* phosphorus (Ca*P), and higher concentrations of plasma brain natriuretic peptide (BNP) were found in the group with prolonged QT(c) intervals. Patients in this group also had a larger left atrial diameter (LAD) and a thicker interventricular septum, and they tended to be older than patients in the other group. Then patients were divided into two groups according to ΔQT(c) (ΔQT(c) = QT(c peak-stress)- QT(c pre-HD)). When analyzing the patients whose QT(c) intervals were longer at peak stress than before HD, we found that they had higher concentrations of Ca(2+) and P(5+) and lower concentrations of K(+), ferritin, UA, and BNP. They were also more likely to be female. In addition, more cardiac construction abnormalities were found in this group. In multiple regression analyses, serum Ca(2+) concentration before HD and LAD were independent variables of QT(c) interval prolongation. UA, ferritin, and interventricular septum were independent variables of ΔQT(c). CONCLUSION: Prolonged QT interval is very common in HD patients and is associated with several risk factors. An appropriate concentration of dialysate electrolytes should be chosen depending on patients’ clinical conditions.