#570 A study of QTc time trends and factors affecting QTc changes during dialysis

Abstract

Abstract Background and Aims Several studies have revealed the relationship between an abnormal QTc interval and mortality with sudden death in patients undergoing haemodialysis (HD). The QTc interval in HD is regulated by several factors, such as electrolytes, pH, and drugs. However, few studies have investigated the changes in the QTc interval during HD sessions and the determining factors. Therefore, we investigated the relationship between changes in electrolytes and QTc interval during HD. Method In this cross-sectional study, 53 patients undergoing maintenance HD were enrolled. Electrocardiogram and blood samples were obtained two days after dialysis. QTc was measured every hour from the start of the HD session, and blood samples were collected at the start, 2 h after, and at the end of the HD session. At the start of the HD session, we measured the blood levels of urea nitrogen, creatinine, β2-microglobulin (β2MG), HCO3-, albumin, intact-parathyroid hormone, phosphorus, Ca, Mg, and K. Blood Ca, Mg, K, and HCO3- levels were evaluated at the start, 2 h after, and at the end of the HD session. The relationship between changes in the QTc interval and various parameters was analysed by Spearman correlation analysis and multiple regression analysis. Results The patients were aged 37–91 (median; 71.5) years, and the duration of dialysis was 1–402 months (median; 2 months). Of the patients, 40.4% were diagnosed as the prolonged QTc interval (≥460 ms) at the start of HD (median; 455 ms). Conversely, 15.9% of patients at 2 h after the start of HD (median; 444 ms) and 8.4% of patients at end of HD (447 ms) were normalized in QTc interval. The peak change in the QTc interval occurred 2 h after start of HD. Thus, we estimated the factors that affected the change in QTc 2 h after the start of dialysis (ΔQTc2h). The duration of HD treatment (r = 0.312, P = 0.025) and serum levels of β2MG (r = 0.324, P = 0.019) were positively correlated with ΔQTc2h. The 2-h change in corrected Ca (ΔcCa2h) (r = −0. 31, P = 0.03) and intact-PTH (r = −0.30, P = 0.035) were negatively correlated with ΔQTc2h. We found no significant correlation between ΔQTc2h and changes in K and Mg. According to the multiple regression analysis, ΔcCa2h (β = −0.293, P = 0.033) and β2MG (β = 0.271, P = 0.042) were significant predictors of ΔQTc2h. Conclusion We anticipated that QTc interval might be prolonged due to the decreased serum K and Mg levels via HD treatments. However, QTc levels during HD were shortened according to increased serum Ca levels. Among the electrolyte levels, the change in blood Ca was significantly correlated with the change in the QTc interval but not with the change in Mg and K. The study results suggest the importance of optimal dialysate electrolytes composition to prevent adverse events and premature death caused by abnormalities in the QTc interval.