QT dispersion and signal-averaged electrocardiogram in hemodialysis and CAPD patients

Objective: The aim of this study was to compare QT dispersion (QTd) and sig nal-averaged electrocardiogram (SA-ECG) parameters that may predict risk of malignant arrhythmias in patients on hemodialysis (HD), on continuous ambu latory peritoneal dialysis (CAPD), and in controls. Setting: Controlled cross-sectional study in a tertiary-care setting. Patie nts: 28 HD (MIF 18/10; mean age 32 +/- 9 years), 29 CAPD (M/F 17/12; mean a ge 34 +/- 10 years), and 29 healthy controls (M/F 17/12; mean age 32 +/- 8 years) were included. Interventions: On EGG, minimum (QTmin) and maximum (QTmax) QT duration and their difference (QTd) were measured. In SA-ECG, duration of filtered QRS, HFLA signals less than 40 muV, and RMS voltage (40 ms) were also measured. Results: Higher serum Ca2+ and lower K+ levels were found in CAPD compared to HD. All QT parameters were increased in HD and CAPD compared to controls . QT dispersion was significantly prolonged in HD compared to CAPD. In HD, QTd was correlated with left ventricular (LV) mass index (r = 0.53, p = 0.0 04), but not in CAPD (r = -0.09, p = 0.63). QT dispersion was significantly prolonged in patients with LV hypertrophy compared to patients without hyp ertrophy on HD (68 +/- 18 ms vs 49 +/- 18 ms, p = 0.008). In the analysis o f SA-ECG, 3 of the 28 (11%) HD and 2 of the 29 (7%) CAPD patients had abnor mal late potentials. Patients on HD and CAPD had significantly higher filte red-QRS duration compared to controls (105 +/- 15 ms and 104 +/- 12 ms vs 9 5 +/- 5 ms, respectively, p = 0.04). Patients with LV hypertrophy had highe r filtered-QRS duration compared to patients without hypertrophy (109 +/- 1 2 ms vs 95 +/- 8 ms, p < 0.001). Conclusion: Dialysis patients had prolonged QTd and increased filtered-QRS duration in SA-ECG compared to controls. Patients on HD had longer QTd than patients on CAPD. QTd has been correlated to LV mass index in HD, but not in CAPD. This difference might be due to the effeet of different dialysis m odalities on electrolytes, especially the higher serum Ca2+ levels.