Effect of hemodialysis on the signal-averaged electrocardiogram

The presence of late potentials (LPs) on signal-averaged electrocardiography (SAECG) is predictive of ventricular tachycardia. The effect of hemodialysis (HD) on SAECG has not been well studied. SAECG was evaluated in 28 patients with chronic renal failure immediately before and after HD. In each SAECG, QRS duration, low-amplitude signal duration (LASd), and root-mean-square voltage of the terminal 40 milliseconds of the QRS (RMS40) were measured. To evaluate the effect of fluid removal on SAECG, the last 12 patients were studied during two different HD sessions, one with and one without fluid removal. Two-dimensional echocardiography was performed before and after HD on these 12 patients. At baseline, four patients met the criteria for LPs on SAECG. Only one patient met the criteria for LPs on SAECG after HD. After HD, the mean LASd decreased (28.3 ± 12.9 to 24.9 ± 10.1 milliseconds; P = 0.041) and RMS40 increased (63.0 ± 56.9 to 79.0 ± 59.2 μV; P = 0.006). Among the 12 patients who underwent HD with and without fluid removal, left ventricular end-diastolic dimension decreased with (5.4 ± 0.6 to 5.1 ± 0.6 cm; P = 0.024) but not without fluid removal (5.2 ± 0.3 to 5.1 ± 0.4 cm; P = not significant [NS]). RMS40 improved with (43.8 ± 23.1 to 53.2 ± 22.6 μV; P = 0.03) but not without fluid removal (51.0 ± 26.5 to 51.5 ± 24.2 μV; P = NS). A significant negative correlation was found between change in body weight and change in RMS40 parameter ( r = 0.456; P = 0.0381). SAECG parameters are abnormal in a significant proportion of patients with chronic renal failure and improve with HD despite electrolyte and other proarrhythmic changes. Decreased left ventricular dimension because of fluid removal during HD is one possible explanation for this improvement.