Hemodialysis changes the QRS amplitude in the electrocardiogram.

We studied eight patients to determine whether changes occur in the QRS amplitude when these patients are submitted to hemodialysis. The following variables were assessed before and after each (N = 28) hemodialysis session: (1) plasma sodium and potassium concentrations, (2) QRS amplitude, (3) the heart rate and its variability, (4) ventricular volumes, ventricular mass, ejection fraction and circumferential fiber shortening, (5) arterial pressure and end systolic stress, and (6) body weight. QRS amplitude was computed as the algebraic sum of the positive and negative waves of each QRS complex of the electrocardiogram. QRS amplitude changes were compared to body weight, ventricular volumes, ventricular mass, ejection fraction, circumferential fiber shortening, plasma potassium and sodium concentrations, arterial pressure, end systolic stress, heart rate, and R-R variability. After the hemodialysis sessions we found a significant increase (P = 0.0006) in QRS amplitude and a significant decrease in body weight (P = 0.0001), end diastolic volume (P = 0.043), plasma potassium concentration (P = 0.000001), end systolic stress (P = 0.025) and systolic arterial pressure (P = 0.023). Hemodialysis did not produce significant changes in the other variables. The statistical analyses performed did not show any significant influence of any of the measured variables on the QRS amplitude change. The QRS amplitude increases after hemodialysis but the cause of this increase is still unclear.