Determinants of augmentation of ECG QRS complexes and R waves in patients after hemodialysis

Background: Hemodialysis (HD) leads to an augmentation in the amplitude of QRS complexes (QRS-c), and R waves (R-w); some correlates of this phenomenon have been identified, but the exact mechanism for these ECG changes remains elusive. The objective of this study is to search for the underlying mechanism(s) of the post-HD augmentation of QRS-c and R-w. Methods: The sum of the amplitudes of ECG QRS-c and R-w, along with a host of other parameters (body weight, fluid volumes, echocardiographically-derived left ventricular dimensions and volumes, serum potassium, hemoglobin, hematocrit, and others) was measured, before and after HD, in 17 patients with end-stage renal failure. Results: While there were many correlations noted between the changes in the QRS-c and R-w and some of the above variables in numerous univariate analyses carried out, multivariate analyses did not identify any of the examined variables as exerting an independent influence on the observed ECG changes after HD. Conclusion: Augmentation of QRS-c and R-w following HD is engendered by an interplay of a decrease in the LVEDD/LVEDV, and K+, loss of fluid volume, and a rise in Hb and Ht, without any of the above being an independent variable; also other factor(s) (e.g., increase in the body electrical impedance) exerting an influence in this ECG phenomenon cannot be excluded.