Hemodialysis-induced repolarization abnormalities on ECG are influenced by serum calcium levels and ultrafiltration volumes

Abstract

Hemodialysis (HD) patients are known to have high cardiovascular mortality rate. Sudden cardiac death (SCD) due to arrhythmias causes most of the cardiac deaths. HD per se may lead to ECG abnormalities and ventricular arrhythmias. Monitoring ECG parameters such as corrected QT interval, QT dispersion (QTd), Tpe interval may be useful to stratify the patients with high risk of arrhythmia and SCD. Herein we aimed to investigate the effects of changes in serum electrolyte levels and pH on ECG parameters before and after the HD. A total of 50 chronic HD patients (mean age 58 +/- 19; male 27) were enrolled. Patients with unmeasurable T waves; atrial fibrillation; bundle branch block; use of class I or class III antiarrhythmic drugs were excluded. Serum potassium, magnesium, calcium, urea, creatinine and pH were measured before and after HD treatment. Standard surface 12-lead ECGs were recorded before and after HD. QTc, QTd, Tpe, JT interval, P-wave-duration, P-wave dispersion were determined. Serum potassium and magnesium decreased, and calcium, pH and bicarbonate levels increased; QRS and Tpe interval were increased after HD. Basal Tpe was correlated with urea (r = 0.31, p = 0.02). Tpe interval was higher in hypocalcemic compared to normocalcemic patients (77 +/- 11 vs 70 +/- 9 ms, p = 0.02). a dagger Tpe was correlated with a dagger calcium (r = -0.32, p = 0.02). Basal QTc was correlated with calcium (r = -0.62, p < 0.001). a dagger QTc was correlated with basal calcium (r = 0.39, p = 0.005) and a dagger calcium (r = -0.46, p < 0.001). Basal JT was correlated with calcium (r = -0.55, p < 0.001). a dagger JT was correlated with pH (r = 0.35, p = 0.01), a dagger calcium (r = -0.53, p < 0.001) and a dagger magnesium (r = -0.30, p = 0.03). Before HD, 12 patients (12%) were hypermagnesemic of whom JT intervals were lower (314 +/- 20 vs 332 +/- 23 ms, p = 0.02). Ultrafiltration per body weight was associated with a dagger QTc (r = -0.40, p = 0.007) and a dagger JT (r = -0.36, p = 0.01). QRS and Tpe intervals were increased after HD. Tpe interval was longer in hypocalcemic patients. Change in Tpe was negatively associated with the change in calcium. Ultrafiltration was associated with a dagger QTc and a dagger JT. Calcium and ultrafiltration seem to be the most important determinants of ECG parameters of HD-induced repolarization abnormalities.