Changes in QT interval before and after hemodialysis

Background : Cardiovascular mortality and morbidity are high in chronic renal failure (CRF) patients. Increased dispersion of QT intervals is known to predispose to ventricular arrhythmias and sudden cardiac death. This study was conducted to assess the effect of hemodialysis (HD) on corrected QT (QTc) intervals and their dispersions (QTd) in chronic hemodialyzed patients.

Fifty-eight patients ( mean age 54.2±15.8 years) with chronic renal disease on chronic hemodialysis (HD) were assessed by standard examination including blood pressure, body weight, heart rate, 12-lead electrocardiography and laboratory tests like electrolytes (Na (+), K (+), Ca (++), phosphate), urea, and creatinine 30 minutes before and after HD. The QT intervals and QTc QTc= QT √R-R/ (in milli seconds [ms]) for each lead were measured manually by one observer using calipers. The difference between the maximum and the minimum of QT interval was noted as QT dispersion (QT d).

The mean of pre and post dialysis R-R intervals was 859.22±96.85 ms and 870.43±91.45 ms, respectively (p>0.05). The mean of corrected QT cmax intervals increased significantly from 423.45±24.10 to 454.41±30.25 ms (p<0.05). The mean of QT dispersions and the corrected QT interval dispersions changed from 51.56±12.45 to 63.21±14.43 ms (p<0.05) from 59.40±13.58 to 68.33±14.55 ms (p<0.05), respectively. The changes in serum potassium and calcium levels were related with QT interval prolongation.

QT and QTc interval and dispersion increase in HD patients. Prolonged QT interval indices had relation with K(+) and Ca(++) ions before but not after HD.