Dialysate bath and QTc interval in patients on chronic maintenance hemodialysis: pilot study of single dialysis effects.

INTRODUCTION: Serum concentrations of potassium (K) and calcium (Ca) influence ionic currents and play an important role in the duration of ventricular action potential. Further, the influence of alkalosis in reducing ionized calcium has been well known for a long time. The aim of this study was to assess the effects of different dialysate electrolytes and bicarbonate concentrations on changes of QTc interval in patients on chronic hemodialysis. METHODS: The study hemodialysis sessions were performed in 22 patients, with different electrolyte and bicarbonate concentrations in dialysate. Tested dialysate concentrations were K of 2 and 3 mmol/L; Ca 1.25, 1.5 and 1.75 mmol/L; and bicarbonate 30 and 34 mmol/L. An electrocardiogram (ECG) was recorded 1 hour before, at the end and every hour for 4 hours after each study dialysis session. QTc interval was measured from the beginning of the QRS complex to the end of a T wave on a 12-lead ECG. Blood was collected and K, total Ca, ionic Ca and pH evaluated. RESULTS: At the end of the study hemodialysis session with dialysate containing low K (2 mmol/L), low Ca (1.25 mmol/L) and high bicarbonate concentration (34 mmol), mean QTc interval was significantly prolonged compared with that recorded with dialysate containing high K (3 mmol/L), high Ca (1.75 mmol/L) and bicarbonate (30 mmol) (40 ± 10 milliseconds vs. 2 ± 2 milliseconds; p<0.01). Dialysate with low concentration of low Ca, K and high concentration of bicarbonate was an independent predictor of QTc; the combination of low Ca and K and high bicarbonate strongly increased the risk of prolonged QTc interval. CONCLUSION: The present pilot study shows that changes in QTc interval during hemodialysis depend on both electrolyte and bicarbonate concentrations in dialysate.

Cardiac vascular calcification and QT interval in ESRD patients: is there a link?

We will present our experience and our preliminary data about the correlation between cardiac calcification and QT interval (and QT dispersion) in uraemia. We studied 32 haemodialysis (HD) patients (age 69 +/- 16 years, time on dialysis 32 +/- 27 months) and 12 chronic kidney disease stage 4 (CKD-4) patients (age 66 +/- 17 years, uraemia duration 38 +/- 16 months). The patients were characterized by a good mineral control, as shown by serum phosphate levels (3.6 +/- 1.3 mg/dl in CKD-4 and 4.3 +/- 1.6 mg/dl in HD patients) and Ca x P product (46 +/- 17 and 49 +/- 16 mg(2)/dl(2), respectively). The parathyroid hormone levels were higher in HD than CKD-4 patients (p < 0.0001). A TC score >400 was found to be highly prevalent in both groups. Significantly more HD patients (62.5%) showed cardiac calcification than CKD-4 patients (33%; p = 0.01). The patients were matched for TC scores higher or lower than 400. The two groups differed by gender (p < 0.05), age (p = 0.026), frequency of diabetes mellitus (p < 0.01), uraemia follow-up period (p < 0.001), low-density lipoprotein cholesterol level (p = 0.009), Ca x P product (p = 0.002), parathyroid hormone level (p < 0.0001), and corrected QT dispersion (p < 0.0001). The QT interval was higher in HD and CKD-4 patients with higher TC scores (approximately 11%), but QT interval dispersion was significantly higher in patients with TC scores >400. QT dispersion showed a linear correlation with TC scores in both groups (r = 0.899 and p < 0.0001 and r = 0.901 and p < 0.0001). Male gender, age, time (months) of uraemia, low-density lipoprotein cholesterol, albumin, calcium x phosphorus product, parathyroid hormone, and TC score are important determinants of QT dispersion. Our data show that it is possible to link dysrhythmias and cardiac calcification in uraemic patients.