The effect of different dialysate magnesium concentrations on QTc dispersion in hemodialysis patients.
BACKGROUND
Electrolyte changes during dialysis affect corrected QT (QTc) and QTc dispersion (QTcd), a surrogate marker of arrhythmogenicity. The impact of magnesium on QTcd is not clear.


METHODS
Twenty-two stable patients on maintenance hemodialysis were enrolled in this study. Each underwent two consecutive hemodialysis sessions at least 2 days apart, the first against normal magnesium dialysate (with magnesium at 1.8 mg/dL) followed by a low magnesium dialysate (with magnesium at 0.6 mg/dL). Pre- and post-dialysis weights, blood pressure, electrolytes, and 12-lead surface EKG were recorded. The QT interval and the QTcd were calculated before and after dialysis in both sessions.


RESULTS
Of 22 patients, 16 were female. The mean age ± SD was 53.7 ± 18.0 years. The mean change of QTcd (pre- vs. post-dialysis) was 9.5 ms (p = 0.120) and 9.3 ms (p = 0.145) in low and normal magnesium groups, respectively. Using univariate analysis, there was a statistically significant decrease in the mean blood pressure, weight, potassium, magnesium, and QTc interval post-dialysis (compared to pre-dialysis) in both groups (p ≤ 0.049). Post-dialysis concentrations of sodium and calcium were unchanged (compared to pre-dialysis) but bicarbonate increased with both dialysate groups (p < 0.001). The mean change of QTcd was not significant pre- versus post-dialysis by univariate analysis in either group. Multiple linear regression analysis adjusting for pertinent factors did not change the results in either of the two groups.


CONCLUSIONS
Using a low magnesium dialysate bath in hemodynamically stable hemodialysis patients without preexisting advanced cardiac disease does not significantly impact QTcd.
Division of Nephrology, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI, USA.
Farsad
F
Afshinnia
Hardik
H
Doshi
Panduranga S
PS
Rao
D001145:Arrhythmias, Cardiac / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*; D018592:Cross-Over Studies; D015314:Dialysis Solutions / Q000737:chemistry*; D004562:Electrocardiography / Q000187:drug effects*; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000150:complications / Q000378:metabolism / Q000628:therapy*; D008274:Magnesium / Q000032:analysis* / Q000493:pharmacokinetics; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis; D012189:Retrospective Studies
D015314:Dialysis Solutions; D008274:Magnesium