Cell-associated magnesium and QT dispersion in hemodialysis patients.
BACKGROUND
Impaired magnesium (Mg) homeostasis has been implicated in a variety of cardiovascular disturbances, including ventricular arrhythmias and changes in the interval between the onset of wave Q to the end of wave T (QT interval) on electrocardiogram. Cardiac arrhythmias are common in patients on hemodialysis therapy.


METHODS
We investigated the relationship between QT interval corrected for heart rate (QTc) dispersion and Mg content in peripheral blood mononuclear cells (PBMC) of chronic hemodialysis patients treated with high-dose calcium carbonate providing Mg in excess (group I; n = 18) or low-dose calcium carbonate and smaller Mg load (group II; n = 13).


RESULTS
Mean Mg content in PBMC of group I patients (27.9 +/- 4.2 [SD] micromol/L/mg protein) was significantly greater than in group II patients (10.4 +/- 4.1 micromol/L/mg protein; P < 0.05) and greater in both groups than in healthy control subjects (2.75 +/- 0.6 micromol/L/mg protein; P < 0.05). Mean QTc dispersion was significantly longer (74.6 +/- 21.4 milliseconds) in group I than group II (37.8 +/- 13.1 milliseconds; P < 0.02) and longer in both groups than in controls (27.3 +/- 9.6 milliseconds; P < 0.05). After dialysis, in both groups of patients, cell-associated Mg (c-a Mg) levels and QTc dispersion were significantly greater (P < 0.05) than before dialysis started. One week after stopping calcium carbonate treatment, group 1 patients showed significant reductions in predialytic c-a Mg levels (to 19.5 +/- 9.8 micromol/L/mg protein; P < 0.05) and QTc dispersions (to 48.9 +/- 23.7 milliseconds; P < 0.05). Plasma Mg and other electrolyte concentrations prior to and during hemodialysis did not correlate with QTc dispersion.


CONCLUSIONS
Prolongation of QTc dispersion in patients on chronic hemodialysis therapy could be, at least in part, a consequence of increased concentrations of c-a Mg resulting from excess daily Mg intake.
Averbukh
Zhan
Z
Nephrology Division and Department of Medicine F, Assaf Harofeh Medical Center, Zerifin, Israel. aberbukhzh@asaf.health.gov.il
Rosenberg
Rosa
R
Galperin
Elena
E
Berman
Sylvia
S
Cohn
Mirel
M
Cohen
Nathan
N
Modai
David
D
Efrati
Shai
S
Weissgarten
Joshua
J
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001774:Blood Chemical Analysis / Q000379:methods; D002119:Calcium Carbonate / Q000009:adverse effects / Q000494:pharmacology; D015331:Cohort Studies; D004334:Drug Administration Schedule; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007674:Kidney Diseases / Q000097:blood / Q000628:therapy; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism*; D008133:Long QT Syndrome / Q000097:blood* / Q000139:chemically induced / Q000503:physiopathology; D008274:Magnesium / Q000097:blood* / Q000494:pharmacology / Q000502:physiology; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis / Q000009:adverse effects* / Q000379:methods; D013607:Tablets
D013607:Tablets; D002119:Calcium Carbonate; D008274:Magnesium