Canadian Anaesthetists’ Society Journal

, Volume 28, Issue 4, pp 329–333 | Cite as

The effect of slow releasing oral magnesium chloride on the qtc interval of the electrocardiogram during open heart surgery

  • Barry S. Krasner
  • Robert Girdwood
  • Harry Smith


Recent work in both animal and human studies emphasizes the value of magnesium in the maintenance of the functional and structural integrity of cardiac muscle. Both intracellular and extracellular magnesium concentrations can vary independently and the serum and red cell magnesium levels may not give an accurate account of intracellular cardiac magnesium deficiency. However, electrocardiographic studies of magnesium levels could provide an accurate index of intracellular cardiac magnesium levels.

Twenty-four patients scheduled electively for mitral valve replacement were studied to evaluate the effect of slow releasing oral magnesium chloride on the QTc interval of the electrocardiogram. Although pretreatment QTc values in all patients were not significantly different, there was a highly significant difference between the control group and the treatment group after four days of preoperative treatment with oral magnesium chloride. During the postoperative phase of the trial, all patients developed a similar pattern of increase in QTc interval, reaching a peak at the end of the second day and followed by a decrease over the final two days. All patients who developed arrhythmias postoperatively had not been pretreated (primed) with oral magnesium chloride and had abnormal QTc intervals both before and after operation.

The results of this study demonstrate the usefulness of oral magnesium chloride in reducing the QTc interval of the electrocardiogram and so protecting the myocardium against possible arrhythmias.

Key Words

Heart electrocardiogram QTc interval magnesium 


Des études recentes effectuées chez l’homme et chez I’animal ont souligné le rôle important du magnésium dans le maintien de l’intégrité structurelle et fonctionnelle du muscle cardiaque. Comme les concentrations intraet extra-cellulaires du magnésium peuvent varier de façon independante, les déterminations dex taux de magnésium dans les globules rouges et dans le sérum peuvent ne pas révéler des déficiences de cet ion dans la cellule myocardique. L’étude des modifications électrocardiographiques pourrait d’autre part fournir un index précis de la concentration de cet ion au niveau de la cellule myocardique.

Vingt quatre patients devant subir un remplacement valvulaire mitral ont fait l’objet d’une étude dont le but était d’évaluer l’influence d’une administration orale de chlorure de magnésium à libération lente sur la durée de l’intervalle QTc de l’électrocardiogramme. Une différence hautement significative a été observée dans la durée de l’intervalle QTcdes malades ainsi traités au chlorure de magnésium pendant quatre jours avant la chirurgie par rapport à celle trouvée chez les patients non traités. Après l’intervention, la durée de l’intervalle QTc s’est prolongée chez tous les patients, le maximum de prolongation survenant au deuxième jour post-opératoire pour ensuite se raccourcir durant les deux jours suivants. Tous les cas d’arythmie observés sont survenus chez des patients n’ayant pas reçu de chlorure de magnesium avant l’intervention et les intervalles QTc de tous ces patients étaient anormaux avant et après la chirurgie.

Les résultats de ce travail démontrent que l’administration de chlorure de magnésium se traduit au niveau de l’électrocardiogramme par un raccourcissement de l’intervalle QTc et contribue à prévenir des arythmies éventuelles.


  1. 1.
    Lehr, D., Chau, R. &Irene, S. Possible role of magnesium loss in the pathogenesis of myocardial fiber necrosis. Recent Advan. Stud. Cardiac Struct. Metabol.6: 95 (1975).Google Scholar
  2. 2.
    Fedelesova, M.,et al. Prevention by K+, MG++-Asparate of isoproterenol-induced metabolic changes in the myocardium. Recent Advan. Stud. Cardiac Struct. Metabol.6: 59 (1975).Google Scholar
  3. 3.
    Seelig, M.S. Myocardial loss of functional magnesium in cardiomyopathies of diverse etiology. Recent Advan. Stud. Cardiac Struct. Metabol.1: 626 (1972).Google Scholar
  4. 4.
    Chipperfield, B. &Chipperfield, J.R. Heart- muscle magnesium, potassium and zinc concentrations after sudden death from heart-disease, Lancet2: 293 (1973).PubMedCrossRefGoogle Scholar
  5. 5.
    Behr, G. &Burton, P. Heart-muscle magnesium. Lancet2: 450 (1973).PubMedCrossRefGoogle Scholar
  6. 6.
    Chipperfield, B., Chipperfield, J.R., Behr, G.,tal. Lancet1: 21 (1975).Google Scholar
  7. 7.
    Krasner, B.S. &Girdwood, R. The use of oral magnesium chloride (slow releasing) in open-heart surgery with special reference to arrhythmias and recovery times. Abstracts of Scientific Papers, A.S.A. Meeting, Chicago, 589–590 (1978).Google Scholar
  8. 8.
    Wallach, S. &Dimich, A. Radiomagnesium turnover studies in hypomagnesemic states. Ann. N.Y. Acad. Sci.162: 963–972 (1969).PubMedCrossRefGoogle Scholar
  9. 9.
    Aikawa, J.K. The role of magnesium in biologic processes, Springfield, 111. Charles C. Thomas (1963).Google Scholar
  10. 10.
    Lipman, B.G., Massie, E. & Kleiger, R.E. Clinical scalar electrocardiography. Year Book Medical Publishers, p. 570, (1972).Google Scholar
  11. 11.
    Krasner, Barry S. Cardiac effects of magnesium with special references to anaesthesia: a review. Canad. Anaesth. Soc. J.26: 181–185 (1979).PubMedCrossRefGoogle Scholar
  12. 12.
    Laborit, H. New physiological concepts of cardiovascular functions. Therapeutic consequences.In: Electrolytes and Cardiovascular Diseases, edited by E. Bajusz, Basel: Karger, vol.2, p. 239 (1966).Google Scholar
  13. 13.
    Nieper, H.A. &Blumberger, K. Electrolyte transport therapy of cardiovascular diseases. In: Electrolytes and Cardiovascular Diseases, edited by E. Bajusz, Basel: Karger, vol. 2, p. 141 (1966).Google Scholar
  14. 14.
    Szent-Gyorgyi, A. The ATP molecule, bioenergetics. New York, Academic Press, Inc., p. 64 (1957).Google Scholar
  15. 15.
    Polimeri, P. I. &Page, E. Magnesium in heart muscle, Circ. Res.33: 367 (1973).Google Scholar
  16. 16.
    Schamroth, L. An introductory to electrocardiography. 3rd ed., Blackwell Scientific Publications, p. 175 (1966).Google Scholar
  17. 17.
    Schwartz, P.J. Cardiac sympathetic innervations and the sudden infant death syndrome. Am. J. Med.60: 176–172 (1976).CrossRefGoogle Scholar

Copyright information

© Canadian Anesthesiologists 1981

Authors and Affiliations

  • Barry S. Krasner
    • 1
  • Robert Girdwood
    • 2
  • Harry Smith
    • 3
  1. 1.Department of AnesthesiologyLenox Hill HospitalNew YorkUSA
  2. 2.Cardiothoracic UnitBaragwanath Hospital, University of WitwatersrandJohannesburgSouth Africa
  3. 3.Department of BiostatisticsMount Sinai School of MedicineNew York

Personalised recommendations