oa Interim : Interdisciplinary Journal - Is intravenous magnesium effective in cardiac arrhythmias?
Magnesium is the second most abundant intracellular cation with many control and regulatory functions. It regulates energy production and utilization and modulates activity of membrane ionic channels. Magnesium has direct control effects on cardiac myocyte ion channels making it useful in certain arrhythmias. Calcium is responsible for pacemaker excitation and for excitation-contraction coupling in myocytes but increased intracellular calcium produces early and late afterdepolarisations initiating arrhythmias. Magnesium regulates calcium channel activity preventing raised intracellular levels. Potassium channel activity is enhanced by magnesium hyperpolarizing the cell reducing arrhythmia generation. Magnesium is effective against long QT Torsade de Pointes. In rapid atrial fibrillation magnesium produces rate control slowing AV nodal conduction. Magnesium prevents digitalis toxicity due to associated hypomagnesemia.
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