Noninvasive Measurement of Tissue Magnesium and Correlation With Cardiac Levels

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Abstract
Background Intracellular magnesium ([Mg]i) plays an important role in the regulation of myocardial metabolism, contractility, and the maintenance of transsarcolemmal and intracellular ionic gradients. An understanding of the role of magnesium in the clinical setting, however, is hampered by the lack of an assay of intracellular tissue magnesium levels. Methods and Results We used energy-dispersive x-ray analysis to measure [Mg]i in sublingual epithelial cells and to correlate the level with those in atrial biopsy specimens from the same patients during cardiopulmonary bypass. Levels were also measured in acute myocardial infarction (AMI) patients before and after intravenous magnesium sulfate administration and compared with those from intensive care unit (ICU) patients and healthy individuals. A strong correlation between sublingual epithelial cell (mean, 32.1±0.3 mEq/L) and atrial tissue (mean, 32.1±0.3 mEq/L) [Mg]i was present in 18 cardiac surgery patients (r=.68, P<.002). Epithelial and atrial [Mg]i ...