Oral magnesium therapy improves endothelial function in patients with coronary artery disease

Background-Magnesium blocks many of the physiological actions of calcium. N evertheless, the impact of magnesium supplementation on endothelial functio n and exercise tolerance in stable coronary artery disease (CAD) patients h as not been assessed. Methods and Results-In a randomized, double-blind, placebo-controlled trial , 50 stable CAD patients (41 men and 9 women, mean +/- SD age 67 +/- 11 yea rs, age range 42 to 82 years) were randomized to receive either magnesium ( n=25) (30 mmol/d Magnosolv-Granulat; Asta Medica Company, Inc) or placebo ( n=25) for 6 months. Before and after 6 months, endothelium-dependent brachi al artery flow-mediated vasodilation (FMD) and endothelium-independent NTG- mediated vasodilation were assessed with high-resolution (10-MHz) ultrasoun d. Exercise stress testing was performed with use of the Bruce protocol. In tracellular magnesium concentrations ([Mg2+](i)) were assessed from subling al cells through x-ray dispersion (EXA) (normal mean +/- SD values 37.9 +/- 4.0 mEq/L). The magnesium therapy significantly increased postintervention ([Mg2+](i) versus placebo (36.2 +/- 5.0 versus 32.7 +/- 2.7 mEq/L, P < 0.0 2). There was a significant correlation in the total population between bas eline [Mg2+](i) and baseline FMD (r = 0.48, P < 0.01). The magnesium interv ention resulted in a significant improvement in postintervention FMD (15.5 +/- 12.0%, P=0.02 compared with baseline), which was not evident with place bo (4.4 +/- 2.5%, P=0.78 compared with baseline). There was better exercise tolerance (9.3 +/- 2.0 versus 7.3 +/- 3.1 minutes, P=0.05) and less ischem ic ST-segment changes (4 versus 10 patients, P=0.05) in the magnesium versu s placebo groups, respectively. Conclusions-Oral magnesium therapy in CAD patients is associated with signi ficant improvement in brachial artery endothelial function and exercise tol erance, suggesting a potential mechanism by which magnesium could beneficia lly alter outcomes in CAD patients.