ORIGINAL ARTICLE

Oral magnesium therapy, exercise heart rate, exercise tolerance, and myocardial function in coronary artery disease patients

R Pokan¹, P Hofmann², S P von Duvillard³, G Smekal¹, M Wonisch⁴, K Lettner¹, P Schmid⁵, M Shechter⁶, B Silver⁷, N Bachl¹

¹ Department of Sport and Exercise Physiology, University of Vienna, Vienna, Austria
² Department of Sports Sciences, University of Graz, Graz, Austria
³ Human Performance Laboratory, Department of Health and Human Performance, Texas A&M University-Commerce, Commerce, TX, USA
⁴ Department of Internal Medicine, University of Graz, Graz, Austria
⁵ Center for Cardiac Rehabilitation, Bad Schallerbach, Austria
⁶ The Heart Institute, Chaim Sheba Medical Center and the Tel Hashomer Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
⁷ IntraCellular Diagnostics, Inc., Foster City, CA, USA

Correspondence to:
Serge P von Duvillard
Department of Health and Human Performance, Texas A&M University-Commerce, PO Box 3011, Commerce, TX 75429-3011, USA; serge_vonduvillard{at}tamu-commerce.edu

Background: Previous studies have demonstrated that in patients with coronary artery disease (CAD) upward deflection of the heart rate (HR) performance curve can be observed and that this upward deflection and the degree of the deflection are correlated with a diminished stress dependent left ventricular function. Magnesium supplementation improves endothelial function, exercise tolerance, and exercise induced chest pain in patients with CAD.

Purpose: We studied the effects of oral magnesium therapy on exercise dependent HR as related to exercise tolerance and resting myocardial function in patients with CAD.

Methods: In a double blind controlled trial, 53 male patients with stable CAD were randomised to either oral magnesium 15 mmol twice daily (n = 28, age 61±9 years, height 171±7 cm, body weight 79±10 kg, previous myocardial infarction, n = 7) or placebo (n = 25, age 58±10 years, height 172±6 cm, body weight 79±10 kg, previous myocardial infarction, n = 6) for 6 months. Maximal oxygen uptake (VO_2max), the degree and direction of the deflection of the HR performance curve described as factor k<0 (upward deflection), and the left ventricular ejection fraction (LVEF) were the outcomes measured.

Results: Magnesium therapy for 6 months significantly increased intracellular magnesium levels (32.7±2.5 v 35.6±2.1 mEq/l, p<0.001) compared to placebo (33.1±3.1.9 v 33.8±2.0 mEq/l, NS), VO_2max (28.3±6.2 v 30.6±7.1 ml/kg/min, p<0.001; 29.3±5.4 v 29.6±5.2 ml/kg/min, NS), factor k (–0.298±0.242 v –0.208±0.260, p<0.05; –0.269±0.336 v –0.272±0.335, NS), and LVEF (58±11 v 67±10%, p<0.001; 55±11 v 54±12%, NS).

Conclusion: The present study supports the intake of oral magnesium and its favourable effects on exercise tolerance and left ventricular function during rest and exercise in stable CAD patients.

Abbreviations: ANOVA, analysis of variance; CAD, coronary artery disease; 2D, two dimensional; HR, heart rate; HRPC, heart rate performance curve; LA, blood lactate concentration; LSD, least significant differences; LTP, lactate turn point; LVDD, left ventricular internal diameter during diastole; LVEF, left ventricular ejection fraction; LVSD, left ventricular internal diameter during systole; [Mg]i, intracellular magnesium level; P_max, maximum power; SD, standard deviation

Keywords: echocardiography; exercise; heart rate performance curve; magnesium

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