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

Rochus Pokan ¹, Peter Hofmann ², Serge P von Duvillard ^3*, Gerhard Smekal ¹, Manfred Wonisch ⁴, Karin Lettner ¹, Peter Schmid ⁵, Michael Shechter ⁶, Burton Silver ⁷ and Norbert Bachl ¹

¹ University of Vienna, Austria
² Karl-Franzens-University Graz, Austria
³ Texas A&M University-Commerce, United States
⁴ Medical University Graz, Austria
⁵ Cardiac Rehabilitation Center-Bad Schallerbach, Austria
⁶ The Heart Institute-Chaim Sheba Medical Center, Israel
⁷ IntraCellular Diagnistics, Inc., United States

^* To whom correspondence should be addressed. E-mail: skyblue{at}myenet.com.

Accepted 13 June 2006

Abstract

Previous studies have demonstrated that in patients with coronary artery disease (CAD) an upward deflection of the heart rate (HR) performance curve can be observed and that this upward deflection and the degree of the deflection is correlated with a diminished stress-dependent left ventricular function. Magnesium (Mg) supplementation improves endothelial function, exercise tolerance, and exercise-induced chest pain in patients with CAD. Purpose: We studied the effects of oral Mg 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 randomized to either oral Mg 15 mmol twice daily (N = 28, age = 61¡&Oacute9 yrs, height = 171¡&Oacute7, body weight = 79¡&Oacute10 kg, previous myocardial infarction (MI), N = 7) or placebo (N = 25, age = 58¡&Oacute10 yrs, height = 172¡&Oacute6, body weight = 79¡&Oacute10 kg, previous MI, N = 6) for 6 months. Maximal oxygen uptake (VO2max), 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: Six-month Mg therapy significantly increased intracellular Mg levels (32.7¡&Oacute2.5 vs. 35.6¡&Oacute2.1 mEq/L, p<0.001) compared to placebo (33.1¡&Oacute3.1.9 vs. 33.8¡&Oacute 2.0 mEq/L, n.s.), VO2max (28.3¡&Oacute6.2 vs. 30.6¡&Oacute7.1 ml/kg/min, p<0.001; 29.3¡&Oacute5.4 vs. 29.6¡&Oacute5.2 ml/kg/min, n.s.), factor k (-0.298¡&Oacute0.242 vs. -0.208¡&Oacute0.260, p<0.05; -0.269 ¡&Oacute0.336 vs. -0.272¡&Oacute0.335, n.s.), LVEF (58¡&Oacute11 vs. 67¡&Oacute10 %, p<0.001; 55¡&Oacute11 vs. 54¡&Oacute12 %, n.s.). Conclusion: The present study supports the intake of oral Mg and its favorable effects on exercise tolerance and left ventricular function during rest and exercise in stable CAD patients.

Key Words: echocardiography, exercise, heart rate performance curve, magnesium

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