Role of magnesium in cardiac disease.

Some aspects of the pathogenesis of cardiac disease are reviewed in the light of current knowledge of the physiological and biochemical actions of magnesium (Mg2+) on heart function. Several authors have reported a reduction of the human myocardial Mg2+ content in areas with (Mg2+ poor) soft water, without a significant alteration of Mg2+ in serum or skeletal muscle. In human during myocardial infarction, there is a reduction of Mg2+ content even in noninfarcted areas of the myocardium, followed by a transient reduction of serum Mg2+ concentration. These effects are explained by the action of catecholamines on the myocardial cells, resulting in a loss of Mg2+ accompanied by a catecholamine-induced urinary Mg2+ loss and/or increased lipolysis which binds Mg2+ as Mg2+ soaps in the adipocytes. As a consequence serum Mg2+ may be decreased. A reduced serum Mg2+ concentration may enhance the action of catecholamines on the heart muscle as well as the action of vasopressive hormones, thus provoking contraction of coronary artery smooth muscle cells and favouring the development of arrhythmia.