Mechanisms of in vitro cardioprotective action of magnesium on the aging myocardium.

Studies examining the effects of aging on the myocardium have indicated that with advancing age there are anatomical, mechanical, ultrastructural, and biochemical alterations which compromise the adaptive response of the heart and make the senescent myocardium less tolerant to surgically-induced ischemia. With the increased incidence of elderly patients as candidates for complex cardiac surgery, the investigation into methods which will increase survivability and enhance myocardial protection are of paramount importance. Previous reports have indicated that surgically-induced global ischemia is associated with alteration in cytosolic calcium accumulation ([Ca2+]i), and that the level of post-ischemic functional recovery can be correlated with control of [Ca2+]i Cardioplegia (high potassium arrest) partially ameliorates the adverse effects associated with global ischemia however; the use of magnesium (magnesium supplemented potassium icardioplegia) has been shown to provide superior myocardial protection during global ischemia and to allow for enhanced post-ischemic functional recovery. The cardioprotective mechanisms of magnesium supplemented potassium cardioplegia which allow for decreased morbidity and mortality in the cardiac surgical patient has been shown to act at the level of the sarcolemma, mitochondria and the nucleus. and may be associated with myocardial gene expression in the aged heart. In this report these mechanisms are reviewed.