In the setting of acute myocardial infarction, when increased serum magnesium might be beneficial, there is actually a decline in free magnesium. This comes about because of a sharp rise in free fatty acids brought about by catecholamine induced lipolysis at the onset of chest pain, that results in a completing of magnesium in the form of insoluble soaps. Thus, although total body magnesium does not decrease, magnesium available in a free form that is capable of exerting a cardioprotective effect declines. Hence, there is a strong theoretical rationale for supplemental magnesium administration in this setting.