Current theories and therapies relating to acute myocardial infarction and reperfusion injury.

Acute myocardial infarction (AMI) was previously treated with conservative strategies that allowed the process of ischaemia to proceed uninterrupted. The resultant myocardial necrosis and reduced ventricular function were accepted outcomes. The emergence of thrombolytic agents such as streptokinase and tissue plasminogen activator (tPA) revolutionised the management of coronary artery occlusion, yet the spectre of further myocardial necrosis and ventricular dysfunction remains. The concept of 'reperfusion injury', an acute process described as occurring after thrombolysis of a coronary artery occlusion and referring to an unexpected loss of ventricular function, has been extensively researched. Current research papers describing the mechanisms involved appear either to emphasise those processes that occur within the actual myocytes, or those events within the coronary vasculature. In most papers however, oxygen free radicals (OFRs) are accepted as mediators of cellular injury; despite the debate surrounding their primary source. Efforts to minimise the effects of primary ischaemia and subsequent 'reperfusion injury', appear to be focused upon restoring cardioprotection against the increased levels of these damaging molecules. Scavenging agents such as N-acetylcysteine (NAC) which can also assist in dilating coronary vessels as well as preventing further platelet aggregation, when combined with glyceryl trinitrate (GTN), are being closely scrutinised. Despite the advances made, the processes within the myocardium remain somewhat a mystery and the search continues for more effective strategies to ensure myocardial viability and long-term function. Critical care nurses need not only to be aware of the aim of these new strategies, but should also be conscious of their effect on the patients receiving them.