ANTIOXIDANT THERAPY IN REPERFUSION-INDUCE D MYOCARDIAL-ISCHEMIA

Perfusion-induced myocardial ischaemia is observed in several situatio ns : chronic coronary insufficiency, unstable angina, myocardial infar ctin, and during coronary angioplasty or bypass surgery. Oxygen-derive d free radicals are liberated in large quantities during myocardial re perfusion ischaemia. Though very toxic in experimental studies, the re sponsibility of these free radicals in myocardial injury remains to be demonstrated clinically. Oxidant stress, characterised by an imbalanc e between the free radical attack and insufficient cellular defense se ems partially responsible for reprfusion arrhythmias and post-ischemic stunning. On the other hand, its role is less evident in prolonged my ocardial ischaemia causing irreversible myocardial lesions such as inf arction. Antioxidant therapy is under evaluation in clinical trials. T here are several options : some prevent the formation of fire radicals by inhibiting the biochemical reactions which may produce them or by limiting die intervention of the neutrophils - the '' fulcrum '' of fr ee radicals formations. Other antioxidant therapies inactivate free ra dicals as they are formed by promoting their degradation or their neut ralisation. Experimental data is profuse and discordant. The models ar e very different. The first clinical trials are under way using either specific antioxidant molecules or molecules having other beneficial e ffects : in the latter case, the benefit of the antioxidant action is more difficult to demonstrate. Antioxidant therapy could play a role i n surgical myocardial protection, especially of transplant organs, in very early forms of ischaemia. It could also prevent the pejorative he modynamic consequences of myocardial stunning of the border zones of i nfarction, so enabling patients to survive a difficult period. The res ults of on-going studies should clarify the role of antioxidant therap y in reperfusion-induced myocardial ischaemia.