MYOCARDIAL-INFARCTION AND REVASCULARIZATION - CURRENT INDICATIONS

The physiopathologic role of thrombosis in the genesis of myocardial infarction, began to be suspected early in the 20th century but its logical treatment, thrombolysis was first used an a large scale only ten years ago. Today, it is well established that short, middle and long-term mortality is correlated to coronary permeability the delay in the revascularization treatment start-up, its efficacy its swiftness of action, and to the maintaining of permeability following reperfusion. The importance of rime elapse before reperfusion is obtained was demonstrated as early as 1986 by the GISSI study. According to this study the administration of streptokinase (compared to a conventional treatment) reduced mortality at 21 day respectively by 47%, 23%, and 17%, depending on whether patients were treated within one hour, three hours, or between 3 and 6 hours following the onset of the painfull symptoms. One of the major teachings of the GUSTO study, reported at the end of 1993, was the confirmation of the so-called << open artery >> theory: mortality at 30 days was of 4.5% among patients whose coronary circulation was restored at the 90th minute, whatever thrombolytic treatment was used, compared to 8.9% when the coronary artery remained occluded. The value of aspirin in preserving coronary permeability following thrombolysis was demonstrated by the ISIS-2 study : mortality at 5 weeks was reduced by 23% in the group of patients randomised to receive only aspirin, while it was reduced by 25% in the group of patients randomised to be treated with streptokinase, and by 42% in the group randomised to receive both aspirin and streptokinase, compared to the group who received neither aspirin nor streptokinase. However, mortality during the first days following randomisation was identical among the groups, with or without aspirin, which suggested its action was rather one of prevention against reocclusion than one of accelerating dissolution of the thrombus. However, in spite of improved therapeutical protocols, a normal flow, which is the major criteria for a reduced mortality, is only obtained at the 90th minute in 54% of the patients who were administered the up-to-date treatment ie aspirin-accelerated t-PA-heparin in combination. Certain measures could increase the efficacy of thrombolysis: a shorter delay in performing thrombolysis conditioned in part of a reinforcement of the health professionals' conviction that thrombolysis is valuable and allows a prompt coronary revascularization and a significant reduction of mortality; a clear definition of the best thrombolytic approach for ech individual patient: patients seen in the first 6 hours (or within the first 12 hours in case of anterior or of extended myocardial infarction) and who have no specific contra-indication, should immediately be given aspirin (160 to 325 mg) and undergo intravenous thrombolytic treatment. Intravenous heparin must also be given in case of utilisation of t-PA but the benefit of heparinotherapy seems lesser when anistreplase or streptokinase are associated to aspirin. The administration of accelerated t-PA is preferable to streptokinase in the majority of the cases, but is particularly indicated among patients aged under 75 years who have an anterior myocardial infarction or present an extended infarction, who could be treated within the first 4 hours following the onset of symptoms. The administration of accelerated t-PA should also be used among patients having a previous streptokinase or anistreplase treatment due to antibodies that may develop following a first exposition. Finally patients with a contra-indication to a thrombolytic treatment, or with a serious hemodynamic impairment, should benefit from a quickly percutaneous transluminal angioplasty.