A review of the long term effects of thrombolytic agents

Unequivocal evidence exists that reperfusion therapy, when given within 12 hours after onset of symptoms, saves the lives of patients with acute myoca rdial infarction (MI), As a result, the routine use of such treatment has i ncreased rapidly since the mid-1980s but the rates of utilisation have been relatively static over the last decade at approximately 50% of patients wi th acute MI. The major question arising in this respect is: is the benefit of reperfusion therapy, which is achieved during the acute phase in evolvin g MI, maintained on the long term? The main thrombolytic agents currently in use are streptokinase, alteplase, anistreplase, urokinase and reteplase, Other studies compared coronary ang ioplasty with thrombolytic therapy and investigated the effect of an additi onal angioplasty procedure after failed thrombolytic therapy, Furthermore, several studies have been performed to investigate the effect of initiation of reperfusion therapy before hospital admission. It is generally agreed that, in particular, patients receiving early treatm ent within 6 hours from onset of symptoms and patients with ST elevation be nefit most from thrombolytic therapy. One would theoretically expect that i nfarct size reduction achieved by reperfusion therapy would also have a ben eficial effect on the survival, not only during the hospital stay but also afterwards, resulting in diverging survival curves between patients who rec eived reperfusion therapy and those who did not. However, the survival curv es run perfectly parallel after hospital discharge from 1 year up to year 1 0 in most studies. The explanation for a lack of extra benefit may be a net result of combining the results of several subgroups, For example, thrombo lytic therapy results in more frequent reinfarction especially in the first year, or patients with low left ventricular ejection fraction could surviv e the hospital phase because of effective thrombolytic therapy, but they su rvive at high risk. Although several trials suggest that primary percutaneous transluminal coro nary angioplasty may be more beneficial than thrombolytic therapy in acute MI, these data should be interpreted cautiously unless confirmed by larger studies with long term results. In addition, evidence exists to suggest tha t administration of fibrinolytic treatment, under certain conditions, befor e hospital admission may lead to further improvement of a patient's prognos is. Again, further investigation is warranted. The conclusion is that clear evidence exists that the early improved surviv al after thrombolytic therapy has been shown to be maintained beyond a deca de. However, the expected theorectical additional benefit of reperfusion th erapy after hospital discharge has not been observed.