Failed thrombolysis in myocardial infarction

Optimizing the use of thrombolytics in ST-segment elevation myocardial infarction

The advent of thrombolytic therapy was a major advance in the treatment of ST-segment elevation myocardial infarction (STEMI). The administration of fibrinolytic reperfusion therapy can reduce mortality rates by as much as 30%, with the greatest benefit observed if therapy is administered soon after symptom onset. Outcomes with thrombolytic therapy are improved if there is adjunctive treatment with aspirin, clopidogrel and an anti-thrombin agent. Although there is evidence that primary percutaneous coronary intervention (PCI) is the most effective reperfusion strategy, the majority of hospitals still do not have PCI capabilities and, thus, thrombolytic therapy remains a cornerstone of treatment for STEMI. Trials of thrombolytic therapy have demonstrated that initial patency rates can approach 85%, but there is still a need for improvement of non-invasive markers that predict failure or re-occlusion of the infarct-related artery. Because of the overwhelming data demonstrating the importance of rapid reperfusion, current studies are examining the role of earlier treatment of patients with STEMI via pre-hospital administration and/or coordinated systems for rapid diagnosis, transfer and delivery of definitive care. Facilitated PCI, a strategy of thrombolytic therapy followed by immediate PCI, has not been shown to be beneficial and current studies are examining the optimal timing of coronary angiography after thrombolytic therapy.

Glycoprotein IIb/IIIa antagonists in the setting of rescue percutaneous coronary intervention

It is clear that survival and better outcomes after acute myocardial infarction (AMI) are dependent on rapid, complete, and sustained reperfusion of the affected myocardium. Thrombolytic therapy is currently the most common reperfusion strategy in AMI, however, a significant proportion of patients fail to reach reperfusion with this form of therapy. There is evidence from randomized trials that rescue percutaneous coronary intervention (PCI) for failed thrombolysis may convey better outcomes to patients when compared to a conservative management. Nevertheless, it is not surprising that in this inherently thrombogenic milieu, rescue PCI has a lower success rate and a high incidence of rethrombosis, which have a profoundly negative impact on the outcome of patients. Platelets are thought to play a central role in the pathophysiology of failed thrombolysis and in the thrombotic complications following PCIs. Therefore, platelet glycoprotein (GP) IIb/IIIa antagonist may be of benefit in the setting of rescue PCI. Two retrospective subgroup analyses have suggested that these potent antiplatelet agents may improve the outcome of patients undergoing rescue PCI after failed full-dose thrombolytic therapy. An increase in major bleeding, however, has also been noted. Therefore, in light of the lack of evidence deriving from randomized, placebo-controlled trials, careful consideration of several aspects relevant to this setting is needed before GP IIb/IIIa antagonists are administered in rescue percutaneous coronary procedures.