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New approaches to treatment of myocardial infarction
J H Chesebro1, L Badimon, V Fuster
1Mayo Clinic, Rochester, Minnesota 55905.
Insights
Maximizing myocardial salvage through timely reperfusion is key in acute myocardial infarction (AMI). Maintaining a patent infarct-related artery post-thrombolysis significantly reduces mortality, with anticoagulation playing a crucial role.
Area of Science:
- Cardiology
- Thrombosis Research
- Pharmacology
Background:
- Acute transmural infarction survival is linked to infarct size.
- Thrombolytic therapy aims to salvage myocardium by restoring infarct-related artery (IRA) patency.
- Randomized trials demonstrate reduced mortality with thrombolysis.
Purpose of the Study:
- To evaluate the role of IRA patency in reducing mortality post-myocardial infarction.
- To compare the efficacy of different thrombolytic agents.
- To investigate the mechanisms of rethrombosis and the impact of anticoagulation.
Main Methods:
- Review of randomized trials comparing thrombolytic agents (recombinant tissue-type plasminogen activator vs. streptokinase).
- Analysis of factors influencing rethrombosis, including residual thrombus, thrombin, and platelet activity.
- Evaluation of anticoagulation strategies, particularly heparin use.
Main Results:
- A patent IRA, irrespective of left ventricular function, is associated with reduced mortality.
- Recombinant tissue-type plasminogen activator is superior to streptokinase in restoring IRA flow.
- Rethrombosis is linked to residual thrombus, thrombin activity, and platelet activation.
- Heparin anticoagulation shows promise in reducing residual stenosis post-thrombolysis.
Conclusions:
- Maintaining IRA patency is critical for improving survival after acute myocardial infarction.
- Effective anticoagulation, especially with heparin, is essential for preventing rethrombosis and reducing mortality.
- Thrombin and platelet activity are key targets for optimizing thrombolytic therapy.
Abstract:
Survival of patients with acute transmural infarction is largely related to the size of the myocardial infarction. The goal of thrombolytic therapy in acute myocardial infarction is maximal salvage of myocardium by reestablishment of flow in the occluded infarct-related artery and the establishment and maintenance of a patent infarct-related artery. Results of randomized trials show a significant reduction in mortality in patients who have undergone thrombolysis. A patent infarct-related artery, even in the absence of a change in left ventricular function, is associated with reduced mortality. The Thrombolysis in Myocardial Infarction Trial and the European Cooperative Trial showed that recombinant tissue-type plasminogen activator is superior to streptokinase in reestablishing flow in a totally occluded artery. Experimental and clinical evidence suggests that thrombolysis and thrombosis occur simultaneously, and that lysis appears to increase both thrombin and platelet activity. Effective reduction of thrombosis accelerates thrombolysis. Rethrombosis after thrombolysis is due to anchored residual thrombus, which alters the hemorrheology of blood flow and produces a highly thrombogenic substrate that is largely due to residual fibrin-bound thrombin. Platelet deposition is directly related to severity of residual stenosis and shear rate. Thrombin appears to be the most potent of the 5 potential stimulators of platelet activation during arterial thrombosis. Proper anticoagulation can play an important role in reducing thrombosis. Experimental evidence strongly supports the use of heparin during and after thrombolysis. A recently reported study shows continued reduction of residual stenosis after 1 month of vigorous anticoagulation with intravenous heparin and subsequent oral anticoagulation.(ABSTRACT TRUNCATED AT 250 WORDS)