engleski

Antikoagulant therapy in the prevention and treatment of stroke

Anticoagulant agents that are used in practice for years, have been the subject of many discussions. In 80% of stroke cases, the underlying causes are ischemic events due to vascular occlusion.Antithrombotic therapy primarily refers to ischemic stroke, however, the risk of intracranial hemorrhage is the main hindrance to the use ot antithrombotic drugs in both the prevention and treatment of stroke. Antithrombotic therapy has the crucial role in the prevention of ischemic stroke. The highest risk is associated with the use of thrombolytics. The risk is less pronounced with anticoagulants, and is the least although still present with antiplatelet agents. The treatment of vascular risk factors such as hypertension, cigarette smoking, diabetes mellitus and hyperlipidemia, and the use of antithrombotic agents are the two main approaches in the prevention of primary and secondary stroke. In the use of antithrombotic therapy for prevention of stroke, the absence of cardiogenic embolism should be differentiated from cardioembolic stroke. In primary prevention in noncardiogenic embolism, aspirin is the first choice drug, as it is the only drug that has been studied in primary prevention. The use of aspirin has proved reasonable in patients with atheromas (asymptomatic carotid stenosis) who are at a higher risk of myocardial infarction and cardiac death than of brain infarction. Secondary prevention primarily includes patients who have suffered first ever transient ischemic attack (TIA) or stroke and are at a high risk of any vascular event, mostly second stroke or myocardial infarction. Many questions remain open in the field, e.g., optimal aspirin doses, choice of the most appropriate antithrombotic drugs in use are ticlopidin, clopidogrel and dipyridamole. Until more data on the efficacy and safety of anticoagulants become available, antiplatetet drugs remain the drugs of choice in the prevention of atherothrombotic stroke and in patients without the cardiac origin of embolism. The prevention of cardioembolic stroke is primarily based on the specific treatment of cardiac disease and administration of oral anticoagulants. This refers to all high risk origins of cardiac ambolism (mitral stenosis, mechanical artificial valves, recent myocardial infarction, mural thrombosis of the left ventricle, atrial fibrillation.) Atrial fibrillation is the most commom origin of cardiac ambolism and is responsible for some 50% of all cardiac emboli. In atrial fibrillation, oral anticoagulants are the drugs of choice. Studies have shown that aspirin and oral anticoagulants are efficacious in the primary and secondary stroke prevention in patients with atrial fibrillation, however, oral anticoagulants are associated with a higher risk of hemorrhage. On prescribing the drug, assessment of the risk of embolic stroke and of massive hemorrhage should always be individualized. In other cardiac diseases, the antithrombotic strategy of stroke prevention is based on the principle of balancing the risk and embolism. The decision on the administration of antithrombotic therapy should be made individually for each case, weighing the risk of early occurrence of new emboli and of intracerebral hemorrhage, which mostly depends on the size of infarct. In the antithrombotic treatment of acute ischemic stroke, antithrombotic drugs, anticoagulants, thrombolytics and fibrinogen reducing agents have been used. In contrast to prevention, where an international consensus has been achieved, considerable differences related to antithrombotic strategy exist in the management of acute ischemic stroke. Numerous studies have shown that aspirin is the only antiplatelet drug that has been evaluated in the treatment of acute stroke. Of the new antiplatelet agents for the treatment of acute ischemic stroke that are currently under study, mention should be made of the GP IIb/III a receptor antagonists. Concerning atnicoagulants, various heparins have been used, e.g., nonfractionated heparin, low molecular weight heparin (LMWH), and heparinoid (Organon). It has been shown that low doses of low molecular heparin should be used in patients with hemiplegia and limited mobility for prevention of deep venous thrombosis and pulmonary embolism. Thrombolysis has brought revolution in the management of stroke, because it has demonstrated that the major goal of recovery is the fastest possible restitution of blood flow. Streptokinase, intravenous recombinat tissue plasminogen activator (IV rt-PA), and intra-arterial prourokinase are being used. Intraarterial prourokinase (IA) is an alternative to intravenous thrombolysis, however, cerebral angiogram is required to identify the site of occlusion and to allow for the agent to reach the clot. Recently, Ancrod, a viper venom protease, a fibrinogen degrading agent, has also been investigated. The antithrombotic strategy in the management of acute ischemic stroke differs according to rt-PA availability. In the countries where rt-PA has not been approved, of after 3 hours of stroke onset, aspirin in combination with low doses of LMWH is the therapy of choice in case of hemiplegia or limited mobility (for the prevention of deep venous thrombosis and pulmonary embolism).

anticoagulant; cardiogenic emoblism; transient ischemic attack

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