11 The Use of Antithrombotic Drugs in Artery Disease

Abstract

Evaluating the use of antithrombotic drugs in artery disease has been a long and difficult process, which is far from complete. The aims of treatment have ranged from the primary prevention of myocardial infarction or stroke, through the restoration of blood flow to ischaemic organs in order to salvage threatened tissue, to the prevention of recurrent vascular occlusion. Drugs studied in depth by clinical trial include the oral anticoagulants, antiplatelet drugs (especially aspirin), and thrombolytic agents. Their results are considered under the headings of coronary artery disease, cerebral ischaemia, and peripheral vascular disease. Aspirin, with or without dipyridamole, prevents progression of unstable angina to myocardial infarction or death, probably reduces long-term mortality after myocardial infarction, and prevents aortocoronary bypass graft occlusion. It decreases the risks of stroke or death in patients with transient cerebral ischaemia, diminishes cardiovascular morbidity after a thrombotic stroke, and may improve the outcome after some kinds of surgery for peripheral vascular disease. The benefits of oral anticoagulant treatment to prevent artery occlusion remain poorly defined. Oral anticoagulants prevent systemic embolism in many groups of high-risk patients, and probably reduce the risk of recurrence after embolism has occurred. Whether their long-term use to prevent reinfarction in patients with a previous myocardial infarct can be justified remains uncertain. They are of little or no proven value in patients with transient cerebral ischaemia or thrombotic stroke. On the other hand, there is increasing support for early thrombolytic treatment after myocardial infarction, especially since two multicentre trials have now shown reduced mortality in patients treated with intracoronary streptokinase within 4-6 hours of infarction and a further large multicentre study also demonstrated reduced mortality in patients treated with early intravenous streptokinase. In addition, the local infusion of streptokinase leads to recanalization in a high proportion of patients with a recent peripheral artery occlusion who are poor candidates for surgery.