Oral anticoagulation – how intense and for how long?
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Abstract.Patients with mechanical heart valve prostheses require life‐long anticoagulation and the intensity is optimal at an International Normalized Ratio (INR) of 3.0–4.0. Individual deviations from this range should be based on the type of prosthesis, the position of the prosthesis and the risk of haemorrhage. Efforts should be made to quickly correct excessive anticoagulation and to keep the treatment within the targeted range during the largest possible fraction of the time.In nonvalvular atrial fibrillation there is a greater reduction of the risk of thromboembolic complications with the use of warfarin compared to aspirin. The intensity should be equal to INR 2.0–3.0, since lower intensities are not sufficiently effective, even in combination with aspirin. Aspirin is still preferred for patients younger than 65 years without additional risk factor.Oral anticoagulation gives a significant long‐term reduction of recurrent myocardial infarction and of total stroke after myocardial infarction. The optimal intensity is between INR 2.0 and 4.0. Running trials will determine if aspirin and warfarin yield comparable results.Patients with peripheral arterial disease, who undergo reconstructive surgery, seem to benefit from long‐term postoperative oral anticoagulation, which improves limb salvage, prolongs the patency of the vein bypass and survival of the patient. There is a need of trials addressing the intensity of anticoagulation and comparing oral anticoagulation with aspirin in this field.For venous thromboembolism 6 weeks of oral anticoagulation is sufficient for patients with calf vein thrombosis and a temporary risk factor. Proximal deep vein thrombosis, pulmonary embolism and/or unknown or permanent risk factor for thrombosis require longer treatment durations, ideally around 6 months. The prophylaxis should be targeted at an INR of 2.0–2.85, which is effective and minimizes the risk of haemorrhage. Certain biochemical thrombogenic factors will necessitate prolonged full anticoagulation.Efforts are being made to improve the safety of anticoagulant therapy through better organization of the monitoring, education of the patients, investigations of the various risks for complications as well as the development of new agents with less interactions and more selective and reproducible effects.
