SearchStroke Prevention in AF
Reducing the risk of thromboembolism with anticoagulation
Atrial fibrillation (AF) is the most common sustained form of cardiac arrhythmia. Because of improvements in the care of conditions such as myocardial infarction and heart failure, as well as the aging of the population, the prevalence of AF is increasing.4
Professor Gregory YH LipIrrespective of a rate-control or rhythm-control strategy, stroke prevention with appropriate thromboprophylaxis still remains central to the management of atrial fibrillation.
Professor of Cardiovascular Medicine at the University of Birmingham, United Kingdom Director of the Haemostasis Thrombosis and Vascular Biology Unit, University Department of Medicine at City Hospital, Birmingham
AF is associated with a markedly increased long-term risk of thromboembolism. Cardiac emboli that lodge in the cerebral circulation to cause an ischaemic stroke are a major complication of AF; approximately one in every six strokes occurs in a patient with AF.125 Anticoagulation is indicated to reduce the risk of thromboembolism in all patients with AF except in those with lone AF (those under 60 years of age with no evidence of cardiopulmonary disease) or in patients with contraindications to this therapy.22
Many patients require lifelong anticoagulation therapy
The risk of stroke in AF varies depending on cardiovascular status, coronary anatomy, and age.126 In nonvalvular AF, the stroke risk is between two and seven times as great as in people with AF; in patients with rheumatic heart disease and AF, the stroke risk is increased 17-fold.22 It is important to note that treatments intended to restore normal sinus rhythm do not necessarily reduce stroke risk in AF. Therefore, even for patients who have undergone successful cardioversion, lifelong anticoagulation is appropriate when the risk of recurrent AF is high.4
Data compiled in meta-analyses of stroke prevention in AF provide strong support for the use of vitamin K antagonists (VKAs) (ie, warfarin, adjusted to maintain the INR in the range of 2.0 to 3.0).125, 127 Pooled data from six trials, involving 2900 patients, showed that adjusted-dose warfarin decreased stroke risk by 64%, compared with a 22% decrease in risk in patients taking antiplatelet agents (eight studies, N=4876).
Balancing risks and benefits of therapy
Bleeding is the major complication associated with VKA use in stroke prevention in AF. This risk varies with age, being substantially higher in those 80 years of age or older (13.1 per 100 patient-years) compared with younger patients (4.7 per 100 patient-years).128 As in all situations involving anticoagulant use, clinicians must balance the risk of haemorrhage against the benefits of preventing thrombosis.
There is widespread underutilisation of anticoagulant therapy to prevent stroke in patients with AF. The reasons are multifactorial. Some patients refuse treatment because of the inconvenience of treatment with VKAs, which require frequent blood tests to monitor therapy and dosage adjustments, as well as food restrictions. Others may choose to forgo treatment because their fear of bleeding complications may outweigh their perception of likely benefits. Improved physician-patient communication may be required to ensure that all patients are educated adequately about the risk/benefit ratio of anticoagulation in AF.4 Novel approaches to anticoagulant therapy may one day alleviate some of the issues and challenges associated with VKA use.
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Windows Live- 4 - Lip GY, Tse HF. Management of atrial fibrillation. Lancet. 2007;370(9587):604-618.
- 125 - Hart RG, Halperin JL. Atrial fibrillation and thromboembolism: a decade of progress in stroke prevention. Ann Int Med.1999;131(9):688-695.
- 22 - Fuster V, Rydén LE, Cannom DS, et al. ACC/AHA/ESC 2006 Guidelines for the Management of Patients with Atrial Fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Circulation. 2006;114(7):e257-e354.
- 126 - Lip GY, Lim HS. Atrial fibrillation and stroke prevention. Lancet Neurol. 2007;6(11):981-993.
- 127 - Hart RG, Pearce LA, Aguilar MI. Meta-analysis: antithrombotic therapy to prevent stroke in patients who have nonvalvular atrial fibrillation. Ann Intern Med. 2007;146(12):857-867.
- 128 - Hylek EM, Evans-Molina C, Shea C, Henault LE, Regan S. Major hemorrhage and tolerability of warfarin in the first year of therapy among elderly patients with atrial fibrillation. Circulation. 2007;115(21):2689-2696.
- Arrhythmia
- Any variation from the normal rhythm of the heart beat (e.g., sinus arrhythmia, premature beat, heart block, atrial fibrillation, atrial flutter, pulsus alternans, and paroxysmal tachycardia).
- Myocardial infarction
- Destruction of heart tissue due to reduced blood flow to the heart. Also known as a heart attack. It usually results from coronary artery disease and is more severe than angina.
- Ischaemic stroke
- Potentially fatal brain damage due to interrupted blood supply to the brain caused by thrombosis or an embolism.
- Vitamin K
- An essential cofactor in the carboxylation of glutamic residues on the procoagulant forms of Factors II, VII, IX, and X. This ultimately leads to increased formation of thrombin and fibrin.
- Warfarin
- A vitamin K antagonist. Most commonly used oral anticoagulant in chronic prevention or treatment of VTE.
- International Normalised Ratio
- A system for standardising the reports of blood clotting tests and used to monitor the effects of warfarin. INR values should remain within 2.0–3.0 to ensure optimal safety and efficacy in patients with atrial fibrillation.
- Vitamin K antagonist
- Vitamin K antagonists block the regeneration of the reduced form of vitamin K.
