Stroke Prevention in Atrial Fibrillation – Risks
Atrial fibrillation is associated with an increased risk of stroke
(AF) is the most common sustained form of cardiac arrhythmia. Because of improvements in the care of conditions such as myocardial infarction (MI) and heart failure, as well as the aging of the population, the prevalence of 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 1 in every 6 strokes occurs in a patient with AF
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.54
Many patients require lifelong anticoagulation therapy
The risk of stroke in AF
varies depending on cardiovascular status, coronary anatomy, and age.55
In non-valvular AF
, the stroke risk is between 2 and 7 times as high as in people with AF; in patients with rheumatic heart disease and AF
, the stroke risk is increased 17-fold.54
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
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).53, 56
Pooled data from 6 trials, involving 2,900 patients, showed that adjusted-dose warfarin decreased stroke risk by 64%, compared with a 22% decrease in risk in patients taking antiplatelet agents (8 studies, N=4,876).
- 36 - Lip GY, Tse HF. Management of atrial fibrillation. Lancet. 2007;370(9587):604-618.
- 53 - Hart RG, Halperin JL. Atrial fibrillation and thromboembolism: a decade of progress in stroke prevention. Ann Intern Med. 1999;131(9):688-695.
- 54 - 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.
- 55 - Lip GY, Lim HS. Atrial fibrillation and stroke prevention. Lancet Neurol. 2007;6(11):981-993.
- 56 - 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.
- Atrial fibrillation
- A heart rhythm disorder where chambers in the upper heart (atria) beat more rapidly than those in the lower section of the heart. Blood is not pumped out of the upper chambers completely during beating, and may pool and form a clot. A stroke results if a section of clot dislodges from the upper chambers and becomes lodged in the brain.
- International Normalized Ratio
- A system for assessing the clotting tendency of blood in patients receiving anticoagulant therapy. For patients with atrial fibrillation, the recommended target INR range is between 2 and 3. If the INR is higher than 3, patients are at risk of serious bleeding. If the INR is less than 2, patients are at risk of a blood clotting event.