Atrial fibrillation warfarin

And history of atrial fibrillation or previous systemic embolism o Warfarin administered to achieve an INR of 2.5 (range 2-3). 

Warfarin has been the primary oral anticoagulant used in the United States for the past 60 years. Warfarin is the anticoagulant of choice when long-term or extended anticoagulation is required. Warfarin is FDA-approved for the prevention and treatment of VTE, as well as the prevention of thromboembolic complications in patients with myocardial infarction, atrial fibrillation, and heart valve replacement. While very effective, warfarin has a narrow therapeutic index, requiring frequent dose adjustments and careful patient monitoring.15,29... 

Warfarin has not been adequately studied in non-cardioembolic stroke, but it is often recommended in patients after antiplatelet agents fail. One small retrospective study suggests that warfarin is better than aspirin.30 More recent clinical trials have not found oral anticoagulation in those patients without atrial fibrillation or carotid stenosis to be better than antiplatelet therapy. In the majority of patients without atrial fibrillation, antiplatelet therapy is recommended over warfarin. In patients with atrial fibrillation, long-term anticoagulation with warfarin is recommended and is effective in both primary and secondary prevention of stroke.12 The goal International Normalized Ratio (INR) for this indication is 2 to 3. 

Anticoagulant drugs include heparin and warfarin (Coumadin ) —agents used to prevent deep vein thrombosis. They are also used to prevent formation of emboli due to atrial fibrillation, valvular heart disease, and other cardiac disorders. Heparin, which is not absorbed by the gastrointestinal tract, is available only by injection its effect is immediate. 

Warfarin is the antithrombotic agent of first choice for secondary prevention in patients with atrial fibrillation and a presumed cardiac source of embolism. 

Reiffel JA. Will direct thrombin inhibitors replace warfarin for preventing embolic events in atrial fibrillation Curr Opin Cardiol 2004 19 58-63. 

Johnson CE, Lim WK, Workman BS. People aged over 75 in atrial fibrillation on warfarin the rate of major hemorrhage and stroke in more than 500 patient-years of follow-up. J Am Geriatr Soc 2005 53 655-659. 

Clinicians from Hong Kong reported a case of potential danshen-warfarin interaction in a 48-year-old female with a history of rheumatic heart disease, atrial fibrillation, and mitral stenosis (11). The patient underwent successful transvenous mitral valvuloplasty for management of her medical conditions, and was discharged with 1 mg warfarin, as well as... 

Poller, L. and F.R.C. Path The Effect of Low Dose Warfarin on the Risk of Stroke in Patients with Nonrheumatic Atrial Fibrillation, New Eng J. Med.. 129 (July 1L 1992),... 

More than 50% of patients with cerebral embolism have atrial fibrillation. In the majority of these patients, the underlying cardiac disease is nonvalvular. The risk of ischemic stroke and atrial fibrillation increases with age, reaching a cumulative risk of 35% during a patient s lifetime. Combined results from several randomized trials show that warfarin reduces the risk of stroke in patients with nonrheumatic atrial fibrillation by 68% (to 1.4% per year), with an excess incidence of major hemorrhage (including intracranial) of only 0.3% per year. 

The risk of embolism associated with mechanical heart valves is 2 to 6% per patient per year despite anticoagulation and is highest with valves in the mitral position. Warfarin therapy (INR 2.5 to 3.5) is recommended in these patients. The addition of enteric-coated aspirin (100 mg/d) to warfarin (INR 3.0 to 4.5) in high-risk patients (preoperative atrial fibrillation, coronary artery disease, history of thromboembolism) with mechanical valves decreases the incidence of systemic embolism and death from vascular causes (1.9 vs. 8.5% per year), but increases the risk of bleeding. 

Rheumatic mitral valve disease is associated with thromboembolic complications at reported rates of 1.5 to 4.7% per year the incidence in patients with mitral stenosis is approximately 1.5 to 2 times that in patients with mitral regurgitation. The presence of atrial fibrillation is the single most important risk factor for thromboembolism in valvular disease, increasing the incidence of thromboembolism in both mitral stenosis and regurgitation four- to sevenfold. In current practice, patients with nonrheumatic atrial fibrillation at low risk for thromboembolism based on clinical characteristics frequently are treated with aspirin. Warfarin therapy is considered in higher-risk patients, especially those with previous thromboembolism and in whom anticoagulation is not contraindicated due to preexisting conditions. 

SPORTIF III Stroke prevention in nonvalvular atrial fibrillation Open-label 36 mg twice daily for at least 12 months Warfarin, target INR, 2.0-3.0 1704 1703 (60,83)... 

Atrial fibrillation is increasing in incidence in developed countries and, because of the risk of embolic stroke, most patients require continuous anticoagulation. A large number of patients with atrial fibrillation are currently treated with vitamin K antagonists. Results of clinical trials in patients with atrial fibrillation indicate that oral direct TIs may become potential drugs for the prevention of embolic stroke and may replace warfarin (62,78,79-81). 

Olsson SB. Stroke prevention with the oral direct thrombin inhibitor ximelagatran compared with warfarin in patients with non-valvular atrial fibrillation (SPORTIF III) randomised controlled trial. Lancet 2003 362 1691-1698. 

Albers GW, Diener HC, Frison L, et al. Ximelagatran vs warfarin for stroke prevention in patients with nonvalvular atrial fibrillation a randomized trial. J Am Med Assoc 2005 293 690-698. 

Lip GY Edwards SJ. Stroke prevention with aspirin, warfarin and ximelagatran in patients with non-valvular atrial fibrillation A systematic review and meta-analysis. Thromb Res 2006 ... 

Halperin JL. Ximelagatran compared with warfarin for prevention of thromboembolism in patients with nonvalvular atrial fibrillation Rationale, objectives, and design of a pair of clinical studies and baseline patient characteristics (SPORTIF III and V). Am Heart J 2003 146 431-438. 

Stafford RS, Singer DE. Recent national patterns of warfarin use in atrial fibrillation. Circulation 1998 97(13) 1231-1233. 

Bungard TJ, et al. Why do patients with atrial fibrillation not receive warfarin Arch Intern Med 2000 160( I ) 41 -46. 

The anticoagulant warfarin is increasingly used to prevent thromboembolic complications in patients with atrial fibrillation. The drug is administered as racemate, and bio-inactivation of the active S-enantiomer is accomplished by CYP2C9. Relatively common variants in CYP2C9 that reduce its function have been described, and homozygotes for reduction of function alleles... 

Hannah s ECG shows an abnormal heart beat she has now developed atrial fibrillation. Hannah is prescribed digoxin and an anticoagulant, warfarin. 

Q14 Warfarin is an orally active anticoagulant used in the treatment of valvular disease and atrial fibrillation. It is structurally similar to vitamin K, a compound which is required for the synthesis of prothrombin and several other clotting factors in the liver. Warfarin interferes with the actions of vitamin K and so reduces the risk of blood clotting. When taken by mouth, its effect is not immediate and it takes several days to achieve the maximal clinical effect. 

Some of the association between atrial fibrillation and stroke must be coincidental because atrial fibrillation can be caused by coronary and hypertensive heart disease, both of which may be associated with atheromatous disease or primary intracerebral hemorrhage. Although anticoagulation markedly reduces the risk of first or recurrent stroke, this is not necessarily evidence for causality because this treatment may be working in other ways, such as by inhibiting artery-to-artery embolism, although trials of warfarin in secondary prevention of stroke in sinus rhythm have shown no benefit over aspirin (Ch. 24). 

Fig. 7.2. A patient presenting with atrial fibrillation and a transient ischemic attack was found to have a cerebellar microbleed on gradient echo MRI (a) and was started on stroke prevention with aspirin rather than warfarin. Six months later, this patient had a symptomatic hemorrhage at the same site (b).

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