Anticoagulation atrial fibrillation

Coumarin is also widely used for long-term anticoagulation in chronic atrial fibrillation (particularly to avoid cardioembolic strokes), to prevent DVT or PE in patients with chronic hypercoagulability (e.g., congenital AT or protein C deficiency), or to prevent... 

Duration of atrial fibrillation/atrial flutter >48 h or unknown, o Electrical or chemical cardioversion in a patient without adequate anticoagulation may cause embolization of atrial thrombi. 

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. 

Kondstaal P. Anticoagulants for preventing stroke in patients with nonrheumatic atrial fibrillation and a history of stroke or transient ischemic attacks. Cochrane Database Syst Rev 1999. Issue 4. 

Restoration of sinus rhythm in atrial fibrillation may dislodge thrombi that have developed as a result of stasis in the enlarged left atrium. The risk of stroke and systemic arterial embolism is decreased by anticoagulation in such patients. 

A major focus of drug development has been to develop orally active anticoagulants that do not require monitoring. Rivaroxiban is the first oral factor Xa inhibitor to reach phase III clinical trials. The safety and efficacy of rivaroxiban appears to be at least equivalent, and possibly superior, to LMW heparins for prevention of deep vein thrombosis no routine monitoring is required. This drug is also in clinical trials for treatment of deep vein thrombosis and prevention of stroke in atrial fibrillation. 

Recent evidence indicates that many patients with atrial fibrillation—a very common arrhythmia in the elderly—do as well with simple control of ventricular rate as with conversion to normal sinus rhythm. Measures (such as anticoagulant drugs) should be taken to reduce the risk of thromboembolism in chronic atrial fibrillation. 

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. 

The burden and risks due to atrial fibrillation (AF) are high. The prevention of arterial emboli and particularly cerebral emboli implies oral anticoagulation (OAC). However, anticoagulant therapies are associated with a greater risk of major... 

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). 

Halperin JL. Ximelagatran oral direct thrombin inhibition as anticoagulant therapy in atrial fibrillation. J Am Coll Cardiol 2005 45 1-9. 

Anticoagulation during catheter procedures in atrial fibrillation... 

Anticoagulation in radiofrequency ablation of atrial fibrillation and atrial flutter... 

Bjerkelund CJ, Orning OM. The efficacy of anticoagulant therapy in preventing embolism related to D.C. electrical conversion of atrial fibrillation. Am J Cardiol 1969 23(2) 208—216. 

Arnold AZ, et al. Role of prophylactic anticoagulation for direct current cardioversion in patients with atrial fibrillation or atrial flutter. J Am Coll Cardiol 1992 19(4) 851-855. 

UFH anticoagulation is routinely used during vascular and cardiac surgery, for the prophylaxis and treatment of DVT for the prevention of pulmonary embolism in surgical patients, and in patients with atrial fibrillation and recent embolization (6). 

Approximately 25% of all patients with hypertrophic cardiomyopathy (HCM) have latent left ventricular outflow obstruction with an intraventricular gradient (I). Pathophysiologic features are asymmetric hypertrophy of the septum and a systolic anterior movement of the anterior leaflet. Medical treatment includes betablockers, and calcium antagonists of the verapamil type. Approximately 5— 10% of the patients with outflow obstruction are refractory to such negative inotropic therapy (2). Positive inotropic drugs such as digitalis or sympathomimetics are strictly contraindicated. In the presence of atrial fibrillation, anticoagulation therapy should be started. Since endocarditis is more common in patients with HCM because of turbulence in the left ventricle, prophylactic antibiotics should be administered for periods of potential bacteraemia. 

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... 

P-Blockers are the drugs of choice in atrial fibrillation because they decrease heart rate and promote conversion to sinus rhythm. Longterm, low-dose anticoagulant therapy reduces the risk of stroke that Is associated with atriai fibrillation. 

The overall risk of stroke should be assessed for each individual with atrial fibrillation. It should also be reassessed regularly, as a person s risk of stroke will change over time. The individual s attitude to anticoagulation will strongly influence the cost/benefit of treatment, and should always be taken into account. 

She has a 4 month history of chronic atrial fibrillation (AF) and is attending her local community pharmacy anticoagulant clinic. Her current prescription is ... 

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

Q13 Arterial emboli, which can block blood vessels and cause ischaemia or infarction in the tissues they affect, tend to originate in the left heart and are associated with valvular disease and dysrhythmias. Mitral stenosis is associated with abnormal atrial rhythm, particularly atrial fibrillation. Fibrillation and other rhythm abnormalities in the atria favour blood coagulation, resulting in production of thromboemboli which can move to distant parts of the circulation, such as the cerebral circulation. Thrombi could also form on surfaces of valves distorted by calcification and other abnormalities. In view of the risks of thromboembolism, it is usual to provide anticoagulant therapy to patients with mitral valve problems and atrial fibrillation. 

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. 

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