Fibrillation thromboembolism risk

Recommended if patient is at high-risk of systemic thromboembolism (anterior wall infarction, heart failure, left ventricular thrombus, atrial fibrillation, previous embolism)... 

Treatment of atrial fibrillation is initiated to relieve patient symptoms and prevent the complications of thromboembolism and tachycardia-induced heart failure, the result of prolonged uncontrolled heart rates. The initial treatment objective is control of the ventricular response. This is usually achieved by use of a calcium channel-blocking drug alone or in combination with a 13-adrenergic blocker. Digoxin may be of value in the presence of heart failure. A second objective is a restoration and maintenance of normal sinus rhythm. Several studies show that rate control (maintenance of ventricular rate in the range of 60-80 bpm) has a better benefit-to-risk outcome than rhythm control (conversion to normal sinus rhythm) in the long-term health of patients with atrial fibrillation. If rhythm control is deemed desirable, sinus rhythm is usually restored by DC cardioversion in the USA in... 

The increased risk of thromboembolism associated with atrial fibrillation and with the placement of mechanical heart valves has long been recognized. Similarly, prolonged bed rest, high-risk surgical procedures, and the presence of cancer are clearly associated with an increased incidence of deep venous thrombosis and embolism. Antiphospholipid antibody syndrome is another important acquired risk factor. Drugs may function as synergistic risk factors in concert with inherited risk factors. 

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. 

Zabalgoitia M, et al. Transesophageal echocardiographic correlates of clinical risk of thromboembolism in nonvalvular atrial fibrillation. Stroke Prevention in Atrial Fibrillation III Investigators. J Am Coll Cardiol 1998 3 I (7) 1622-1626. 

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. 

Strachan DP, Carrington D, Mendall MA et al. (1999). Relation of Chlamydia pneumoniae serology to mortality and incidence of ischemic heart disease over 13 years in the Caerphilly Prospective Heart Disease Study. British Medical Journal 318 1035-1039 Stroke Prevention in Atrial Fibrillation Investigators (1992). Predictors of thromboembolism in atrial fibrillation II Echocardiographic features of patients at risk. Annals of Internal Medicine 116 6-12 Stroke Prevention in Atrial Fibrillation Investigators (1995). Risk factors for thromboembolism during aspirin therapy in patients with atrial fibrillation the Stroke Prevention in Atrial Fibrillation Study. Journal of Stroke and Cerebrovascular Disease 5 147-157... 

However, there is only one report specifically on which patients with a previous TIA or stroke and NRAF are at high (and low) risk, based on 375 patients with NRAF and TIA or non-disabling stroke treated in the placebo arm of the European Atrial Fibrillation Trial (van Latum et al. 1995). Independent risk factors for vascular death, stroke and other major vascular events included increasing age, previous thromboembolism, ischemic heart disease,... 

Oral H, Chugh A, Ozaydin M, et al. Risk of thromboembolic events after percutaneous left atrial radiofrequency ablation of atrial fibrillation. Circulation 2006 114 759—65. 

Marin et al. (M7) reported that patients with atrial fibrillation had lower levels of plasma MMP-1 but increased levels of TIMP-1 and prothrombin fragments FI 2 (an index of thrombogenesis) and higher ratios of TIMP-1 to MMP-1 as compared to control subjects. The authors proposed that MMP TIMP measurements in blood might be useful as markers of comorbidity that is associated with increased risk of stroke and thromboembolism in patients with atrial fibrillation. 

Atrial fibrillation (Afib) is the most common cardiac arrhythmia in the United States. Persons with Afib are at increased risk of blood clots in the heart that in turn may lead to thromboembolic stroke. The medication warfarin is often prescribed as a preventative measure. While the effectiveness of warfarin in the prevention of thromboembolic stroke is well established, its physiological mechanism of action also puts users at higher risk for other adverse events, for example, bleeding, whose health consequences may be just as devastating. Randomized clinical trials of warfarin have reported favorable results in both effectiveness and safety analyses. However, some clinicians have expressed doubt as to whether these results validly represent the situation in the general Afib patient population. The reason is that typical Afib patients tend to have more comorbidities and may not be as healthy as trial participants. 

---