Future directions and conclusions
In spite of the acknowledged bleeding risks of warfarin therapy, and the logistical burden involved in monitoring INRs and adjusting warfarin dosing, oral anticoagulation is an invaluable tool to prevent the severe consequences of stroke or other cardioembolic events. There would be tremendous value in developing agents that provide the anticoagulant effects of warfarin without the need for ongoing monitoring and with fewer drug interactions. Such agents are currently being tested in large phase 3 randomized trials. In the meantime, treatment of patients with AF will require continued clinical vigilance using approaches that balance the risks and benefits of the tools available today.
Stroke Prevention in Atrial Fibrillation – The Unmet Need and Morbidity Burden
Atrial fibrillation (AF) occurs in epidemic proportion and is now recognised to occur in about 2 % of the general population. Its prevalence is age-related – about 10 % of 80-year-olds have this arrhythmia with hypertension, valvular disease and heart failure being the most frequent underlying conditions. Up to 10 % of cases of AF may be idiopathic, although genetic, autonomic, inflammatory, infective and toxic causes may account for many of these. AF is associated with serious consequences of which death, sudden death, stroke, heart failure, pulmonary disease and hospitalisation are the most serious. Thromboembolic stroke occurs in about 5 % of AF patients each year, which is approximately five-fold the stroke rate in age and gender-matched patients without AF. AF-related thromboembolic stroke accounts for 15–20 % of all strokes. Risk factors for thromboembolic stroke include clinical factors (such as age, female gender, diabetes, heart failure, hypertension, renal failure and arterial disease), elevated levels of biomarkers (such as troponin, B-type natriuretic peptide, C-reactive protein and micro-albuminuria) and echocardiographic features (such as left ventricular systolic dysfunction, increased left atrial size, left atrial ‘smoke’ and thrombus). There are several clinical risk stratification schemes used to identify AF patients at high risk of thromboembolic stroke. The CHADS2 scheme is popular, but tends to group a high proportion of patients in low and intermediate risk
categories. The recently introduced CHA2DS2-VASc scheme identifies truly low-risk patients and avoids placing more than a small proportion in a low or intermediate risk category where there is a guideline mandated choice between anticoagulant, antiplatelet or no therapy. This scheme, which is well validated, has been recommended by the European Society of Cardiology in anticipation of the introduction of new and safer oral anticoagulants. Although warfarin is an effective therapy for the prevention of thromboembolic complications of AF it is inadequately used because of fear of haemorrhagic complications and the difficulties associated with monitoring and maintenance of the correct level of anticoagulation. At present, as few as 20 % of patients who should be anticoagulated are effectively treated. New anticoagulant therapies, which are much easier to use, coupled with more attention to the indications for anticoagulation, should result in more effective anticoagulation and a major reduction in the thromboembolic complications associated
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with AF.
Atrial fibrillation (AF), a major cause of morbidity and mortality in the Western world, is considered to be a rising epidemic. 1–3 In the US alone, approximately 2.7 million people are affected by AF 4 and this figure is projected to increase to an estimated 16 million by 2050.
The rising prevalence of AF is mainly attributable to the ageing population 6 and survival from other cardiovascular disease. AF predominantly affects individuals over 80 years of age.
AF is a strong independent risk factor for stroke and accounts for one in five strokes. 9 Furthermore, stroke in AF has twice the mortality rate compared to other strokes, 1 is a cause of severe disability compared to other strokes, 10 more frequent hospital stays 3 and is a major socioeconomic burden. 11 Anticoagulation therapy with warfarin is recommended by evidence-based guidelines for stroke prevention in patients with AF and is widely regarded as the standard of care.
However, warfarin therapy has severe limitations that make it difficult and inconvenient to use in clinical practice. 13 Consequently, up to 50 % of AF patients at moderate to high risk of stroke do not receive appropriate anticoagulant treatment. 14–19 Thus, there is an urgent need for improved antithrombotic therapy in AF management. This article aims to review the clinical consequences of stroke in AF and the recent improvements in risk stratification.
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