Stroke Prevention in Atrial Fibrillation – The Unmet Need and Morbidity Burden

Abstract

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 with AF.