Lead editorial – Atrial fibrillation and stroke risk
Professor Gregory Y H Lip
Professor of Cardiovascular Medicine, University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Birmingham, UK
Atrial fibrillation (AF) is the commonest sustained cardiac rhythm disorder. It is associated with an increased mortality and morbidity from stroke and thromboembolism. Oral anticoagulation reduces the risk of stroke by two-thirds. Until fairly recently, the only way of administering such thromboprophylaxis was by the use of vitamin K antagonists, such as warfarin the use of which is associated with important lifestyle limitations and International Normalised Ratio (INR) monitoring so as to ensure that patients keep within a therapeutic INR range of 2.0–3.0. Given the significant inter and intra-patient variability in INR, many clinicians and patients do not like using warfarin. In patients who refuse warfarin, or have had ‘failed’ warfarin therapy due to difficulties in attending for anticoagulation monitoring or an inability to keep safely within the target INR range, many guidelines have recommended the use of antiplatelet therapy but there is now clear evidence that aspirin is inferior to warfarin for stroke prevention, and the rates of major bleeding (or intracranial haemorrhage) may not be much different between aspirin and warfarin, especially in the elderly.
As patients with AF get older, the absolute benefit of oral anticoagulation increases, and the absolute benefit of antiplatelet therapy declines Given the availability of new oral anticoagulants that overcome the disutility of warfarin and the recognition that aspirin is an inferior choice (and not much safer), the focus has been directed towards improving the identification of the ‘truly low risk’ AF patients who need no antithrombotic therapy, whilst patients with one or more stroke risk factors should be considered for oral anticoagulation. The most commonly used and simple stroke risk stratification scheme is the CHADS2 [Cardiac failure, Hypertension, Age, Diabetes, Stroke (Doubled)] score, To be more inclusive – rather than exclusive – of stroke risk factors, the CHA2DS2-VASc score has been proposed, to complement the CHADS2 score.