11 GENERAL INTRODUCTION effective in preventing ischaemic stroke but cause less (major) bleeding in patients with AF. However, the GP realises that frail old patients such as Mrs. de Jong were highly underrepresented in these pivotal trials. While thinking about how to minimise both the risk of stroke and the risk of bleeding as much as possible, the GP also considers switching to a NOAC with an off-label reduced NOAC dose. Eventually, the GP decides not to switch at all, because of the lack of evidence for either option. ATRIAL FIBRILLATION Atrial fibrillation (AF) is one of the most common cardiac conditions with a lifetime risk of one in three individuals of Western ancestry.3 AF is particularly common in the ageing population with a prevalence of 0.7% in people aged 55 to 59 years, rising to 17.8% in those aged 85 years and older,4 and rising even further to 38% in the most frail population in society (i.e. nursing home residents).5 Importantly, the overall prevalence of AF is increasing due to the ageing of the population and is expected to double within half a century.6 This has a major impact on public health as AF is associated with severe morbidity and mortality. The most feared complication of AF is the occurrence of an ischaemic stroke which, without anticoagulation, occurs nearly five times more often in patients with AF compared to patients without AF.7 However, it is important to note that this evidence dates back to 1991, which makes it very well possible that this risk is different in today’s AF population that generally suffers from more comorbidities but benefits from improved healthcare. To estimate stroke risk in untreated AF patients, prediction models have been developed, of which the CHA2DS2-VASc model is the most widely used.8 However, with a concordance-statistic for ischaemic stroke of 0.67 (95% confidence interval (95% CI) 0.66-0.68), the ability to predict stroke, in particular for intermediate and high risk patients, is not very accurate.1 Nevertheless, the European Society of Cardiology recommends oral anticoagulation therapy, with the aim to prevent stroke, when the CHA2DS2-VASc score is ≥2 points in men or ≥3 points in women.9,10 ANTICOAGULANTS Without anticoagulation, stroke risk can be as high as 14.4% per year in AF patients with multimorbidity, as summarised by the CHA2DS2-VASc risk model. 1 In 1989, the AFASAK study was the first randomised controlled trial (RCT) showing effectiveness of oral anticoagulation for stroke prevention in AF.11 During the years that followed, it became apparent that treatment with oral anticoagulants reduced the risk of an ischaemic stroke by 67% (95% CI 54%-77%).2 Until 2008, the only type of oral 1
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