More patients with atrial fibrillation need to be anticoagulated

In an increasingly aging population, atrial fibrillation (AF) becomes more frequent and cardio-embolic stroke will become more prevalent. Patients with AF have a five times higher stroke risk. Cardio-embolic strokes in patients with AF are more severe and have a higher mortality. Long-term oral anticoagulation in patients with AF with the vitamin K antagonist warfarin was very effective in stroke prevention in several randomized placebo-controlled trials [1,2]. Warfarin reduced the overall risk of stroke on average by 64% compared with placebo in non-valvular patients with AF as shown in a meta-analysis by Hart et al. [3]. Warfarin led to a small absolute increase in major extracranial hemorrhage of 0.3%. Adjusted-dose warfarin (INR 2.0–3.0) is also significantly more effective than aspirin therapy in primary and secondary stroke prevention leading to a relative risk reduction of 39% [3]. At present, in most healthcare systems, a major challenge is the high proportion of patients with AF who remain untreated or receive aspirin instead of oral anticoagulation. Part of the explanation are the many shortcomings of vitamin K antagonists such as variable pharmacodynamics and pharmacokinetics, requiring frequent INR control, multiple interactions with food and other drugs, and the risk of major bleeds, in particular intracranial bleeds. Another problem is the difficult decision to be taken by a treating physician to balance the benefit of stroke prevention versus the risk of major bleeds. The CHADS2 score was developed [4] to identify patients with AF at high enough risk of stroke to warrant antithrombotic treatment. The paper by Giralt-Steinhauer in this issue of European Journal of Neurology [5] reports data from a hospital-based cohort of stroke patients prospectively collected between 2003 and 2011. The authors only analyzed patients who at the time of their first ischaemic stroke had known non-valvular AF or had newly detected AF. The study has all the shortcomings of a hospital-based study with many biases. Nevertheless, the paper has two important messages: 1 Only a minority of patients with AF are anticoagulated at the time of their ischaemic stroke and even those who are anticoagulated are frequently undertreated defined by an INR < 2. Only 32% of patients with known AF and a CHADS2 score of 2 were anticoagulated at the time of the first stroke, and in half of them, the INR was below 2. 2 The newly developed CHA2DS2-VASc score [6] seems to be more appropriate to identify patients with AF at moderate or high risk of stroke in need of oral anticoagulation. Whilst the CHADS2 score placed 24% of patients in the low–intermediate risk group requiring no therapy or aspirin, the CHA2DS2-VASc score put only 3.6% of patients in this category. What are the lessons to be learned? Recently, three new oral anticoagulants were investigated in patients with AF and compared with warfarin [7–9] or aspirin [10]. These new anticoagulants were at least as effective as warfarin or superior in preventing strokes and had a comparable or lower rate of major bleeds. All new anticoagulants decreased dramatically the risk of intracranial bleeds. Apixaban was superior to aspirin with a comparable bleeding risk. At present, much of the debate on new anticoagulants concentrates on the question whether and which patients with AF on warfarin should be switched to one of the new anticoagulants. However, this is not the most important issue. The real issue is to get untreated patients with AF who have no contraindication on oral anticoagulation and to switch those on aspirin (which is not better than placebo) to oral anticoagulation. This goal might be achieved much more easily with the new anticoagulants. Neurologists on stroke units do not have to obsess about the CHADS score. All our patients with a TIA or ischaemic stroke and AF fulfill the criteria for anticoagulation. Therefore, we only have to check which patient has contraindications.