2.3 Atrial fibrillation

Atrial fibrillation (AF, an abnormal heart rhythm with rapid and irregular beating) is estimated to increase the risk of stroke 3 to 5-fold and to be associated with around a quarter of all ischaemic strokes[117-119]. Additionally, AF is associated with more severe strokes leading to higher mortality and disability[120].

2% of patients attending the emergency room with AF had a stroke within 1 year in Western Europe and 4% in Eastern Europe, according to a large international cohort study[121]. The 2016 European Society of Cardiology (ESC) Guidelines for AF Management[122] recommend that anyone over 65 years or at high risk of stroke is screened for atrial fibrillation.

AF is often asymptomatic and screening is not routinely undertaken in Europe. Accurate information on its prevalence in the general population is therefore not widely available. Some European countries have undertaken screening studies to estimate the proportion of the population affected (Appendix 1, Table 2). They reported rates in the general population ranging from 1.3% (UK, Italy) to 3.9% (Greece), with rates being highly dependent on age. Less data is available from Central and Eastern European countries.

Screening studies also found that between 10% and 66% of people with AF were previously unknown cases (Belgium[95], Portugal[123], UK[124], Spain[125]). This implies a significant under-diagnosis in Europe. A UK trial showed that opportunistic screening with simple pulse palpation resulted in significantly improved detection rates[126]. A major screening study has been launched in Sweden to detect AF and to see whether screening reduces stroke incidence and is cost effective[127].

AF is significantly more common in people who have had a stroke than in the general population. Reported prevalence rates are as high as 31-38% in a Greek study (Appendix 1, Table 1). Variations are also high within countries and studies with similar methodologies (e.g. Italy[128], Appendix 1, Table 1).

AF is often only diagnosed after someone has had a stroke: studies from Ireland[129], Iceland[16], Croatia[130] and Norway[131] reported that between a quarter to over half of AF diagnoses known after stroke were unknown before. A recent metaanalysis also reported that 24% of stroke patients are newly diagnosed with AF after their stroke[132]. These reports again suggest a significant under-diagnosis of AF in the general population. Better detection rates of AF could lead to improved primary prevention.

Due to Europe’s ageing population and AF’s strong association with age (0.7% in those aged 55-59 vs. 17.8% in those aged ≥85 years,[133]), the prevalence of AF is expected to rise. Using data from the communitybased Rotterdam Study and population projections from Eurostat, it was estimated that the number of adults over 55 with AF will more than double between 2010 and 2060 from 8.8 million to 17.9 million[117]. An Icelandic study projected the prevalence of AF to rise from 1.9% in 2008 to 3.5% in 2050[134].

In the UK, the number of AF related ischaemic strokes has trebled in the last 25 years in adults over 80 years and is predicted to treble again by 2050, with AF-related embolic events costing the UK around £374 million per year[135].

AF is therefore an important part of European[136, 137] and most national stroke guidelines, both for primary and secondary prevention. However, some European countries have not developed national guidelines covering AF treatment in relation to stroke primary prevention (Czech Republic, Greece, Latvia, Estonia,[9])

The ESC Guideline recommends treating AF patients following a structured risk assessment with oral anticoagulants for those with high risk scores[136]. Several recent, international European studies have assessed treatments rates of AF patients with oral anticoagulants (Table 8).

Table 8: International oral anticoagulants treatment  studies

*The CHA2DS2-VASc-score is a validated risk stratification scoring system, including congestive heart failure, hypertension, age, diabetes mellitus, stroke/TIA/ thromboembolism, vascular disease, and sex.

Generally, these studies found relatively high oral anticoagulant treatment rates, but treatment was often not in accordance with the guidelines and patients’ specific risk profiles. Under- use of oral anticoagulants in elderly patients[146] or those with high risk scores and over-use in those with low risk scores was observed.

Also, the majority of these studies recruited patients registered with cardiologists (PREFERAF, EORP-AF, BALKAN-AF, Euro Heart Survey, Gloria-AF). So the generally high treatment rates might not be representative for patients in primary care. Several smaller studies, particularly those using primary care data or data from screening studies, discovered much lower rates (Table 9). These figures might be more representative of real-life AF anticoagulant treatment. Again, a mismatch between treatment and patients’ risk scores was observed, showing poor adherence to guidelines.

Table 9: Oral anticoagulant treatment rates in national/regional studies

The spread of novel oral anticoagulants (NOAC) (now known as non-vitamin K antagonist oral anti-coagulation) will overcome some obstacles to the use of traditional oral anticoagulants (the need for frequent monitoring, for example), and might improve treatment rates. However, their uptake has been reported to be slow[138]: use of NOAC in Italy: <1%, UK: 4%, France: 6%, Spain: 11%, Germany: 12%. The National Health Service in England reported that most areas had a NOAC uptake below 20% of oral anticoagulants with wide variations (4%  to  69%)[165]. In Poland, 19% of anticoagulated AF patients discharged from cardiology were using NOAC[166]. More encouragingly, a German study of four tertiary stroke centres reported that half of ischaemic stroke patients discharged with anticoagulation were prescribed NOAC[167] and recent European data from GLORIA-AF show that 52.3% of all oral anticoagulant prescriptions for newly diagnosed AF patients were NOACs[145]. A recent Danish study found 73% of all prescribed oral anticoagulants being NOAC in 2015[148].

In conclusion, the prevalence of AF is expected to rise significantly over the next few decades due to an ageing population and there is evidence of severe under-diagnosis. Anticoagulation rates reported from large surveys using specialist cardiology set-ups are encouraging but studies using primary care data show much lower treatment rates, particularly in the older age group[156, 157]. Retrospective analyses of treatment rates in AF patients prior to stroke are lower still (16-39%).  Adherence to available treatment guidelines and the recommended use of risk stratification is still insufficient[168].

Treatment rates after stroke were higher, but still showed much room for improvement.