Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, and strokes seem to be becoming more prevalent.1–3 Nevertheless, as many AF patients are asymptomatic, current epidemiological estimates might underestimate the number of people with the arrhythmia.4
AF patients can present with a wide range of sometimes debilitating symptoms, disease patterns and co-morbidities. But even when asymptomatic, AF can cause irreversible remodelling of the atria, which can perpetuate the arrhythmia and mean that over time, AF becomes progressively difficult to treat.5,6 As a result, early detection and rapid effective treatment are the cornerstones of care to alleviate symptoms and to reduce the risk of complications, including AF-related stroke.5 This section of the Learning Zone explores the background to AF-related strokes.
In This Section
Epidemiology of Stroke
Stroke is common with, often, debilitating outcomes and the number of cases is set to rise markedly.
A common problem
Age-adjusted stroke incidence varies from 95–290 per 1,000,000 of the European population annually.3 About 1.1 million people experience a stroke in Europe each year. Transient ischaemic attacks (TIAs) are also common: the age-adjusted incidence ranged from 28–59 per 100,000 of the European population each year.3
Epidemiology of atrial fibrillation
AF is common in Europe, although the number of patients affected is probably underestimated.
AF incidence in Europe is between 21 and 41 per 100,000 of the population a year.2 AF prevalence in Europe varies from 1.9–2.9%.2,4,12
Classification of atrial fibrillation
Atrial fibrillation (AF) can present in several ways and correct classification can guide the choice of treatment. AF can present in several ways (Table 2) from a single isolated episode to a constant arrhythmia.
Atrial fibrillation: an important stroke risk factor
The relationship runs both ways; atrial fibrillation (AF) causes strokes, while strokes can trigger AF.
The relationship between AF and stroke runs both ways. On the one hand, AF markedly increases the risk of stroke and systemic embolism.6
For instance, AF increases stroke risk five-fold compared with people without the arrhythmia.2,6 The risk associated with AF is even higher in people with other stroke risk factors.20 Overall, AF may cause up to half of cardioembolic strokes and 10–30% of acute ischaemic strokes.4,11,19
Pathophysiology of atrial fibrillation
A network of pathways influences the onset and persistence of atrial fibrillation (AF).
In any particular patient, the onset and persistence of AF may involve a complex network of mutually reinforcing pathogenic pathways that are influenced by age, genetic factors and acquired risk factors.6,25
For example, acute coronary syndrome (ACS), such as myocardial infarction, as well as surgery or infection seem to precipitate a third of AF cases.19 Table 3 summaries the possible pathophysiology of different AF types, which may overlap in clinical practice.5 This section takes a deep dive into the pathophysiology of this common arrhythmia.
Pathophysiology of stroke in people with atrial fibrillation
Almost all AF patients show the pathophysiological changes that increase stroke risk.
AF’s characteristic aberrant electrical activity means that the atria do have time to contract and move the blood into the ventricles. So, blood remains in the atria and a clot may form. This, in turn, may embolise resulting in an ischaemic stroke.32
Even short AF episodes can damage the atrial endothelium, which expresses factors that activate the coagulation cascade and as well as activating platelets and inflammatory cells. As a result, even short AF episodes can increase stroke risk.5
Symptoms of atrial fibrillation
Atrial fibrillation (AF) patients can present with a range of symptoms, but these are a poor guide to diagnosis.
AF patients may present with heart failure, myocardial infarction or another ACS, stroke or haemodynamic collapse and a variety of other, typically, non-specific symptoms (Figure 7).32
Diagnosis and diagnostic recommendations of atrial fibrillation
Atrial fibrillation diagnosis can be challenging, but ECG monitoring is the foundation of assessment.
An irregular pulse should raise a suspicion of AF: the sensitivity and specificity of pulse rate for AF is 94% and 72% respectively.19,32 Clinical presentation (Table 5) may indicate the type of AF, although about a third of AF episodes are asymptomatic.5,19
Burden of atrial fibrillation
AF impairs patients’ quality of life and accounts for up to 2% of healthcare budgets; stroke and hospitalisations drive the costs.
AF patients report impaired quality of life (QoL) that is independent of concomitant cardiovascular conditions.5 The impairment in QoL associated with AF can be similar to that in CHF and reflects the symptoms of the disease and complications, such as stroke.35
AF’s impact on QoL may be especially marked in women, younger patients and those with comorbid conditions, such as coronary artery disease, COPD, obstructive sleep apnea or New York Heart Association (NYHA) classes II-IV CHF. Some of these factors could be modified and their presence may indicate that the patient requires a thorough QoL assessment.35
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