6th March 2024

Atrial fibrillation (AF)

AF is characterised by chaotic atrial activity as a result of electrical discharge from multiple foci, predominantly within the pulmonary veins that drain into the left atrium. It is commonly an accompanying feature of hypertension or ischaemic heart disease. It can also be due to structural cardiac changes e.g. valve disease, hypertrophy or dilation, as well as an infiltrative or inflammatory process. More commonly, however, AF is seen as a result of non-cardiac causes, e.g. infection, hyperthyroidism, hyponatraemia, hypokalaemia and PE. Other factors such as caffeine, alcohol and smoking may also contribute to the development of AF. AF is also strongly correlated with obstructive sleep apnoea, obesity and metabolic syndrome. It is:

• Paroxysmal: if it occurs for less than 7 days (typically less than 48 hours)
• Persistent: if it continues beyond 7 days 
• Permanent: arrhythmia is longstanding, where cardioversion has failed and when it is accepted that no further attempts will be made to cardiovert. 

Patients may be asymptomatic or report palpitations, breathlessness, and fatigue. Where there is a rapid ventricular response or underlying coronary artery disease, chest pain may develop. Very rarely, AF may present with syncope. The ECG is characterised by an absence of p waves and irregularly irregular QRS complexes due to the variation in AV node conduction of the chaotic atrial electrical activity. 

Beyond the ECG, blood tests can help to confirm infection, thyroid dysfunction and electrolyte abnormalities including sodium, potassium, calcium and magnesium. An echocardiogram can assess for an underlying structural cause such as valvular pathology (i.e. mitral stenosis or regurgitation) but also look for left atrial dilation, which can inversely correlate with the success of rhythm control / management.