Atrial fibrillation is among the most examinable cardiology topics because it tests three decisions at once: rate versus rhythm control, stroke-risk assessment, and the choice of anticoagulant. This guide covers the essentials to the current NICE standard (NG196). Follow current guidance and local protocols in practice; this reflects NICE guidance as of mid-2026.
What AF is
Atrial fibrillation is a supraventricular arrhythmia with disorganised atrial activity, giving an irregularly irregular pulse and loss of effective atrial contraction. The clinical risks are twofold: symptoms and haemodynamic compromise from the rate, and stroke from atrial thrombus, particularly in the left atrial appendage. Examiners often probe the underlying cause, which guides management: common precipitants and associations include hypertension, ischaemic and valvular heart disease, heart failure, hyperthyroidism, alcohol excess, sepsis and pneumonia, pulmonary embolism, and electrolyte disturbance. Identifying and treating a reversible trigger — thyrotoxicosis or infection, for instance — is part of the answer, not just rate or rhythm control.
Diagnosis
An irregular pulse should prompt a 12-lead ECG, which shows absent P waves and an irregularly irregular rhythm. Where paroxysmal AF is suspected but not captured, ambulatory monitoring (such as a 24-hour ECG) is used. Less than half of people with AF report palpitations, so it is often found incidentally — a point worth remembering. AF is also classified by its pattern, which examiners expect you to use precisely: paroxysmal AF terminates spontaneously, usually within 48 hours and certainly within seven days; persistent AF lasts longer than seven days or requires cardioversion to terminate; and permanent AF is established and accepted, with a rate-control strategy adopted. The pattern influences whether rhythm control is realistic. A first detected episode is described as such regardless of duration or symptoms, and may prove paroxysmal, persistent or permanent on later assessment.
Two parallel decisions
NICE frames management as two separate questions answered in parallel: how to control the rhythm or rate, and how to prevent stroke.
Rate or rhythm control: for most people, rate control is first-line — a standard beta-blocker (not sotalol) or a rate-limiting calcium-channel blocker (diltiazem or verapamil), with digoxin reserved for largely sedentary patients. Rhythm control is preferred in specific situations: new-onset AF (within 48 hours), AF with a reversible cause, heart failure thought to be caused by the AF, or where symptoms persist despite rate control. Acutely, a patient who is haemodynamically unstable needs emergency electrical cardioversion. A regularised, very fast rhythm or signs of pre-excitation should prompt senior input, as some rate-controlling agents are unsafe in AF with Wolff–Parkinson–White. AF can itself cause or worsen heart failure through a persistently fast, irregular rate, a reversible contributor worth recognising.
Stroke prevention: assess stroke risk with CHA2DS2-VASc. Offer anticoagulation at a score of 2 or above; consider it in men with a score of 1; and do not anticoagulate where female sex is the sole risk factor. Assess bleeding risk with the ORBIT score — which NICE now prefers over HAS-BLED — but use it to identify and modify risk factors, not as a reason to withhold anticoagulation.
The anticoagulant: a direct-acting oral anticoagulant (apixaban, dabigatran, edoxaban or rivaroxaban) is first-line. Warfarin is reserved for those in whom a DOAC is unsuitable, such as people with mechanical heart valves, with a target INR of 2.5. Aspirin should not be used for stroke prevention in AF. The reason anticoagulation is taken so seriously is that AF roughly multiplies stroke risk fivefold, and AF-related strokes tend to be more severe and disabling than other ischaemic strokes — which is why bleeding risk is managed by modifying risk factors rather than by withholding effective treatment. The CHA2DS2-VASc components are worth knowing: congestive heart failure, hypertension, age 75 or over (two points), diabetes, prior stroke or TIA (two points), vascular disease, age 65 to 74, and female sex — with stroke and age 75-plus each scoring two and the rest one.
Cardioversion and anticoagulation timing
If AF has been present for more than 48 hours and elective cardioversion is planned, the patient needs at least three weeks of therapeutic anticoagulation beforehand (or a transoesophageal echo to exclude thrombus), continued for at least four weeks afterwards. This delay is to avoid dislodging an established atrial thrombus at the moment sinus rhythm returns. Within 48 hours of onset, cardioversion can proceed with appropriate anticoagulant cover.
High-yield exam points and traps
- DOAC first-line, not warfarin: a frequent update point since the 2021 guideline.
- No aspirin for stroke prevention in AF.
- ORBIT, not HAS-BLED, is the NICE-preferred bleeding score.
- Do not withhold anticoagulation because of age alone or a risk of falls.
- Bleeding risk is a prompt to modify risk factors (blood pressure, alcohol, NSAIDs), not to deny treatment.
- Rate control is first-line for most; know the exceptions favouring rhythm control.
- More than 48 hours of AF means anticoagulate before cardioversion.
- A pulse deficit — a faster apical than radial rate — is a classic bedside sign.
A few common questions
Which anticoagulant is first-line for AF? A direct-acting oral anticoagulant (apixaban, dabigatran, edoxaban or rivaroxaban); warfarin is reserved for cases such as mechanical valves.
When should anticoagulation be offered in AF? At a CHA2DS2-VASc score of 2 or above, and considered in men with a score of 1; not for sex alone.
Which bleeding-risk score does NICE recommend? ORBIT, which replaced HAS-BLED in the 2021 guideline; it guides risk-factor modification rather than withholding treatment, and is not intended to identify people who should not be anticoagulated.
Rate or rhythm control first? Rate control for most patients; rhythm control for new-onset AF, a reversible cause, AF-related heart failure, or persistent symptoms.
What are the types of AF? Paroxysmal (self-terminating, usually within 48 hours), persistent (lasting beyond seven days or needing cardioversion to terminate), and permanent (established and accepted, managed with rate control).
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