Atrial Fibrillation: Stroke Prevention, Rate and Rhythm Control

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. Disorganised electrical activity in the atria causes an irregular and often fast heart rate. Its biggest danger is stroke, because blood can clot in the poorly contracting left atrium.

Types

• Paroxysmal — stops by itself or with treatment within 7 days.
• Persistent — lasts more than 7 days.
• Long-standing persistent — continuous for more than 12 months when a rhythm-control strategy is chosen.
• Permanent — the patient and doctor accept AF and no further attempts at rhythm control are made.

Causes and risk factors

• Hypertension.
• Ischaemic heart disease and heart failure.
• Valvular disease, especially mitral stenosis (often rheumatic).
• Hyperthyroidism.
• Alcohol excess ("holiday heart").
• Obesity and sleep apnoea.
• Acute infection and sepsis.
• Electrolyte disturbance.
• After cardiac surgery.
• Increasing age.

Clinical features

Patients may have palpitations, breathlessness, dizziness, chest discomfort or fatigue, but many have no symptoms. On examination the pulse is irregularly irregular, and there may be a pulse deficit (the apex rate is higher than the radial rate).

Investigations

• 12-lead ECG: irregularly irregular rhythm, no distinct P waves, a fibrillating baseline.
• Ambulatory ECG monitoring if paroxysmal AF is suspected.
• Blood tests: thyroid function, electrolytes, kidney and liver function, full blood count.
• Echocardiography: valve disease, atrial size and ventricular function.

Management

1. Is the patient unstable?

AF with shock, syncope, myocardial ischaemia or severe heart failure needs urgent electrical (DC) cardioversion.

2. Prevent stroke

Assess stroke risk with a validated score (CHA₂DS₂-VASc; recent European guidance uses CHA₂DS₂-VA) and bleeding risk. Most patients with risk factors need anticoagulation. Direct oral anticoagulants (for example apixaban or rivaroxaban) are generally preferred, but warfarin is used in moderate-to-severe mitral stenosis and mechanical heart valves. Aspirin is not recommended for stroke prevention in AF.

3. Rate or rhythm control

• Rate control: beta-blocker or a rate-limiting calcium channel blocker (diltiazem or verapamil; avoid in reduced ejection fraction). Digoxin is an option in sedentary patients or heart failure.
• Rhythm control: cardioversion (electrical or drug, for example flecainide if there is no structural heart disease, or amiodarone), antiarrhythmic drugs, or catheter ablation in selected patients.
• If AF has lasted 48 hours or more (or onset is unknown), the patient needs at least 3 weeks of anticoagulation, or a transoesophageal echo to exclude clot, before elective cardioversion.

4. Treat the cause

For example thyroid disease, infection, alcohol, hypertension or sleep apnoea.

Exam pearls

• "Irregularly irregular pulse" in an exam stem means AF until proven otherwise.
• Always discuss stroke prevention. It is the most important long-term decision.
• Check thyroid function in new AF.

See also Reading an ECG, our ECG Basics Simplified note and the Medicine Companion.

Test yourself

5 exam-style single-best-answer questions. Choose your answer, then tap “Show answer”.

1. A patient has AF with hypotension, chest pain and confusion. What is the immediate treatment?

   1. Observation
   2. Digoxin orally
   3. Synchronised DC cardioversion
   4. Start a DOAC and review in 3 weeks
   5. Oral beta-blocker
   Show answer

   Answer: C. Synchronised DC cardioversion
   Haemodynamically unstable AF needs urgent electrical cardioversion.

2. Which anticoagulant is used in AF with moderate-to-severe mitral stenosis?

   1. Apixaban
   2. Rivaroxaban
   3. Aspirin
   4. Warfarin
   5. Dabigatran
   Show answer

   Answer: D. Warfarin
   Warfarin is used for AF with moderate-to-severe mitral stenosis or mechanical valves; DOACs are not recommended there.

3. Which rate-control drug should be avoided in heart failure with reduced ejection fraction?

   1. Bisoprolol
   2. Metoprolol
   3. Digoxin
   4. Carvedilol
   5. Verapamil
   Show answer

   Answer: E. Verapamil
   Rate-limiting calcium channel blockers (verapamil, diltiazem) are negatively inotropic and avoided in HFrEF.

4. Which blood test should be checked in all new AF?

   1. Vitamin D
   2. Amylase
   3. Thyroid function
   4. Serum ACE
   5. Ferritin
   Show answer

   Answer: C. Thyroid function
   Hyperthyroidism is an important reversible cause of AF.

5. AF of unknown duration: what is needed before elective cardioversion?

   1. Nothing
   2. At least 3 weeks of anticoagulation or a TOE to exclude atrial thrombus
   3. Digoxin loading
   4. An exercise test
   5. Aspirin for 1 day
   Show answer

   Answer: B. At least 3 weeks of anticoagulation or a TOE to exclude atrial thrombus
   If AF has lasted 48 hours or more (or onset is unknown), the risk of stroke after cardioversion requires prior anticoagulation or TOE.

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Disclaimer

For education and exam preparation only. This is not medical advice and must not be used to diagnose or treat patients. Always follow current clinical guidelines and the advice of qualified senior colleagues.