Atrial Fibrillation

AF definition, causes, investigation and management.

What is Atrial Fibrillation (AF)?

A supraventricular tachyarrhythmia with disorganised atrial electrical activity and ineffective atrial contraction. The ventricular response is usually irregular because conduction through the atrioventricular node varies.

What are the mechanisms and consequent clinical consequences of AF?

• Loss of effective atrial systole leads to:

  • Reduced ventricular filling and cardiac output, particularly with diastolic dysfunction or mitral stenosis.

• Irregular and sometimes rapid ventricular response leads to:

  • Palpitations, impaired exercise capacity and, if persistent, tachycardia-induced cardiomyopathy.

• Left atrial and appendage stasis leads to:

  • Thrombus formation with risk of stroke or systemic embolism.

• Atrial structural and electrical remodelling leads to:

  • AF becomes more likely to recur and progress over time.

What are the four different types of AF, classed according to duration of episodes?

• Paroxysmal

• Persistent

• Long-standing persistent

• Permanent

Paroxysmal AF

One or more episodes of AF which terminate spontaneously or with intervention within 7 days.

Persistent AF

One or more episodes that continue for more than 7 days, including episodes terminated by cardioversion after 7 days or longer.

Long standing persistent AF

Continuous AF for 12 months or longer when rhythm control remains a treatment goal.

Permanent AF

When the patient lives with atrial fibrillation long-term, and no further attempt or treatment is panned to restore or maintain sinus rhythm.

What are the different precipitants to AF?

It typically reflects underlying cardiovascular disease, but acute illness may precipitate a first / recurrent episode:

• Cardiovascular precipitants

• Respiratory precipitants

• Metabolic / Endocrine precipitants

• Systemic illnesses precipitants

• Lifestyle and related factors

What are the main cardiovascular precipitants to AF?

• Hypertension

• Heart failure

• Ischaemic heart disease

• Cardiomyopathy

• Valvular disease

• Myocarditis

• Pericarditis

• Cardiac surgery

What are the main respiratory precipitants to AF?

• Pneumonia

• Pulmonary embolism

• Hypoxia

• Exacerbation of chronic lung disease

What are the main metabolic / endocrine precipitants to AF?

• Hyperthyroidism

• Hypokalaemia

• Hypomagnasaemia

• Diabetes

• Obesity

What are the main systemic illnesses that can precipitate AF?

• Sepsis

• Anaemia

• Hypovolaemia

• Major non-cardiac surgery

What lifestyle factors may precipitate AF?

• Alcohol excess

• Stimulant drugs

• Obstructive sleep apnoea

• Physical inactivity

Does AF always present with symptoms?

No, it can be symptomless and detected incidentally. Symptoms can be very minimal or more major.

What are the symptoms AF can present with?

• Palpitations / awareness of an irregular heartbeat

• Breathlessness, fatigue, or reduced exercise tolerance

• Dizziness, presyncope, or syncope

• Chest discomfort

• Features of heart failure

• Stroke, TIA, or systemic embolism

What are some potentially life threatening features AF can present with?

• Shock

• Syncope with severe / ongoing hypotension

• Myocardial ischaemia (chest pain)

• Severe heart failure with pulmonary oedema

When first assessing someone presenting with AF, what should you quickly determine?

Whether the AF is stable or unstable - if it is unstable the patient will need immediate treatment.

What does AF stability depend on?

Whether the patient is haemodynamically stable.

What are the signs that a patient has unstable AF?

• Shock (BP<90 systolic)

• Loss of consciousness/syncope

• Myocardial Ischaemia (chest pain or suggestive ECG changes)

• Heart Failure

Investigations for AF

• Manual pulse palpation

• 12 lead ECG to confirm

• 24hr ambulatory ECG monitoring if asymptomatic episodes are suspected / if symptomatic episodes happen less than 24hrs apart.

• Longer ambulatory monitoring may be required if symptomatic episodes are happening >24hrs apart.

• Blood tests

• Transthoracic echocardiography when indicated

• Chest X-ray when indicated

• Transoesophageal echocardiography if indicated

What is a 12 lead ECG used for when investigating AF?

• To confirm the diagnosis

• Assess ventricular rate and QRS width

• Look for conduction diseases

• Look for ischaemic changes and possible pre-excitation

What blood tests might be useful when investigating AF?

• FBC

• Renal function / electrolytes

• Liver tests

• Thyroid function if appropriate

• Glucose / HbA1c if appropriate

• Magnesium if indicated

• CRP if indicated

• Troponin if indicated

What is a transthoracic echocardiography used for when investigating AF?

Offer only when:

• A baseline echo is important for long-term management

• Rhythm control/cardioversion is being considered

• Structural or functional heart disease is suspected

• Refinement of clinical risk assessment is needed

What is a chest X-ray used for when investigating AF?

Offer only when there is suspected:

• Heart failure

• Infection

• Lung disease

What is a transoesophageal echocardiography used for when investigating AF?

Offer only when:

• Transthoracic imaging is inadequate for a management decision.

• Part of a specialist strategy to exclude left atrial thrombus before early cardioversion.

How is unstable AF managed?

• Call for expert help

• Monitor ECG, BP, and oxygen sats

• Obtain IV access

• Record a 12 lead ECG if this does not delay treatment.

• Give oxygen if hypoxic (<94%)

• Deliver synchronised electrical cardioversion, with sedation and anaesthesia if conscious and it does not cause an unsafe delay.

• If cardioversion is unsuccessful, follow the current tachyarrhythmia algorithm and seek expert advice.

• Treat reversible causes and assess anticoagulation as soon as possible - do not delay emergency cardioversion though.

How is stable AF managed?

• Treat the reversible cause

• Rate control is then the first line strategy

• Offer rhythm control when symptoms remain after rate control

• Assess stroke risk and consider anticoagulation if appropriate

• Long term review

• There are certain circumstances where this treatment algorithm does not apply.

When is rate control not the first line strategy?

• HF is probably primarily caused by AF

• AF is new onset

• Patient also has an atrial flutter which is suitable for an ablation strategy

• Rhythm control is preferable after discussion

In what situations does the usual treatment algorithm for stable AF ot apply?

• Pre-excited AF

• Acute ischaemic stroke / TIA

• Acute coronary syndrome / PCI

• Pregnancy

• Hyperthyroidism or sepsis associated AF

• Post ablation or apparent resolution

What is pre-excited AF?

An irregular broad-complex tachycardia caused by AF conducting through an accessory pathway. E.g. patient with Wolf-Parkinson-White syndrome and AF.

What should you do if a patient has pre-excited AF?

• Do not give AV-node-blocking drugs such as beta-blockers, verapamil, diltiazem, digoxin or adenosine.

• Seek urgent expert help

• RCUK lists procainamide or cardioversion.

What should you do if a patient has AF and an acute ischaemic stroke / TIA?

Follow the stroke pathway.

What should you do if a patient has acute coronary syndrome / PCI and AF?

• Combined antiplatelet and anticoagulant treatment increases bleeding risk.

• Use the relevant cardiology pathway and minimise combination duration where possible.

What should you do if a patient is pregnant and has AF?

• DOACs and warfarin are generally unsuitable in pregnancy.

• Obtain urgent specialist obstetric/cardiology/haematology advice.

What should you do if a patient has hyperthyroidism and AF?

• Treat the precipitant.

• Do not assume stroke risk disappears when the trigger resolves.

• Reassess for ongoing AF and anticoagulation.

What should you do if a patient has sepsis associated AF?

• Treat the precipitant.

• Do not assume stroke risk disappears when the trigger resolves.

• Reassess for ongoing AF and anticoagulation.

What should you do if the patient is post-ablation and/or there is apparent resolution of the AF?

• Do not stop anticoagulation solely because sinus rhythm is restored or AF is no longer detected.

• Reassess CHA₂DS₂-VASc and bleeding risk.

What are the different drugs used for rate control?

• Standard beta-blocker (not sotalol) is first line

• Rate-limiting calcium channel blocker

• Digoxin

• Combination treatment

• Amiodarone (potassium channel blocker) - not for long term use

When is a standard beta-blocker not recommended for stable AF?

Avoid / cautiously use when the patient has:

• Acute decompensated heart failure

• Marked bradycardia

• Advanced AV block

• Bronchospasm

Indication and cautions for rate-limiting calcium channel blockers for patients with AF

• Diltiazem or verapamil may be used when appropriate.

• Avoid if the patient has left ventricular systolic dysfunction or acute decompensated heart failure.

• Do not combine verapamil with a beta-blocker.

Indication and cautions for digoxin for patients with AF

• Consider as monotherapy for non-paroxysmal AF when the person does little or no physical exercise, or when other rate-limiting drugs are ruled out.

• Less effective during exertion

• Dose according to renal function

• Check interactions / toxicity

Indication and cautions for combination treatment for patients with AF

• Consider two drugs when symptoms persist because of poor ventricular rate control.

• Monitor for bradycardia, hypotension and AV block.

• Obtain specialist advice where needed.

What are the different rhythm control methods?

• Synchronised electrical cardioversion

• Pharmacological cardioversion

• Rhythm control drugs

• Catheter ablation (pacing may also be an option)

What factors affect the preferred method of rhythm control?

• Onset and duration of AF

• Symptoms

• Structural heart disease

• Heart failure

• Comorbidity

• Treatment risks

• Patient preference

What is the cardioversion pathway?

• Immediate synchronised electrical cardioversion if the patient has unstable AF

• Onset clearly < 48 hrs - electrical/pharmacological cardioversion may be considered according to clinical context + specialist expertise.

• Onset > 48 hrs or uncertain - If long term rhythm control is planned, delay electric cardioversion (not pharmacological) until anticoagulation therapy has been maintained for >3 weeks.

After cardioversion, how is the patient managed?

• Continue anticoagulation for at least 4 weeks when indicated.

• Continue anticoagulation long term when indicated by stroke-risk assessment, irrespective of apparent maintenance of sinus rhythm.

When is rhythm control indicated?

When symptoms persist after heart rate has been controlled, or rate-control was not successful.

When is rate control for patients with AF considered successful?

• Strict control - resting heart rate of ≤ 80 bpm.

• Lenient control - resting heart rate of ≤110 bpm if symptomless and left ventricular systolic function remains normal.

When is cardioversion preferred to long term rhythm control?

• Patient has unstable AF.

• Patient has new-onset stable AF, and it is clinically appropriate.

What drugs are used for long-term rhythm control?

• Standard beta-blocker is typically first line

• Flecainide or Propafenone (cardiac sodium channel blocker)

• Dronedarone (multi-channel blocker)

• Amiodarone (potassium channel blocker)

When is dronedarone indicated for rhythm control?

• It is second line (beta-blockers are first)

• Not used in unstable of severe heart failure

When is Flecainide or Propafenone indicated for rhythm control?

May be considered when there is no known ischaemic or heart disease.

When is Amioderone indicated for rhythm control?

When left ventricular impairment or heart failure makes other options unsuitable, but long-term toxicity and interactions require monitoring.

When is catheter ablation offered?

• May be considered in patients with symptomatic paroxysmal / persistent AF when drug treatment is unsuccessful, unsuitable or not tolerated.

• Shared decision making should cover recurrence (20-40%) and procedural risks.

• AVN ablation with pacing is a specialist option for refractory symptoms and uncontrolled ventricular rate.

How is stroke risk assessed?

CHA₂DS₂-VASc

When is stroke risk assessed in AF patients?

• In all patients diagnosed with AF

• It is reassessed when clinical circumstances change, and at review.

Why is anticoagulation important for AF patients?

They are at increased risk of strokes as the uncoordinated contractions within the atria can result in blood clot formation:

• 20–30% of all strokes occur in people with atrial fibrillation.

• Patients with AF have a 142% increased risk of any stroke and a 133% greater risk of ischemic stroke compared to individuals without AF.

• Stroke is more severe and debilitating in patients with AF than among those who do not have AF.

CHA₂DS₂-VASc

A scoring tool to assess stroke risk.

Results:

• 0 - do not offer stroke-prevention anticoagulation

• 1:

  • Men - Consider anticoagulation, taking bleeding risk and preferences into account.

  • Women (1 is from sex alone) - do not offer stroke-prevention anticoagulation.

• 2 or more - Offer anticoagulation, taking bleeding risk and preferences into account.

When reviewing anticoagulation, how is bleeding risk assessed?

ORBIT

ORBIT score

A scoring tool to assess bleeding risk. Its purpose is to support discussion, monitoring and modification of bleeding risks; a high score is therefore not an automatic reason to withhold anticoagulation.

Alongside assessing bleeding risk with ORBIT, what other actions should be taken when considering prescribing anticoagulation to patients with AF?

Offer monitoring and support to modify risk factors for bleeding, including:

• Controlling hypertension.

• Review concurrent antiplatelets, NSAIDs and interacting medicines.

• Address harmful alcohol use.

• Investigate and treat anaemia or thrombocytopenia.

• Improve time in therapeutic range for vitamin K antagonist treatment.

• Reduce avoidable falls risk and review adherence.

What are the different treatment options for anticoagulation?

• DOAC

• Vitamin K antagonist (typically warfarin)

• Antiplatelet therapy

• Left atrial appendage occlusion

When are DOACs indicated for patients with AF?

• If indicated after assessing stroke and bleeding risk, these are first line.

• Select according to:

  • renal function

  • Age

  • Weight

  • Interactions

  • Adherence

  • Dosing preference

  • Comorbidity

• Contraindications include:

  • Mechanical heart valves

  • Moderate to severe rheumatic mitral stenosis

  • etc.

When are vitamin K antagonists indicated for patients with AF?

When DOACS are contraindicated (second line). Monitor INR and time in therapeutic range.

When are antiplatelets indicated for patients with AF?

• These are NOT offered as a monotherapy for anticoagulation in patients with AF.

• Patients with AF may have them in addition to other anticoagulants if they are necessary to manage another condition.

When is left atrial appendage occlusion indicated for patients with AF?

Consider only when anticoagulation is contraindicated or not tolerated; specialist assessment is required.

Management of DOACs in patients with AF

• Calculate creatinine clearance rather than relying only on eGFR for dosing decisions.

• Use the licensed AF dose and apply dose-reduction criteria exactly.

• Check renal and liver function, FBC, weight, interactions and adherence at baseline and periodically.

• Review more frequently with frailty, renal impairment, intercurrent illness or increased bleeding risk.

• Provide counselling about adherence, missed doses, bleeding, procedures and when to seek help.

Long term review in patients with AF

• Review at least annually.

• Review after treatment changes.

• Review more frequently when clinically indicated.

• Review:

  • Symptoms

  • Ventricular rate

  • Rhythm strategy

  • Adherence

  • Stroke and bleeding risks

  • Renal function

  • Adverse effects

  • Comorbidities

What risk factors should be managed alongside other treatments for AF?

• Optimise management of:

  • BP

  • Diabetes

  • HF

  • IHD

  • Lipid management

• Support weight reduction when overweight / obese.

• Reduce alcohol intake and avoid binge drinking.

• Encourage regular moderate physical activity while avoiding extreme unaccustomed endurance exercise.

• Assess for obstructive sleep apnoea when clinically suspected.

• Support smoking cessation and medication adherence.

Summary of AF clinical decision pathway

Features of AF on an ECG

1. Rate = Tachycardic

2. Rhythm = irregularly irregular

3. Axis = Typically normal, although there usually is no clear isoelectric baseline

4. Wave components:

• 
  

  • P waves - absent. Instead there are chaotic fibrillatory waves.

  • QRS complexes - narrow (normal), variable R-R intervals.

1. Summary: The ECG shows atrial fibrillation with a rapid ventricular response rate of about 132 bpm with a normal axis and QRS duration. R-R intervals are variable, showing an irregularly irregular rhythm. There is normal R progression, but no evidence of discrete P waves either normal or ectopic excluding sinus / atrial tachycardia.

Risk factors for AF

• Male sex

• Caucasian ethnicity

• Increasing age

• Alcohol

• Cigarette smoking

• Obesity

• Co-morbidities (e.g. chronic kidney disease and obstructive sleep apnoea)

AF diagnostic criteria

• A standard 12-lead ECG recording or a single-lead ECG recording of ≥30 seconds showing a heart rhythm of no discernible repeating P-waves AND

• Irregular RR intervals

Possible differential diagnoses in the context of suspected AF include:

• Other supraventricular tachycardias: atrial flutter, atrial extrasystoles, multifocal atrial tachycardia, sinus tachycardia

• Ventricular ectopics