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Atrial Fibrillation

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Overview

Atrial fibrillation (AF) is the most common arrhythmia. It is a type of supraventricular arrhythmia leading to uncoordinated electrical conduction and ineffective atrial contraction. An ECG shows:

  • An irregularly irregular pulse
  • Absence of P waves

The correct management of AF is essential as it can lead to serious complications including:

  • Stroke – stagnation of blood can lead to the formation of a thrombus, which can embolise and lead to a stroke
  • Heart failure – due to reduced cardiac output and increased workload on the heart

Classification

AF is classified according to the pattern of episodes:

  • Paroxysmal AF:
    • Episodes lasting >30 seconds but <7 days (often <48 hours) which are self-terminating and recurrent
  • Persistent AF:
    • Episodes lasting >7 days or <7 days but requiring pharmacological or electrical cardioversion. The 7-day threshold is used because AF is unlikely to spontaneously terminate after this time. 
  • Permanent AF:
    • AF that fails to terminate with cardioversion, AF that relapses within 24 hours, or longstanding AF (usually >1 year) in which cardioversion has not been indicated or attempted (also known as accepted permanent AF).

Epidemiology

  • AF is the most common sustained arrhythmia
  • Prevalence is higher in men than in women

Causes

Acute AF

Chronic AF

Presentation

The hallmark feature of AF is an irregularly irregular pulse. Some patients may be asymptomatic. Other features include:

Some patients may present with haemodynamic instability. These patients need urgent emergency care:

  • Acute heart failure:
  • Cardiogenic shock:
    • Tachycardia (>150 bpm) and hypotension (systolic blood pressure <90 mmHg)
  • Syncope/pre-syncope
  • Cardiac chest pain and shortness of breath

Investigations

Overview

  • ECG:
    • Diagnoses AF and shows an irregularly irregular rhythm with absent P waves
  • Holter (ambulatory ECG) monitoring:
    • If the ECG fails to show AF and paroxysmal AF is suspected

Figure 1: An ECG showing atrial fibrillation

Other investigations to consider are to identify underlying causes:

  • Full blood count (FBC):
    • Identifies any underlying triggers such as anaemia/infection
  • Urea and electrolytes (U&Es):
    • To screen for electrolyte imbalances
    • To screen for renal dysfunction which may alter management if present
  • Thyroid function tests (TFTs):
    • To exclude thyrotoxicosis, which may be a trigger
  • Echocardiography:
    • To screen for underlying heart disease
    • Also performed if the CHA2DS2-VASc score suggests that anticoagulation is not needed. Any patient with structural heart disease must be anticoagulated, regardless of the CHA2DS2-VASc score

Rate and Rhythm Control

Rate control

Rate control reduces the heart rate at rest and on exertion. This reduces the severity of symptoms, but does not terminate AF:

  • 1st-line: monotherapy with a beta-blocker (except sotalol) orrate-limiting calcium channel blockers (CCBs, verapamil or diltiazem)
    • For instance, people with asthma cannot take beta-blockers, therefore rate-limiting are more appropriate
  • 2nd-line: digoxin
    • Considered in patients who do no or very little exercise or if first-line options are ineffective/contraindicated
    • Digoxin is less effective with exertion

Rhythm control

Rhythm control aims to restore normal sinus rhythm. This can be done via:

  • Direct current (DC) cardioversion:
    • Using electrical stimulation to restore sinus rhythm
    • Pharmacological cardioversion or beta-blockers can be used to maintain sinus rhythm
  • Pharmacological cardioversion:
    • If no structural heart disease present: amiodarone or flecainide
    • If structural heart disease present: amiodarone
      • Flecainide is contraindicated in those with structural or ischaemic heart disease

Rhythm control is performed if patients have had a short duration of symptoms (<48 hours) or have been anticoagulated for at least 3 weeks. This is because restoring sinus rhythm risks dislodging a blood clot formed in the atrium and subsequent stroke.

Anticoagulation

CHA2DS2VASc score

All patients with AF, including those not currently in AF, should have the need for anticoagulation considered due to the risk of stroke. NICE recommends using the CHA2DS2VASc score:

Stroke risk factorScore
C: Congestive heart failure1
H: Hypertension1
A2: Age ≥752
D: Diabetes mellitus1
S2: Stroke2
V: Vascular disease (prior myocardial infarction, peripheral arterial disease, atherosclerosis)1
A: Age 65-741
S: Sex (if female)1

Table 1: The CHA2DS2-VASc score

The CHA2DS2-VASc score is used to assess the risk of stroke in any patient with AF. Management is guided by the score:

  • 0 – no treatment
  • 1:
    • If male: consider treatment
    • If female: no treatment (being female gives a score of 1 on its own)
  • 2 or more – offer anticoagulation

If the score suggests no anticoagulation is needed, a transthoracic echocardiogram must be performed. If there are signs of valvular/structural heart disease, patients should be anticoagulated regardless of the CHA2DS2-VASc score.

ORBIT score

The ORBIT score is used to assess the risk of bleeds in patients being considered for anticoagulation. NICE recommends that we do not withhold anticoagulation solely on the basis of a person’s age or fall risk. The ORBIT score alone should not exclude anticoagulant treatment. The bleeding risk can vary and requires regular re-assessment.

Bleeding risk factorScore
Haemoglobin:Male: <130g/L or haematocrit <40%Female: <120g/L or haematocrit <36%2
Age >74 years1
Bleeding history (gastrointestinal bleeding, intracranial bleeding, haemorrhagic stroke): 2
GFR <60mL/min/1.73m21
Treatment with antiplatelets1

Table 2: The ORBIT score

Anticoagulant drugs

The following drugs are used if anticoagulation is indicated in a patient with AF:

  • 1st-line: direct oral anticoagulants (DOACs):
    • Apixaban, rivaroxaban, edoxaban, dabigatran
  • 2nd-line: warfarin if a DOAC is not tolerated or contraindicated

Aspirin is not used in reducing the risk of stroke in patients with AF.

Management

Overview

The key aspects of management include:

  • Initial assessment and treatment of haemodynamic instability
  • Management of complications including stroke
  • Management of non-life-threatening AF – including rate and rhythm control
  • Management of the risk of complications – including anticoagulation

AF with haemodynamic instability

  • ABCDE approach
  • Immediate direct current (DC) cardioversion

Management of complications

  • ABCDE approach
  • If a stroke occurs, patients are given aspirin for 2 weeks (the same as standard management of stroke) followed by anticoagulation with a direct oral anticoagulant (DOAC) or warfarin as soon as possible.

Acute AF, onset <48 hours

If patients present acutely with AF and its onset is less than 48 hours, either rate or rhythm control is offered. Management is as follows:

  • Initial anticoagulation:
    • In the absence of no contraindications and the patient is not taking anticoagulants:  give heparin
    • This is continued until decisions about long-term anticoagulation are made 
  • Pharmacological or electrical cardioversion depending on clinical circumstances and resources:
    • Pharmacological cardioversion:
      • If no structural/ischaemic heart disease: flecainide or amiodarone
      • If structural/ischaemic heart disease present: amiodarone
  • Long-term anticoagulation:
    • Oral anticoagulation is given if the CHA2DS2-VASc score indicates it or there are risk factors for AF recurrence (e.g. failed cardioversion, structural heart disease, prolonged AF, or previous occurrences)

Acute AF, onset >48 hours or unknown

If patients present acutely with AF and its onset is >48 hours, immediate rate control is offered followed by delayed rhythm control. Management is as follows:

  • Rate control and a minimum of 3 weeks anticoagulation first:
    • This is to reduce the risk of clots dislodging and causing a stroke following cardioversion
    • A transoesophageal echocardiogram can be performed to exclude a left atrial appendage thrombus. If a thrombus is ruled out, then patients can be given heparin and cardioverted immediately, followed by giving oral anticoagulation if the CHA2DS2-VASc score indicates it or there are risk factors for AF recurrence (e.g. failed cardioversion, structural heart disease, prolonged AF, or previous occurrences)
  • Followed by delayed rhythm control:
    • Electrical cardioversion is preferred in this scenario rather than pharmacological cardioversion
    • Consider amiodarone starting 4 weeks before and up to 12 months after electrical cardioversion
  • Followed by anticoagulation:
    • This is continued for at least 4 weeks until decisions about long-term anticoagulation are made. 
    • Oral anticoagulation is given if the CHA2DS2-VASc score indicates it or there are risk factors for AF recurrence (e.g. failed cardioversion, structural heart disease, prolonged AF, or previous occurrences)

Catheter ablation

If drug treatment is unsuccessful, unsuitable, or not tolerated in AF, catheter ablation may be considered. Ablation may control rhythm but does not decrease stroke risk. Therefore, anticoagulation must still be given as per the CHA2DS2-VASc score.

Monitoring

Patients are usually followed-up in primary care where:

  • Management plans are put in place
  • Adherence of the patient is checked, and their concerns addressed
  • Treatment is changed if needed

Patient Advice

  • Patients should undertake regular exercise but avoid excessive endurance exercise e.g. marathons, especially if they are >50 years old
  • Patients should lose weight/stop smoking where appropriate as this reduces their risk of developing cardiovascular disease
  • Patients should reduce alcohol intake as this can contribute to arrhythmia

Complications

  • Stroke
  • Heart failure
  • Myocardial infarction

Prognosis

  • People with AF have 2 times the mortality and 5 times the stroke risk than those without
  • The prognosis varies depending on the underlying conditions present

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