Atrial Fibrillation

I48.0-I48.4/I48.9

• Medicine treatment

Acute onset (< 48 hours)

Assess clinically, e.g. heart failure, mitral stenosis, thyrotoxicosis, hypertension, age and other medical conditions.

Consider anticoagulation with warfarin (see table below on CHA₂DS₂-VASc Score).

Synchronised direct current (DC) cardioversion is occasionally necessary in haemodynamic instability.

Non-acute/chronic (> 48 hours)

As above, but not immediate DC cardioversion, unless there is haemodynamic instability.

MEDICINE TREATMENT

The main aims of therapy for patients with atrial fibrillation should be:

1. Reduction of stroke and systemic embolic risk.
2. Rate control.
3. Relief of symptoms attributed to the atrial fibrillation.

Patients <65 years of age with no heart diseases or other risk factors may be managed with aspirin alone.

A simple scoring system allows calculation of risk of stroke in patients with non-valvar atrial fibrillation.

CHA₂DS₂-VASc Score:

Source: Lip GY, Nieuwlaat R, Pisters R, Lane DA, Crijns HJ. Refining clinical risk stratification for predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based approach: the euro heart survey on atrial fibrillation.Chest. 2010 Feb;137(2):263-72. http://www.ncbi.nlm.nih.gov/pubmed/19762550

• When the score is ≥2, use warfarin or equivalent. The higher the score the greater the risk of stroke and therefore the more compelling the use of effective anticoagulation.
• Note: This score has been developed on patients with non-valvular atrial fibrillation and may not be applicable to patients with atrial fibrillation and rheumatic mitral valve disease. Anticoagulation has not been tested in this population but most authorities favour anticoagulation.

Initial therapy aimed at stroke reduction

Anticoagulate with warfarin:

• Warfarin, oral, 5 mg daily.
  • INR should be done after 48 hours, then every 1 to 2 days until within the therapeutic range of 2 to 3 (refer to initiation dosing tables in WARFARIN, oral).
  • Adjust dose to keep INR within therapeutic range (refer to Maintenance dosing tables in WARFARIN, oral).

For therapy aimed at rate control

• Atenolol, oral, 50–100 mg daily.
  • Contraindicated in asthmatics, heart failure.

OR

If in CCF: (I50.0)

• Carvedilol, oral. See: Congestive Cardiac Failure (CCF).

AND

If control not adequate add:

• Digoxin, oral, 0.125 mg daily, adjust according to rate response and trough plasma level
  • Digoxin trough plasma levels (before the morning dose) should be maintained between 0.6-1 nmol/L.
  • Patients at high risk of digoxin toxicity: the elderly, patients with renal dysfunction, hypokalaemia, and patients with lean body mass.

LoEII [39]

If β-blockers are contra-indicated, e.g. asthma or severe peripheral vascular disease:

• Verapamil, oral, 40–120 mg 8 hourly.
  • Titrate against ventricular rate (verapamil is negatively inotropic, therefore avoid in heart failure due to LV dysfunction).

LoEIII [40]

If not controlled on these agents, refer to specialist for consideration of alternative therapy, e.g. amiodarone or atrioventricular node ablation and pacemaker insertion.

DC cardioversion in selected cases, after 4 weeks effective warfarin anticoagulation.

Long-term therapy

Continue warfarin anticoagulation long-term, unless contra-indicated:

• Warfarin, oral, 5 mg daily.
  • Control with INR to therapeutic range:
    • INR between 2–3 and patient stable: monitor every 3 months.
    • INR <1.5 or >3.5: monitor monthly.

Caution

Warfarin use requires regular INR monitoring and dose adjustment according to measured INR.

For rate control:

• Atenolol, oral, 50–100 mg daily.
  • Contraindicated in asthmatics, heart failure.

If in CCF: (I50.0)

• Carvedilol, oral. See: Congestive cardiac failure.

AND

If control not adequate add:

• Digoxin, oral, start at 0.125 mg daily and adjust according to rate response and trough plasma level.
  • In patients with impaired renal function (eGFR <60 mL/minute), consider 0.125 mg daily and adjust according to trough level monitoring.
  • In all patients, digoxin trough level monitoring is required at all doses.

LoEII [41]

If β-blockers are contra-indicated, e.g. asthma or severe peripheral vascular disease:

• Verapamil, oral, 40–120 mg 8 hourly.
  • Titrate against ventricular rate (verapamil is negatively inotropic, avoid in heart failure due to left ventricular dysfunction).

LoEIII [42]

If not controlled on these agents, refer to specialist for consideration of alternative therapy.

Prevention of recurrent paroxysmal atrial fibrillation:
Note: The risk of thromboembolic complications and stroke is similar to that of patients with persistent or paroxysmal atrial fibrillation and similar recommendations as to anticoagulation apply.
Only in patients with severe symptoms despite the above measures:

• Amiodarone, oral, 200 mg 8 hourly for 1 week. Specialist initiated.
  • Followed by 200 mg 12 hourly for one week.
  • Thereafter, 200 mg daily.

LoEI [43]

Precautions:

• If on warfarin, halve the dose of warfarin and monitor INR closely, until INR is stable.
• Avoid concomitant digoxin.
• Monitor thyroid function every 6 months as thyroid abnormalities may develop.
• Ophthalmological examination every 6 months.

For management of pregnant women with valvular disease and atrial fibrillation, see Heart disease in pregnancy.