Atrial Fibrillation (AF)
AF is the most common sustained arrhythmia affecting approximately 1-2% of the population. It is associated with increased cardiovascular morbidity and mortality and preventable stroke. With the increasing age of the population, AF is becoming more prevalent in the community.
There is no strong evidence to favour either a rate control or rhythm control strategy. This is partly because there is a reasonably high spontaneous reversion rate – around one third in the first 6 hours, and the adverse event rate is very low making it hard to differentiate any strategy on the basis of safety.
In otherwise healthy patients with acute AF, a strategy to return them to sinus rhythm as soon as possible seems reasonable. In patients with an unknown duration of AF, or significant cardiac or other illness disease, emphasis should be on rate control.
1. First detected episode
Paroxysmal AF (self-terminating, usually <24 hours)
Persistent (sustained >7days)
An assessment of haemodynamic instability should be made first. Parameters suggesting instability include:
- Decreased LOC
- Chest pain
- Shortness of breath (due to heart failure)
- Systolic of less than 90mmHg (or 30-40mm less than the patient’s usual SBP)
Patients assessed as unstable require immediate cardioversion to prevent further deterioration to cardiac arrest. This is uncommon in the setting of uncomplicated AF. The need for urgent cardioversion should also be anticipated in patients where decompensation is thought likely. The parameters above are a guide only. For example a patient who appears well and has atypical chest pain and has no shortness of breath will not get cardioverted, whereas a patient who is diaphoretic, appears unwell and has a systolic of 80 should get cardioverted urgently.
In stable patients, evaluation involves history, examination and ECG. Blood tests including renal function, full blood count and magnesium levels are routine. Hepatic and thyroid function should also be considered. Coagulation studies should be sent in patients where anticoagulation is likely to be commenced, or in patients already on warfarin. Transthoracic echo is ideal, if available.
Objectives in the management of AF are:
- Identify and treat associated or causative factors which may abort the arrhythmia
- fluid resuscitation in dry patients
- temperature control and antibiotics where there is an infection
- electrolyte deficiencies, particulalry magnesium and potassium
- Decide on rate control or rhythm control
- Prevent thromboembolism (balancing the risk of stroke against risk of bleeding from anticoagulation) - CHADS2, HASBLED.
Reversible causes of atrial fibrillation
- Cardiac, pulmonary, oesophageal, or general surgery
Inflammatory atrial disease
Atrial pressure elevation
- Pulmonary embolism
Atrial fibrillation with associated heart disease
Atrial pressure elevation
- Hypertension (particularly when left ventricular hypertrophy is present)
- Valvular heart disease (mitral or tricuspid valve disease)
- Myocardial disease leading to systolic or diastolic dysfunction (ischaemic cardiomyopathy, dilated cardiomyopathy, hypertrophic cardiomyopathy)
- Intracardiac tumours or thrombi
- Coronary artery disease
Congenital heart disease
- Atrial septal defect
Infiltrative atrial disease
- Age-induced atrial fibrotic changes
- Endomyocardial fibrosis
- Primary or metastatic disease in or adjacent to the atrial wall
- Enhanced automaticity (focal atrial fibrillation)
- Conduction abnormality (re-entry)
Atrial fibrillation without associated heart disease
- Idiopathic “lone” atrial fibrillation
Atrial fibrillation associated with medical conditions
- Sleep apnoea
- Subarachnoid haemorrhage
- Major ischaemic stroke
Familial atrial fibrillation
While rate versus rhythm contol is a key issue in the management of AF, the AFFIRM study showed no statistically significant difference in mortality or in quality of life with either management. Most patients require control of heart rate for symptomatic relief and to prevent tachycardia-induced cardiomyopathy.
In an otherwise healthy person (stable) with AF for less than 48hrs, chemical cardioversion is appropriate.
Cardioversion (electrical or chemical) to achieve rhythm control is not recommended where onset of AF is thought to be more than 48 hours earlier (unless unstable). There is no clear evidence for this time, however it is widely accepted and stated in guidelines.
The most potent rhythm control agent is DC cardioversion, with success rates well above 90% in published trials. These also demonstrate
- positioning of the pads matters: anterior and posterior is better than anterior and lateral
- bi-phasic waveform is better than mono-phasic
- the optimum initial energy for bi-phasic is 100 Joules.
Pharmacological cardioversion effectively restores sinus rhythm in approximately 50% of patients with recent-onset atrial fibrillation.
For a patient with atrial fibrillation who has normal left ventricular function and no coronary disease, flecainide is preferred by cardiologists. In the ED we will rarely know a patent has normal ventricular function and coronary arteries. For this reason Amiodarone is the preferred ED option for chemical cardioversion.
Patients with duration of AF of over 48hrs and/or patients with chronic cardiac complaints as per CHADS2 should have rate control and anticoagulation started.
- Calcium channel blockers (CCB) and beta blockers are both effective agents to reduce the ventricular rate. Neither increases the likelihood of conversion to sinus rhythm. The most studied intravenous calcium channel blocker – Diltiazem – is not available in Australia and with limited data on verapamil, beta blockers are probably the better option for rapid IV rate control. There is little evidence favouring one agent over another – take your pick. However, there is rarely a real urgency to control rate, so oral therapy with either diltiazem or a beta blocker is a reasonable approach. Often this will depend on local cardiologist preference.
- Digoxin does have rate control properties, but is slower to work than calcium channel blockers and beta blockers. However it does not have the negative inotropy of the other agents so is a reasonable and safe choice in patients with poor LV function or who are compromised for other reasons such as sepsis. It has no rhythm control properties.
Anti-arrhythmic drugs only have a 40-60% success rate for maintaining sinus rhythm at 1 year and have significant side effects. Older patients >65 years with recurrent persistent AF at high risk of stroke (CHADS2 score of 1 or more) have similar out comes (stroke or mortality) with either rate or rhythm control and a trend towards fewer hospitalisations for those rate controlled. Rate control is more suitable for older patients with persistent or permanent AF whereas young patients with highly symptomatic paroxysmal AF may require rhythm control.
- Metoprolol 25-100mg bd PO
- Metoprolol 5mg IV (1-2mg per minute) repeated at 5-minute intervals if necessary, up to a total 15mg (usually total doses of around 5mg are required)
- Atenolol 25-100mg daily PO (IV not available)
Calcium Channel Blockers
- Verapamil SR 160-480mg daily PO
- Verapamil IV 1-2mg every 5 minutes up to a max 15mg (due to varying IV dose suggestions discuss with Senior ED or Cardiology)
- Diltiazem CR 180-360mg daily PO
Beta blockers and Calcium channel blockers control both exertional and resting heart rate
- Digoxin loading: Digoxin 250-500mcg IV or oral initial dose, then followed by further doses of 125-250mcg q6-8h to a maximum of 1mg or until control achieved (inpatient regime only).
- Maintenance therapy: digoxin 62.5-250mcg PO in patients who are elderly, sedentary or those with heart failure. Adjust dose accordingly to renal function (eGFR) and age.
The decision to attempt cardioversion and maintain sinus rhythm depends on the long term frequency and hazards of AF and risks of cardioversion and therapy. Cardioversion can be attempted using anti-arrhythmic medication or by electrical cardioversion.
Stroke may occur at the time of cardioversion because of the expulsion of an atrial thrombus and up to 4-6 weeks after because of atrial stunning. It is generally regarded as safe if it is certain the episode has lasted less than 48 hours (limited hard evidence). The options are to anticoagulate for at least 3 weeks prior and 4-6 weeks post, or a pre-procedure TOE to exclude the presence of LA/LAA thrombus.
- 150-300mg IV infusion over 20 minutes - 2 hours
- Or 200-400mg po tds for 1 week, then taper dose
- 2mg/kg up to 150mg IV infusion over 30 minutes
- Or 50-100mg po 2-3 times/day
- Can be used as a ‘pill in the pocket’ for infrequent highly symptomatic AF
- Possibility of accelerating ventricular rate so consider pre-treatment with AV nodal blocking drug e.g. Digoxin, beta blocker, verapamil, diltiazem
- Fleicanide is contraindicated in structural heart disease
Prevention of thromboembolism
AF predisposes to the formation of blood clots within the left atrium and left atrial appendage which may embolise to the systemic circulation. Consequently AF is an independent risk factor for cardio-embolic ischaemic stroke. These strokes are typically large and associated with high early mortality. Optimal thromboprophylaxis is important but requires individual assessment.
Use of antithrombotic prophylaxis depends on the patient’s long term risk of ischaemic stroke (estimated by the CHADS2 score) and the benefits and risks of long term anticoagulation including major bleeding (this can be estimated using tools such as HASBLED). Although stroke risk is highest in those over 85 years, anticoagulation is often not recommended in this age group due to increased falls risk, difficulties with medication compliance, access to INR testing and drug interactions.
Oral anticoagulation is recommended for people at moderate to high risk of stroke (CHADS2 score ≥1) unless contraindicated or annual major bleeding risk >3%. Aspirin is recommended in patients with CHADS2 score of 0, or if anticoagulation contraindicated. Stroke risk should be re-assessed yearly.
Anticoagulation medication includes warfarin and the novel oral anti-cogulants (NOACs Dabigatran, Rivaroxaban and Apixaban). The National Prescribing Service only recommends NOACs as suitable for stroke prevention in non-valvular AF. Valvular AF carries a much higher risk of stroke and there is insufficient evidence of NOAC efficacy in this group of patients. NOACs are contraindicated in people with severe renal failure.
Radiofrequency ablation (RFA) is an increasingly used therapeutic strategy for the management of AF. The procedure involves application of radiofrequency energy to electrically isolate the pulmonary veins, and/or to ablate identified trigger areas, in an attempt to cure the patient of AF.
The National Heart Foundation of Australia produced a consensus statement in January 2013. It recommends the primary indication being the presence of symptomatic AF that is refractory or intolerant of class 1 or class 3 antiarrhythmic medications. Best results have been seen in younger patients with paroxysmal AF, no structural heart disease and smaller atria. Patients with persistent AF or CHADS2 score ≥ 2 require anticoagulation for at least 3 weeks prior to RFA as well as a transoeophageal echo to eclude atrial thrombus. Anticoagulation is continued for at least 1-3 months post procedure but not recommended to be ceased in patients with a CHADS2 score ≥ 2.
This is a tool to stratify the risk of stroke in patients with non-valvular AF to assist in the need for treatment with anti-coagulation.
CHADS2 Score - (click here for online calculator)
|Congestive heart failure||1 point|
|Age > 75 years||1 point|
|Stroke / TIA||2 points|
Note: Low risk = 0 Points, Moderate Risk = 1 Point, High Risk = 2 Points
Oral anticoagulation is recommended for people with moderate to high risk of stroke unless contraindicated.
The CHA2DS2VASc score, introduced by the European Society of Cardiology provides a more comprehensive stroke risk assessment extending the score with points allotted for female sex, vascular disease and age 65-74yrs. Click here for online calculator.
Pisters R, Lane DA, Nieuwlaat R, de Vos CB, Crijns HJ, Lip GY. A novel user-friendly score (HAS-BLED) to assess 1-year risk of major bleeding in patients with atrial fibrillation: the Euro Heart Survey. Chest. 2010 Nov; 138(5):1093-100. Epub 2010 Mar 18. PubMed PMID: 20299623.
Abnormal liver or kidney function
1 point each
Elderly (e.g. >65 years)
Drugs or alcohol
1 point each
>3 = high risk
Using this tool you can identify correctable risk factors for bleeding and people who need increased clinical monitoring. >3 equates to high risk.
- Hypertension = systolic blood pressure >160 mmHg
- Abnormal renal function = dialysis / renal transplantation / serum creatinine ≥200 micromol/L
- Abnormal liver function = chronic hepatic dysfunction (e.g. cirrhosis) or biochemical evidence of significant hepatic derangement (e.g. bilirubin 2 x upper limit of normal in association with AST / ALT / ALP 3 x upper limit normal etc.)
- Bleeding = history of intracranial bleeding, bleeding requiring hospitalization, haemoglobin decrease >20mg/mL, and/or transfusion.
- Drugs = concominant use of antiplatelet or non-steroidal anti-inflammatory drugs
Online calculator: This calculator gives you a point estimate of the risk of major bleeding for patients on anticoagulation. Compare this to the patient’s estimated risk of stroke using CHADS2-VASC to help determine the risk-benefit ratio of anticoagulation in atrial fibrillation care.
Further References and Resources
- Medi, C, Hankey, G, Freedman, S (2007) Atrial Fibrillation, Medical Journal of Australia, vol. 186, no. 4, p. 197-202
- Samardhi, H, Santos, M, Denman, R, Walters, D & Bett, N (2011) Current Management of Atrial Fibrillation, Australian Prescriber, 2011, vol. 34. p. 100-104.
- Wyse, D, Waldo, A, DiMarco, J, Domanski, M, Rosenberg, Y, Schron, E, Kellan, J, Greene, H, Mickel, M, Dalquist, J & Corley, S (2002) A Comparison of rate control and rhythm control in patients with atrial fibrillation (AFFIRM Study), The New England Journal of Medicine, December 2002, vol. 347,p. 1825-1833.
- Kirchhof P, Benussi S, et al. 2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS. Eur Heart J, 2016 (37): pp. 2893-2962.
- Acute Atrial Afibrillation Educational Resources - Dr Rod Bishop
- DC Cardioversion