Atrial Fibrillation/Flutter
Introduction
Atrial fibrillation and atrial flutter are 2 types of supraventricular tachycardia.
Atrial fibrillation (AF) is the most common sustained arrhythmia. It is characterised by disorganised atrial electrical activity and contraction. Depending on the rate of ventricular contraction AF is either “rate controlled” or associated with “rapid ventricular response”i.e. fast AF.
Atrial flutter is caused by a re-entry circuit within the right atrium. Ventricular rate is determined by the AV conduction ratio. The commonest AV ratio is 2:1, resulting in a ventricular rate of ~150 bpm. Atrial flutter is diagnosed when saw tooth pattern (flutter waves) are seen on ECG.
Complications of AF/Flutter include haemodynamic instability, cardiomyopathy, cardiac failure, and embolic events such as stroke due to thrombus formation secondary to disorganised atrial contraction.
Risk Factors for Developing Atrial Fibrillation
Cardiac
IHD
Valvular Disease
Pericarditis
Pre-excitation syndrome
Cardiomyopathy
Other
Increased incidence with age
Sepsis
PE
COPD
Obstructive sleep apnoea
Electrolyte derangement e.g hypokalaemia, hypomagnasaemia
Drugs/alcohol,
Thyrotoxicosis
Clinical Features
Symptoms
Palpitations
Dizzyness/Pre-syncope
Shortness of breath
Chest pain
Reduce exercise tolerance
Syncope/loss of consciousness
Fatigue
Symptoms associated with potential cause e.g. COPD, PE, hyperthyroidism
Signs
Irregularly irregular pulse
Tachycardia
Tachypnea
Signs of haemodynamic compromise e.g. pallor, cool to touch, hypotension, decreased conscious state
Confusion
Signs of cause e.g. sepsis, thyrotoxicosis
Signs of complications e.g. stroke/TIA, heart failure
Differential Diagnosis
Narrow Complex Arrhythmia
HR < 100 + Regular Narrow Complex
Sinus rhythm
Junctional rhythm
A Flutter with regular block e.g. 3:1
Mobitz II 2nd degree HB with regular block
CHB with junctional escape rhythm
HR < 100 + Irregular Narrow Complex
Sinus arrhythmia
Rate controlled Atrial Fibrillation
Atrial Flutter with variable penetrance
Type 1 2nd Degree HB (Wencebach)
Type 2 2nd Degree HB with variable block
HR > 100 + Regular Narrow Complex
Sinus Tachy
SVT i.e.Atrial tachycardia, Junctional tachycardia, Re-entry tachyarrhythmia e.g. WPW
Atrial Flutter with 2:1 or 1:1 block
HR > 100 + Irregular Narrow Complex
Atrial fibrillationwith RVR
Atrial flutter with variable penetrance
Atrial tachycardia with variable conduction
Mutifocal atrial tachycardia
Broad Complex Arrhythmia
HR < 100 + Regular Broad Complex
Sinus rhythm with aberrancy e.g. RBBB/LBBB
Slow A Flutter with aberrancy
Ventricular escape rhythm - HR < 40
Accelerated intra-ventricular rhythm - HR 40–110
HR < 100 + Irregular Broad Complex
Causes of irregular narrow complex with aberrancy
HR > 100 + Regular Broad Complex
Ventricular Tachycardia (VT) - rate > 110bpm
Sinus tachycardia with aberrancy
SVT with aberrancy
Accelerated intra-ventricular rhythm - HR 40–110
HR > 100 + Irregular Broad Complex
Polymorphic VT i.e. Torsades de Pointes
AF with aberrancy
AF with WPW
Clinical Investigations
Bedside
ECG
VBG - pH, electrolytes, lactate, O2, glucose level
MSU - ? underlying infection
Atrial Fibrillation
Irregularly irregular rhythm.
Rate = variable. Usually between 50-150 bpm
No P waves.
Absence of an isoelectric baseline.
Variable ventricular rate.
QRS complexes usually < 120 ms unless aberrancy
Atrial Flutter
Narrow complex tachycardia
Regular atrial activity at ~300 bpm
Ventricular rate is a fraction of the atrial rate e.g. 2:1 block = 150 bpm. 3:1 block = 100 bpm, 4:1 block = 75 bpm
Flutter waves (“saw-tooth” pattern)
best seen in leads II, III, aVF
Loss of the isoelectric baseline
Laboratory
FBC - ?raised inflamm markers, ? anaemia
U&E - ? evidence of dehydration/electrolyte derangement
Mg, Ca,
Troponin if concerned about myocardial ischaemia
CRP if concerned about infection
Other laboratory testing to be guided by most likely underlying aetiology
e.g. blood culture, D-Dimer, TFTs
Radiology
CXR – cardiomegaly, pulmonary oedema, pneumonia
ECHO
POCUS in ED by experieced operator if patient is unstable and concerned about acute pathology e.g. Massive PE, Cardiomyopathy, Pericardial effusion,
Departmental echo with cardiology assessing for valvular disease, chamber dilation, atrial and ventricular wall thickness and function, thrombus.
Other radiological investigations to be guided by most likely underlying cause if any.
Management & Disposition
When approaching any patient with atrial fibrillation there are a number of questions to ask.
Is the patient stable or unstable?
Is there an underlying treatable cause?
Is the atrial fibrillation new or old?
Rate control vs rhythm control?
Does the patient need to be anti-coagulated?
Initial Resuscitation
If haemodynamically unstable patient should be managed in resus area with full non invasive cardiac monitoring
Seek and treat any other causes of shock i.e. sepsis, hypovolaemia, PE, tamponade
If nil other cause of shock and patient is unstable patient should be urgently cardioverted with synchronised DC cardioversion.
Do not wait for anticoagulation in unstable patient
Specific Treatment
Acute atrial fibrillation without life‑threatening haemodynamic instability
Rate control if onset > 48 hours or if unsure.
Beta blockers e.g. metoprolol or Digoxin
Delayed cardioversion may be offered by cardiology as an out patient following several weeks. Doesn’t happen in ED
Rate or rhythm control if the onset < 48hours
Pharmacological cardioversion = Flecanide or amiodarone
Electrical cardioversion = Synchronised DC shock.
Cardioversion should only be performed in people who have a structurally normal heart. i.e. the young patient or patient with recent normal echo.
Assessment of stroke and bleeding risk in persistent AF or AF of unknown duration.
Use the CHA2DS2-VASc stroke risk score to assess stroke risk
Use the HAS-BLED score to assess the risk of bleeding in people who are starting or have started anticoagulation
Symptomatic Treatment
Treat any underlying cause e.g. IV fluids if concerned re hypovolaemia or dehydration
O2 to keep sats > 92%
IV anlagesia/anti-emetic as required
Disposition
Incidental finding of rate controlled AF does not need an acute hospital admission in an otherwise stable patient
These patients can be referred directed to their GP for consideration of anticoagulation +/- referral to cardiology OPD for echo and work up
Patients with rapid or symptomatic AF generally require admission under the medical or cardiology team for a period of cardiac monitoring to assess for response to treatment.
Unstable patients, those who require urgent cardioversion or those with significant underlying causative pathology may need to be admitted to a CCU or HDU environment
References
Burns A. Atrial Fibrillation[Internet]. Australia: Life in the fast lane; 2020 [cited 2020 Nov 4]. Available from: https://litfl.com/atrial-fibrillation-ecg-library/
Rosenthal L, McManus DD, Sardana M. Atrial Fibrillation[Internet]. Medscape; updated 2019 [cited 2020 Nov 3]. Available from: https://emedicine.medscape.com/article/151066-overview
Pisters R et al. 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
Gregory Y et al. 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
This blog was written by Dr Lisa Ang and was last updated in November 2020