Atrial Fibrillation Flashcards
What is atrial fibrillation?
When the atrial muscle fibres contract independently of ventricular muscle fibres. The AV node is bombarded with depolarisation waves of varying strength from the independently fibrillating cardiac muscles.
Depolarisation spreads down the bundle of His at irregular intervals in an all or nothing fashion. This means that the depolarisation is of constant intensity. However, the ventricles contract irregularly (rhythm wise).
What are the characteristics of atrial fibrillation on an ECG?
- No P waves, and an irregular baseline
- Irregular QRS complex, which are normally shaped
- Waves can be seen in V1 which resemble atrial flutter
How much does cardiac output drop by in atrial fibrillation?
10-20%
What is the main risk from atrial fibrillation?
Embolic stroke
Why is atrial fibrillation associated with left or right atrial enlargement?
An enlarged atrium increases the potential for re-entrant circuits
What are causes of AF?
- MI
- Heart failure/Ischaemia
- Hypertension
- Hyperthyroidism
- PE
- Pneumonia
- Caffeine
- Alcohol
- Decreased K+, Mg2+
- Cardiomyopathy
- Constrictive pericarditis
- Sick Sinus syndrome
- Lung Cancer
- Endocarditis
- Atrial myxoma
- Haemochromatosis
Why is atrial fibrillation potentially dangerous?
Compromisation of cardiac output -> Hypertension and pulmonary congestion
Blood stasis in the atria -> thrombus formation (particularly left atrial appendage)
What are the main aspect of approaching the management of AF?
- Ventricular rate control
- Restore sinus rhythm
- Assessemtn for need to anticoagulate
What are the symptoms of someone with AF?
Can be asymptomatic
If symptomatic
- Chest pain
- Palpitations
- Dyspnoea
- Syncope
- Fatigue/Faintness
What are signs of AF?
- Irregularly Irregular rhythm
- Apical pulse rate > radial pulse rate
- S1 of variable intensity
- Signs of LVF
If someone presented with Chest pain, palpitations and syncope, what investigations would you do?
- Vital signs
- ECG
- Bloods - U+E’s, Troponin, TFTs
- ECHO
What are the different classifications of AF?
- First detected
- Paroxysmal
- Persistent
- Permanent
How would you manage someone with Acute AF who was very unwell or showing signs of haemodynamic instability?
- ABCDE
- Give Oxygen
- IV access
- Take U+E’s and any other bloods
- Emergency cardioversion - if unavailable - IV amiodarone 300 mg over 1hr
What is haemodynamic instability?
Means that he/she has a stable heart pump and good circulation of blood. Hemodynamic instability is defined as any instability in blood pressure which can lead to inadequate arterial blood flow to organs.
Signs can include heart failure, Shock, syncope
If someone was haemodynamically stable with symptomatic AF, how would you manage them?
- Give oxygen if needed
- Assess for heart failure
- Determine thromboembolism and bleeding risks
- Perform ECHO - look for TE
- Treat based on “48 hr window” and presence of TE
How would you assess someone with AF for thrombus?
Transoesophageal ECHO
How would you manage someone with chronic AF?
- Rate control
- Rhythm control
- Anticoagulation
When treating chronic AF, what would you do to try and control rate?
- 1st line - B-blockers (bisoprolol) or CCB (verapimil, diltiazem)
- 2nd line - add digoxin, then amiodarone if digoxin fails
When would you use digoxin or amiodarone to treat acute AF as a first line?
If the patient has heart failure
When treating chronic AF, what would you do to try and control rhythm?
- DC/Pharmacological cardioversion
- Ablate and pace - ablate AV node, insert pacemaker
- Pulmonary vein ostial ablation
- Maze procedure
How would you anticoagulate someone with Chronic AF?
- Warfarin/DOACs
- Can use aspirin instead
What are indications for cardioversion in someone with acute AF?
- < 48 hrs - Very unwell/haemodynamically unstable + presentation within 48 hour window
- >48 hours - anticoagulation for 3 weeks prior to cardioversion, and continue for 4 weeks after cardioversion (longer if high risk for stroke)
- Thrombus ruled out by TOE
Why is the apical pulse sometimes greater than the radial pulse?
In atrial fibrillation, the ventricles don’t fill properly, but still contract. Therefore, the contraction of the ventricles is felt at the apex, but the cardiac ouput becomes reduced, meaning that each contraction doesn’t always cause a palpable radial pulse.
Often the radial pulse can be up to 20 bpm less than the apical pulse
What are the two main possible explanations for an irregularly irregular pulse?
- AF
- Ventricular ectopics
How would you distinguish clinically between AF and ventricular ectopics as a cause for an irregularly irregular pulse?
Exercise the patient - if the irregular pulse dissapears, then ventricular ectopics; if it remains, then AF is the cause.
What symptoms might prompt you to check for an irregularly irregular pulse/AF?
- Dyspnoea
- Palpitations
- Syncope
- Dizzy spells
- Chest discomfort
- Stroke/TIA
How is paroxysmal AF defined?
Atrial fibrillation that terminates spontaneously within 7 days - but usually within 48 hours
What scoring system could you use to determine the thromboembolism risk of someone with AF?
CHA2DS2-VASc
What scoring system could you use to determine bleeding risk in AF who has been started on anticoagulation?
HAS-BLED scoring system
When would you consider digoxin as a monotherapy?
People with non-paroxysmal atrial fibrillation only if they are sedentary (do no or very little physical exercise).
What is the first line choice for chemical cardioversion in chronic AF?
Flecanide - Only if no structural abnormality
Why would you not give B-blocker and verapamil/diltiazem in someone with chronic AF?
Bradycardia risk - only give with expert advice
How would you treat chronic paroxysmal AF?
Either rhythm control, or PILL IN POCKET
- B-blocker/Flecanide PRN
What would you have to check before putting someone on a “pill in pocket regimen” for chronic paroxysmal AF?
- No past LV dysfunction
- Episodes are infrequent
- BP >100 and pulse is normal
If someone had structural heart disease, what treatment would you give to chemically cardiovert them if they had chronic AF?
IV amiodarone
If someone had acute AF for <48 hrs and was haemodynamically stable, how would you manage them?
- Assess TE tisk - ECHO
- If No TE - DC/Pharmocological cardioversion
If someone had acute AF for >48 hrs and was haemodynamically stable, how would you manage them?
- Assess for TE - ECHO
- If no TE - Establish LMWH, then DC cardioversion
If someone had acute AF, was haemodynamically stable, and was found to have thromboembolism on ECHO, how would you manage them?
LMWH + Warfarin/DOAC, then cardioversion after 3-4 weeks
If someone had haemodynamically stable AF, and didn’t have heart failure, what medications could you use for rate control?
- B-blockers
- CCB
If someone had acute AF and was in HF, what medications could you use for rate control?
- Digoxin
- Amiodarone
In a patient with AF taking warfarin, what level of INR would you aim for?
2-3
In a patient with AF taking warfarin who had a mechanical valve, what INR would you aim for?
3-4 -> 3.5 best
What are the 3 most common causes of AF?
- Ischaemic heart disease
- Rheumatic Heart disease
- Mitral Stenosis
If you were going to DC cardiovert someone with chronic AF in an adept to control rhythm, what would you want to do before performing the cardioversion?
- ECHO
-
Pre-treat for >/= 4 weeks with amiodarone or sotalol if risk of failure
- Past failure
- Past recurrence
