Cardiology: Atrial Fibrillation Flashcards
What is AF?
A condition where the electrical activity in the atria of the heart becomes disorganised, leading to fibrillation (random muscle twitching) of the atria and an irregularly irregular pulse.
Features of AF?
1) Irregularly irregular ventricular contractions
2) Tachycardia
3) Heart failure due to impaired filling of the ventricles during diastole
4) Increased risk of stroke
What node produces organised electrical activity that coordinates the contraction of the atria?
Sinoatrial node
Pathophysiology in AF?
AF occurs when electrical activity is disorganised, causing the contraction of the atria to become uncoordinated, rapid and irregular.
This chaotic electrical activity overrides the regular, organised activity from the SA node.
It passes through to the ventricles, resulting in irregularly irregular ventricular contraction.
How does AF increase the risk of stroke?
1) Uncoordinated atrial activity means the blood can stagnate in the atria, forming a blood clot (thrombus)
2) A thrombus formed in the left atrium may travel to the brain and block a cerebral artery –> ischaemi stroke
What is increased risk of stroke in AF patients?
5x higher
What are the 5 most common causes of AF?
Mneumonic: SMITH
S - Sepsis
M - Mitral valve pathology (stenosis or regurgitation)
I - IHD
T - Thyrotoxicosis
H - HTN
What 2 lifestyle factors can cause AF?
1) Alcohol
2) Caffeine
Presentation of AF?
- Often asymptomatic (often incidental finding e.g. after stroke)
- Palpitations
- Shortness of breath
- Dizziness or syncope (loss of consciousness)
- Symptoms of associated conditions (e.g., stroke, sepsis or thyrotoxicosis)
What is the key exam finding in AF?
Irregularly irregular pulse
What are the 2 main differentials for an irregularly irregular pulse?
1) AF
2) Ventricular ectopics
When do ventricular atopics disappear?
Ventricular ectopics disappear when the heart rate gets above a certain threshold.
With an irregularly irregular pulse, what does a regular heart rate during exercise suggest a diagnosis of ?
Ventricular ectopics
What investigation is required in all patients with an irregularly irregular pulse?
ECG
3 key ECG findings in AF?
1) Absent P waves
2) Narrow QRS complex tachycardia
3) Irregularly irregular ventricular rhythm
An echo can be used to investigate further in AF in cases of what?
1) Valvular heart disease
2) Heart failure
3) Planned cardioversion
What is paroxysmal AF?
episodes of atrial fibrillation that reoccur and spontaneously resolve back to sinus rhythm
(can last between 30 seconds and 48 hours)
Patients with a normal ECG and suspected paroxysmal atrial fibrillation can have further investigations.
What are 2 further investigations?
1) 24-hour ambulatory ECG (Holter monitor)
2) Cardiac event recorder lasting 1-2 weeks
What is valvular AF?
AF with significant mitral stenosis or a mechanical heart valve.
The assumption is that the valvular pathology has led to atrial fibrillation
What are the 4 types of AF?
1) first detected episode
2) paroxysmal
3) persistent
4) permanent
If episodes of AF terminate spontaneously, what is this called?
Paroxysmal
If episodes of AF are not self-terminating (usually last >7 days) what term is used?
Persistent
What is permanent AF?
in permanent AF there is continuous atrial fibrillation which cannot be cardioverted or if attempts to do so are deemed inappropriate.
What are the 2 key aspects of AF management?
1) rate or rhythm control –> beta blocker e.g. bisoprolol
2) stroke prevention; anticoagulation –> DOAC
Aim of rate control in AF?
Rate control aims to get the heart rate below 100
NICE guidelines (2021) suggest all patients with AF should have rate control as first-line.
What are 4 exceptions to this?
1) A reversible cause for their AF
2) New onset atrial fibrillation (within the last 48 hours)
3) Heart failure caused by atrial fibrillation
4) Symptoms despite being effectively rate controlled
What are 3 pharmacological options for rate control in AF?
1) beta blocker
2) Calcium-channel blocker (e.g.,
diltiazem or verapamil) (not preferable in heart failure)
3) Digoxin (only in sedentary people with persistent atrial fibrillation, requires monitoring and has a risk of toxicity)
What is the 1st line option for rate control in AF?
Beta blocker e.g. bisoprolol, atenolol
Aim of rhythm control in AF?
return the patient to normal sinus rhythm.
Rhythm control may be offered to patients with AF.
What are the 4 indications for rhythm control?
1) A reversible cause for their AF
2) New onset atrial fibrillation (within the last 48 hours)
3) Heart failure caused by atrial fibrillation
4) Symptoms despite being effectively rate controlled
What are 2 options for rhythm control in AF?
1) cardioversion
2) long-term rhythm control using medications
What are the 2 types of cardioversion?
1) immediate
2) delayed
When is immediate cardioversion used in AF?
1) AF present for <48 hours
2) Causing life-threatening haemodynamic instability
What are the 2 options for immediate cardioversion in AF?
1) pharmacological cardioversion
2) electrical cardioversion
What are the 2 options for pharmacological cardioversion?
1) flecainide
2) amiodarone
What is the drug of choice for pharmacological cardioversion in patients with structural heart disease?
amiodarone
What is the aim of electrical cardioversion?
Electrical cardioversion aims to shock the heart back into sinus rhythm using a cardiac defibrillator (done under sedation or general anaesthesia)
When is delayed cardioversion used in AF?
Delayed cardioversion is used if the atrial fibrillation has been present for more than 48 hours and they are stable.
What is recommended for delayed cardiversion?
Electrical cardioversion
What can be considered before and after electrical cardioversion to prevent AF from recurring?
Amiodarone
How long should the patient should be anticoagulated for before delayed cardioversion?
at least 3 weeks
What is first line option for long-term rhythm control?
Beta blockers
What are 3 pharmacological options for long term rhythm control?
1) beta blockers
2) Dronedarone
3) Amiodarone
Management of paroxysmal AF?
Patients may be appropriate for a “pill-in-the-pocket” approach –> they take a pill to terminate their AF only when they feel the symptoms starting.
Anticoagulation based on CHA2DS2-VASc score
Criteria for ‘pill in the pocket’ approach?
To be suitable for a pill-in-the-pocket approach, they must have infrequent episodes without structural heart disease.
They also need to be able to identify the signs of atrial fibrillation and understand when to take the treatment.
What is the usual treatment for a pill-in-the-pocket approach?
Flecainide
Where drug treatment for rate or rhythm control is not adequate or tolerated, what is next option?
Ablation
What are the 2 options for ablation in AF?
1) Left atrial ablation
2) Atrioventricular node ablation and a permanent pacemaker
Aim of ablation?
Burn area of abnormal electrical activity –> leaves scar tissue that does not conduct electrical activity.
The aim is to remove the source of the arrhythmia and restore normal sinus rhythm.
What is required post atrioventricular node ablation and a permanent pacemaker?
1) Permanent pacemaker to control ventricular contraction
2) Anticoagulation
What are 2 options for anticoagulation in AF?
1) DOACs –> 1st line
2) Warfarin –> if DOACs contraindicated
Every patient with a head injury whilst taking anticoagulation should have what investigation?
CT head to assess for an intracranial bleed
Some of the DOACs have agents available to reverse the effects in uncontrolled or life-threatening bleeding.
What is reversing agent for apixaban and rivaroxaban?
Andexanet alfa
What is reversing agent for idarucizumab?
a monoclonal antibody against dabigatran
Advantages of DOACs over warfarin?
1) No monitoring is required
2) No issues with time in therapeutic range (provided they have good adherence)
3) No major interaction problems
4) Equal or slightly better than warfarin at preventing strokes in atrial fibrillation
5) Equal or slightly lower risk of bleeding than warfarin
What are the 3 most common indications for DOACs?
1) stroke prevention in patients with AF
2) Treatment of DVT and PE
3) Prophylaxis of VTE after hip or knee replacement
Mechanism of warfarin?
Vitamin K antagonist –> prolongs prothrombin time
What is used to assess how anticoagulated the patient is by warfarin?
INR
What does the INR calculate?
The INR calculates the patient’s prothrombin time compared with the prothrombin time of an average healthy adult.
What does an INR of 2 mean?
An INR of 2 means the patient has a prothrombin time twice that of an average healthy adult (it takes them twice as long to form a blood clot).
Target INR for AF?
2-3
What is the time in therapeutic range (TTR)?
Refers to the percentage of time that the INR is in the target range.
Is warfarin metabolised by the P450?
yes
What foods can affect warfarin levels?
- leafy green vegetables (contain vitamin K)
- cranberry juice & alcohol (affect P450)
What can reverse the effects of warfarin?
Vitamin K can reverse the effects of warfarin in the event of a very high INR or significant bleeding.
What tool is used for assessing whether a patient with atrial fibrillation (even if its first episode) should start anticoagulation?
CHA2DS2-VASc
What does a higher CHA2DS2-VASc indicate?
The higher the score, the higher the risk of developing a stroke or TIA.
Describe the CHA2DS2-VASc
Each factor scores a point:
C – Congestive heart failure
H – Hypertension
A2 – Age above 75 (scores 2)
D – Diabetes
S2 – Stroke or TIA previously (scores 2)
V – Vascular disease
A – Age 65 – 74
S – Sex (female)
CHA2DS2-VASc score results:
0 – no anticoagulation
1 – consider anticoagulation in men (women automatically score 1)
2 or more – offer anticoagulation
What score is used or assessing the risk of major bleeding in patients with atrial fibrillation taking anticoagulation?
ORBIT score
O – Older age (age 75 or above)
R – Renal impairment (GFR less than 60)
B – Bleeding previously (history of gastrointestinal or intracranial bleeding)
I – Iron (low haemoglobin or haematocrit)
T – Taking antiplatelet medication
What is an option for patients with contraindications to anticoagulation and a high stroke risk in AF?
Left atrial appendage occlusion
