Atrial Fibrillation Flashcards
What is atrial fibrillation?
- most common sustained cardiac arrhythmia
- very common:
- 5% of patients over aged 70-75 years
- 10% of patients aged 80-85 years
- uncontrolled atrial fibrillation = symptomatic palpitations and inefficient cardiac function
- most important = reducing the increased risk of stroke
What are the classifications of AF?
- First detected episode (irrespective of whether it is symptomatic or self-terminating)
- Recurrent paroxysmal AF:
- If episodes of AF terminate spontaneously
- episodes last less than 7 days (typically < 24 hours)
- Recurrent persistent AF:
- If the arrhythmia is not self-terminating then the term persistent AF is used
- Such episodes usually last greater than 7 day
-
Permanent AF:
* there is continuous atrial fibrillation which cannot be cardioverted
OR if attempts to do so are deemed inappropriate
Treatment goals are therefore rate control and anticoagulation if appropriate
*NB: Recurrent means 2 or more episodes of AF
What are the symptoms and signs of AF?
Symptoms
- palpitations
- dyspnoea
- chest pain
Signs
- an irregularly irregular pulse
What are the most important parts of managing AF?
- Rate/rhythm control
- Reducing stroke risk
How do you control rhythm?
- Try to get the patient back into, and maintain, normal sinus rhythm. This is termed cardioversion:
- Drugs (pharmacological cardioversion)
- Synchronised DC electrical shocks (electrical cardioversion)
For many years the predominant approach was to try and maintain a patient in sinus rhythm. This approach changed in the early 2000’s and now the majority of patients are managed with a rate control strategy. NICE advocate using a rate control strategy except in a number of specific situations such as coexistent heart failure, first onset AF or where there is an obvious reversible cause.
What is the rate control strategy?
A beta-blocker or a rate-limiting calcium channel blocker (e.g. diltiazem) is used first-line to control the rate in AF
If one drug does not control the rate adequately NICE recommend combination therapy with any 2 of the following:
- a betablocker
- diltiazem
- digoxin
What is the rhythm control strategy?
- There are a subgroup of patients for whom a rhythm control strategy should be tried first.
- Other patients may have had a rate control strategy initially but switch to rhythm control if symptoms/heart rate fails to settle.
- When considering cardioversion it is very important to remember that the moment a patient switches from AF to sinus rhythm presents the highest risk for embolism leading to stroke.
- Imagine the thrombus formed in the fibrillating atrium suddenly being pushed out when sinus rhythm is restored.
- For this reason patients must either have had a short duration of symptoms (less than 48 hours) or be anticoagulated for a period of time prior to attempting cardioversion.
How do you determine stroke risk?
CHA2DS2-VASc score to determine the most appropriate anticoagulation strategy
What anti-coagulation therapy does NICE recommend?
- NICE recommend that we offer patients a choice of anticoagulation, including warfarin and the novel oral anticoagulants (NOACs)
- Aspirin is no longer recommended for reducing stroke risk in patients with AF
How is bleeding risk from warfarin stratified?
Using the HASBLED score
NO formal rules on HASBLED score
Score of >= 3 indicates a ‘high risk’ of bleeding, defined as intracranial haemorrhage, hospitalisation, haemoglobin decrease >2 g/L, and/or transfusion
When is cardioversion used in AF?
- electrical cardioversion as an emergency if the patient is haemodynamically unstable
- electrical or pharmacological cardioversion as an elective procedure where a rhythm control strategy is preferred
What should happen if AF onset is < 48 hours?
- Patients should be heparinised.
- Patients who have risk factors for ischaemic stroke should be put on lifelong oral anticoagulation
- Otherwise, patients may be cardioverted using either:
- electrical - ‘DC cardioversion’
- pharmacology - amiodarone if structural heart disease, flecainide or amiodarone in those without structural heart disease
- Following electrical cardioversion if AF is confirmed as being less than 48 hours duration then further anticoagulation is unnecessary
What should happen if AF onset is > 48 hours?
- Anticoagulation should be given for at least 3 weeks prior to cardioversion
- An alternative strategy:
- perform a transoesophageal echo (TOE) to exclude a left atrial appendage (LAA) thrombus
- If excluded patients may be heparinised and cardioverted immediately
- NICE recommend electrical cardioversion in this scenario, rather than pharmacological.
- If there is a high risk of cardioversion failure (e.g. Previous failure or AF recurrence) then it is recommend to have at least 4 weeks amiodarone or sotalol prior to electrical cardioversion
- Following electrical cardioversion patients should be anticoagulated for at least 4 weeks. After this time decisions about anticoagulation should be taken on an individual basis depending on the risk of recurrence
What agents should be used in pharmacological cardioversion?
Agents with proven efficacy in the pharmacological cardioversion of atrial fibrillation
- amiodarone
- flecainide (if no structural heart disease)
- others (less commonly used in UK): quinidine, dofetilide, ibutilide, propafenone
Less effective agents
- beta-blockers (including sotalol)
- calcium channel blockers
- digoxin
- disopyramide
- procainamide
What are the guidelines for AF post-stroke?
Management of patients with AF who develop a stroke or transient-ischaemic attack (TIA).
- following a stroke or TIA:
- warfarin or a direct thrombin or factor Xa inhibitor given as the anticoagulant of choice.
- Antiplatelets should only be given if needed for the treatment of other comorbidities
- in acute stroke patients, in the absence of haemorrhage, anticoagulation therapy should be commenced after 2 weeks
- If imaging shows a very large cerebral infarction then the initiation of anticoagulation should be delayed
How do you control rate and maintain sinus rhythm in AF?
Agents used to control rate in patients with atrial fibrillation
- beta-blockers
- calcium channel blockers
- digoxin (not considered first-line anymore as they are less effective at controlling the heart rate during exercise. However, they are the preferred choice if the patient has coexistent heart failure)
Agents used to maintain sinus rhythm in patients with a history of atrial fibrillation
- sotalol
- amiodarone
- flecainide
- others (less commonly used in UK): disopyramide, dofetilide, procainamide, propafenone, quinidine
