Atrial Fibrillation Flashcards
What is the definition of AF?
a supraventricular tachyarrhythmia resulting from irregular, disorganised electrical activity and ineffective contraction of the atria
What is the ventricular rate in untreated AF?
the ventricular rate in untreated AF averages between 160-180 beats per minute
this is usually slower in older people
What does the P wave represent in a normal ECG?
atrial depolarisation
the atria are charged leading to contraction of the atrial muscles
there should be a p wave preceding each QRS complex
What does the QRS complex represent in a normal ECG?
depolarisation of the ventricles
What is represented by the T wave in a normal ECG?
ventricular repolarisation
there is a decrease in voltage, restoring a negative internal charge and relaxing the ventricular muscles
What is the R-R interval?
the distance between the peak of one R wave and the peak of the next R wave
represents the time between 2 QRS complexes
How does AF appear on an ECG?
absent P waves:
this is because the atria are not contracting properly
irregular RR intervals / QRS complexes:
resulting in an irregularly irregular ventricular rate
What are the 4 different categories of AF?
- initial episode
- paroxysmal
- persistent
- permanent
What is meant by an “initial episode”?
AF for 30 seconds or more diagnosed by an ECG
What is meant by paroxysmal AF?
- episodes lasting 30 seconds or more but for less than 7 days
- they are self-terminating (often within 48 hours) and recurrent
paroxysmal = sudden and recurring
What is meant by persistent AF?
- episodes lasting for more than 7 days
- or lasting less than 7 days but requiring pharmacological or electrical cardioversion
What is meant by permanent AF?
- longstanding AF (usually over 1 year) in which cardioversion has not been indicated / attempted
OR
- AF which fails to terminate using cardioversion or is terminated by relapses within 24 hours
when cardioversion is not attempted, this is called “accepted permanent AF”
What is the typical pattern that AF tends to follow?
- it starts as silent and unknown
- a first episode is documented
- the episodes become more frequent and obvious with time and begin to present with symptoms
How does AF typically tend to occur at first?
How does this change over time?
- initially it occurs in bouts, which are either self-terminating or stop after cardioversion
- it becomes gradually more frequent
- eventually, it becomes long-standing and permanent due to changes in the heart that mean it is no longer able to sustain sinus rhythm
In general, what treatments are present throughout the whole course of AF and which ones are added later on?
Anticoagulation:
this should start from the first episode and continue for as long as the stroke risk is high and bleeding risk is acceptable
Rate control:
starts from first episode and continues indefinitely
Antiarrhythmic drugs / catheter ablation:
used with varying success later on
Cardioversion:
these are intermittent and do not affect the disease process
How common is AF?
Who tends to be more affected?
- affects 2.5% population in England
- affects the elderly - 5-15% prevalence at 80 / < 0.5% at 40-50
- affects males more than females 1.5:1
What are the 2 most common causes of AF?
- hypertension
- ischaemic heart disease
What other heart conditions can result in AF?
- valvular heart disease
- congenital heart disease
- heart failure
What other conditions can cause AF?
- diabetes
- obesity
- hyperthyroidism
- sleep apnoea / chronic lung disease
- acute infection
- electrolyte depletion (hypokalaemia + hyponatraemia)
(remember as IN SHOCK)
Why does hypertension (and other conditions) cause AF?
- the heart has to work harder to pump blood around the body, resulting in LV hypertrophy
- this results in higher LA pressures
- this causes changes such as dilatation and fibrosis in the LA, resulting in AF
the same pathology applies to most of the causes of AF as they increase the strain on the heart
treating these conditions can result in improvement / resolution of AF
What is the most common presentation of AF in primary care?
it is most commonly an incidental finding
- on examination as an irregularly irregular pulse
- or on an ECG performed for another reason
If someone with AF is symptomatic, how might they present?
- shortness of breath
- palpitations
- chest discomfort
- syncope / dizziness
- reduced exercise tolerance / malaise
or they may present with the complications of AF - such as heart failure, stroke/TIA
What is the first-line investigation for suspected AF?
12-lead ECG
if this does not show AF, but there is high clinical suspicion then arrange a longer recording with 24 hour ambulatory ECG monitoring
As well as an ECG, what blood tests might be performed in initial investigations for AF?
- FBC, U&Es, TFTs
- HbA1c to screen for diabetes
- lipid profile with cardiovascular risk assessment
- BNP if there is suspicion of undiagnosed HF
- LFTs and clotting screen as anticoagulation is likely to be needed in the future
What other investigations may be considered if certain pathology was suspected?
CXR:
if underlying lung pathology was suspected
transthoracic echocardiogram:
if there is suspicion of underlying structural heart disease (e.g. murmur) or functional heart disease (e.g. HF)
When should a patient presenting with AF be immediately admitted to hospital?
if they have acute onset AF (within past 48 hours) with any sign of haemodynamic instability
or any signs of severe complications
they need resuscitation / stabilisation + considered for cardioversion
severe complications - stroke, HF, PE, thyrotoxicosis
What are the 3 primary objectives of long-term management in AF?
- stroke prevention
- symptom relief
- optimise management of concomitant cardiovascular disease
3 - includes HTN control, treatment of HF, management of diabetes / obesity, etc.
What are the mainstay ways of symptom relief?
- ventricular rate control
- rhythm control - with medicines, cardioversion + procedures
these DO NOT improve outcomes
there is no evidence that restoring sinus rhythm improves outcomes
so after anticoagulation - treatment aims at relieving symptoms
How can AF cause stroke?
- disorganised electrical activity within the atria causes ineffective contraction of the atrial muscle
- the blood is not sufficiently pumped out of the heart and can pool to form clots
- the clots can travel to the brain, block the vessels and cause a stroke
it is present in 15-20% acute strokes
AF increases stroke risk by 5% and is present in 15-20% acute strokes
Why are strokes as a result of AF particularly worrying?
What can be done to reduce this risk?
- associated with larger sized infarcts, increased disability, death, long-term care + recurrence
- result in impaired cognitive function + dementia
anticoagulation reduces stroke risk by 2/3
How is stroke risk assessed in AF?
Using the CHA2DS2VASc score
adding together the points allocated to each risk factor gives a total score, which guides decision to offer anti-thrombotic treatment
What parameters are accounted for in the CHADS-VASc score?
- C - congestive HF / LV dysfunction
- H - hypertension
- A - age >/= 75
- D - diabetes
- S - stroke / TIA
- V - vascular disease
- A - age 65-74
- Sc - sex category (female)
vascular disease includes previous MI, peripheral arterial disease, aortic plaques
According to the CHADS-VASc score, when should someone be offered anticoagulation?
- offer direct-acting oral anticoagulation (DOAC) when score is 2 or more
- consider anticoagulation in men with a score of 1 or more
anticoagulation is considered in a score of 1+ as long as the person has not just scored a point for being female
What is the first line anticoagulation treatment offered following CHADS-VASc score?
What else needs to be considered?
- apixaban
- dabigatran
- edoxaban
- rivaroxaban
^ all suitable DOACs - bleeding risk must be calculated first
if DOACs are not suitable, a Vitamin K antagonist such as warfarin can be offered
After someone is started on anticoagulation, how often do they need reassessing?
reassessment needed at least annually to check:
* suitability for anticoagulation
* compliance / tolerance of treatment
* uncontrolled symptoms
How is bleeding risk calculated prior to offering anticoagulation?
using the ORBIT scoring tool
this identifies people at high risk of bleeding to help guide decisions about anticoagulation
When might someone score 2 points in the ORBIT score?
anaemia - shown by reduced haemoglobin:
- men with Hb < 130g/L
- women with Hb < 120g/L
history of bleeding
e.g. GI bleed, intracranial bleed, haemorrhagic stroke
When does someone score 1 point on the ORBIT scoring tool?
- age >/= 75
- eGFR < 60 ml/min/1.73m2
- on current antiplatelet treatment
How is the ORBIT score used to risk stratify patients into 3 groups?
Low risk:
ORBIT score of 0-2
Medium risk:
ORBIT score of 3
High risk:
ORBIT score of 4-7
What are the 3 different treatments that can be used for rate control?
- beta-blocker
- rate-limiting calcium-channel blocker
- digoxin
What is the first-line medication given for rate control?
beta-blocker - usually atenolol 50mg
this is cardioselective, once daily and cost effective
After starting someone on atenolol 50mg, how are they monitored?
- they are started on a low dose
- pulse and BP is reviewed after 1 week
- this is then titrated to the highest tolerated dose
- pulse and BP should be reviewed 1 week after EVERY dose change
What are the contra-indications to beta-blockers?
- asthma
- COPD
- heart block
- uncontrolled HF
What are examples of rate-limiting calcium channel blockers?
- diltiazem
- verapamil
used as an alternative when beta-blockers not suitable
When might digoxin be used for rate control?
tends to be used in sedentary, elderly patients with other co-morbidities (such as HF)
After starting someone on rate control, what should be done if their symptoms have not improved after 1 week?
- titrate the medication to the highest tolerated dose
- if still symptomatic, consider combination therapy with beta-blocker + digoxin OR diltiazem
- if symptoms are not controlled by combination therapy, refer to cardiology within 4 weeks
If first-line rate control with a beta-blocker is not effective, what can be done?
- refer for specialist input
- cardiology can offer rhythm control options
What are the 3 categories of rhythm control agents?
- medications
- cardioversion
- catheter ablation
What medications may be offered for rhythm control?
Why can these only be prescribed by specialists?
- beta-blockers - sotalol
- anti-arrhythmics - flecainide / propafenone
- amiodarone
these medications have side effects:
- flecainide - can cause ventricular arrhythmias
- amiodarone - can cause thyroid problems
When may cardioversion be offered?
- for acute-onset AF
- for individuals with persistent symptoms despite other treatments
What is meant by catheter ablation?
- it uses heat or freezing to the area of the heart that is causing an abnormal heart rhythm
- this destroys areas of heart muscle that are triggering the arrhythmias
- the aim is to prevent the triggering of AF
- it is a long, high-risk procedure
What is the preferred beta-blocker that is prescribed in heart failure?
bisoprolol
if patient is old with many comorbidities - start on low dose (1.25mg)
if HF is uncontrolled - do not prescribe beta-blockers or rate-limiting CCBs without specialist advice
