Atrial fibrillation Flashcards
What is AF?
condition involving irregular contraction of the ventricles due to fibrillation of the atria. If not properly managed this condition can result in significant complications including cardioembolic stroke.
What is atrial contraction like?
Ineffective
What is ventricular contraction like?
Irregular
What is the epidemiology for AF?
AF is the most common cardiac arrhythmia in adults. The prevalence of AF increases with age, particularly over 65 years, such that 10% of over 85-year-olds have atrial fibrillation
What are the 3 types of AF?
- Paroxysmal
- Persistent
- Permanent
What is paroxysmal AF?
Episodes may last longer than 30 seconds but less than 7 days and are self-terminating but recurrent
What is persistent AF?
episodes last less than or more than seven days but require electrical or chemical cardioversion
What is permanent AF?
episodes fail to terminate with cardioversion OR a terminated episode that relapses within 24 hours OR long-standing AF (usually >1 year) in which cardioversion has not been indicated or attempted
What is the aetiology of the cardiac conducting system?
- Cardiac impulses are first generated in the sinoatrial node which is found in the right atrium.
- The rate at which these impulses are generated is under the influence of the autonomic nervous system
- The sympathetic branch of the nervous system increases the rate of impulse generation from the SAN whereas the parasympathetic branch decreases the rate of impulse generation
4.The electrical impulses travel through the atria causing atrial contraction and to the atrioventricular node which lies between the aria and ventricles. - The AVN briefly delays the impulse which then travels through the bundle of His, down the left and the right bundle branches and finally to the purkinje fibres resulting in ventricular contraction
What type of arrhythmia is AF?
supraventricular cardiac arrhythmia
What does the AF arrhythmia typically originate from?
Left atrial myocytes
What do atrial ectopics from the pulmonary veins typically trigger?
Micro re-entry circuits in the atria causing chaotic electrical activity and sustained AF
What conditions exacerbate AF?
- Mitral regurgitation
- hypertension
Conditions including hypertension or mitral regurgitation cause the atria to stretch which changes their electrical properties increasing the substrate for AF. The combination of trigger and substrate leads to an increased likelihood that an atrial ectopic triggers AF and the atria sustain it.
What is the ventricular rate like in AF?
In AF, the ventricular rate is very variable and depends on the speed of AVN conduction. Young patients with slick AV nodes are often very symptomatic and tachycardic.
What is the result of ineffective atrial contraction?
The consequence of this is blood stasis within the atria which increases the chance of thrombosis (Virchow’s triad) and subsequently embolic complications including transient ischaemic attacks (TIA), stroke and systemic embolisation
True or false: only a proportion of the uncoordinated wavelets are conducted to the ventricles in atrial fibrillation
True
Give the 5 key aetiological causes of atrial fibrillation: (SMITH)
1) sepsis
2) mitral valve pathological
3) ischaemic heart disease
4) thyrotoxicosis
5) hypertension
Describe how sepsis can cause atrial fibrillation:
the presence of stress hormones and hypotension results in an increased intracardiac pressure resulting in dilation of the atria, disturbing electrical signalling
Describe how mitral valve pathology can cause atrial fibrillation:
stenosis or regurgitation of the mitral valve creates a backlog that increases intra-atrial pressure, dilating the atria and disrupting electrical signalling
Describe how ischaemic heart disease can cause atrial fibrillation:
cell death results in disruption to electrical signalling
Describe how thyrotoxicosis can cause atrial fibrillation:
thyroid hormones are associated with the shortening of action potential duration (hence TFTs are mandatory for any patient with AF)
Describe how hypertension can cause atrial fibrillation:
increased systemic pressure causes a backlog, increasing intra-atrial pressure causing structural dilation of the atria and so disruption to electrical signalling
Give 8 general risk factors for atrial fibrillation:
1) age
2) obesity
3) smoking
4) diabetes
5) hypertension
6) caffeine
7) metabolic syndrome
8) alcohol
Give 4 key presenting features of atrial fibrillation:
1) irregularly irregular pulse (maintained in exercise)
2) palpitations and tachycardia
3) chest pain
4) shortness of breath
Describe heart sounds in atrial fibrillation:
the first heart sound has variable intesity and loudness
How does AF present on an ECG? (3)
1) rapid and irregular QRS complexes
2) absent P waves
3) presence of F waves (fine oscitations of the baseline)
Other than ECG, name 5 other investigations used in the management of AF:
1) echocardiogram
2) FBC (check for infection and anaemia)
3) TFTs (thyroid hormones can shorten action potential duration)
4) U&Es (electrolyte disturbances)
5) cardiac markets (CK-MB, troponin - for signs of ischaemic heart disease)
Name 9 cardiac causes of AF?
- Heart failure
- Structural pathology
- Congenital heart disease
- Atrial or ventricular dilation
- Atrial or ventricular hypertrophy
- Pre-excitation syndromes
- Sick sinus syndrome
- Inflammatory conditions
- Infiltrative conditions
What are the risk factors for AF?
Male sex
Caucasian ethnicity
Increasing age
Alcohol
Cigarette smoking
Obesity
Co-morbidities (e.g. chronic kidney disease and obstructive sleep apnoea)
Caffeine intake is not typically a risk factor although it is often blamed for palpitations.
What are 6 typical symptoms of AF?
- Breathlessness
- Chest discomfort
- Palpitations
- Light-headedness
- Reduced exercise intolerance
- Syncope
TIA can be the presenting feature of AF.
What are the typical clinical finding upon examination in a patient with AF?
Irregularly irregular pulse when palpating either the radial or carotid arteries or auscultating at the apex.
Radial-apical deficit: this is important to assess because each ventricular contraction may not be sufficiently strong enough to transmit a pulse to the radial artery and palpating only the radial artery can miss tachycardia.
What is atrial flutter?
organised atrial rhythm with a very fast rate of 250-350bpm with typically every second flutter beat conducting
How does atrial flutter present on an ECG?
sawtooth-like F waves between QRS complexes
What is Wolff-Parkinson-White syndrome?
a ventricular preexcitation syndrome where an accessory conduction pathway from atria to ventricle bypassing AV node, causing ventricles partially depolarise early
What are ventricular ectopics?
Premature ventricular beats caused by random electrical discharges from outside the atria
Ventricular ectopics disappear when heart rate reaches a certain threshold
What is cardioversion?
the delivery of synchronised electrical shocks to the myocardium or IV administration of an antiarrhythmic drug
What does the European society of cardiology state must be met for a diagnosis of AF?
A standard 12-lead ECG recording or a single-lead ECG recording of ≥30 seconds showing a heart rhythm of no discernible repeating P-waves AND
Irregular RR intervals
What would the ECG finding be for a patient with AF?
- Ventricular rate 100-180bpm
- Irregular rhythm
- No P waves, with oscillating baseline waves
Give the 4 steps in acute management of AF:
1) give oxygen
2) give anticoagulants
3) give rate controlling beta blocker (bisoprolol) or calcium channel blocker (verapamil) - use digoxin as a second line
4) consider cardioversion
Give an example of an antiarrhythmic drug that can be used in cardioversion:
flecanide
Describe the ‘pill in the pocket’ approach used for patients with paroxysmal AF:
patient is given an antiarrhythmic such as flecainide to take when they feel symptoms of AF starting
What are the two long term management strategies for AF:
1) rate control (by slowing the AV node)
2) rhythm control (cardioversion)
+both with anticoagulation
Name 3 drugs that can be used to control heart rate by slowing the AV node:
- Beta blockers
- Calcium channel blockers
- digoxin
How does slowing heart rate help manage AF?
it allows the ventricles more time to fill (in AF, uncoordinated contractions do not allow a long enough diastole period)
Why are patients with AF given anticoagulation drugs?
to prevent a secondary thromboembolic event such as a stroke
What does INR stand for?
international normalised ratio
What is INR?
A method of assessing a patient’s level of anticoagulation by comparing prothrombin time of a patient with the prothrombin time of a normal health adult
Name the scoring system used to assess the need for anticoagulation drugs in AF:
CHA2DS2-VASc
Give the 8 points of the CHA2DSVASC anticoagulation scoring system:
1) congestive heart failure
2) hypertension
3) age 75+ (2 points)
4) diabetes
5) stroke/ TIA/ thromboembolism (2 points)
6) vascular disease
7) age 65-74 (1 point)
8) sex category
What CHA2DS-VASc score would indicate need for anticoagulants in AF
2
What is the name of the online calculator that assesses a patient’s risk of bleeding whilst on anticoagulation?
ORBIT
Give some examples of factors considered by the ORBIT bleed risk calculator: (5)
1) low haemoglobin
2) age 75+
3) previous major bleeds
4) GFR >60
5) antiplatelet medication
Describe how treatment varies in patients who have been in AF for >48 hours:
anticoagulation should be given at least 3 weeks prior to cardioversion (patients who have been in AF for <48 hours should be heparinised and cardioverted)
What group of anticoagulants are considered first line in the long term management of AF?
DOACs (direct oral anticoagulants)
What anticoagulant is considered first line in the acute admission management of AF?
LMWH (low molecular weight heparin)
What class is Flecainide?
class 1c antiarrhythmic drug that blocks sodium channels within the heart and thereby raises the threshold for depolarisation. It should not be used in patients with evidence of structural or ischaemic heart disease because of the risk of sudden cardiac death. Flecainide can be given orally or intravenously.
What class is amiodarone?
class 3 antiarrhythmic drug that blocks potassium channels within the heart and thereby prolongs the refractory period of the myocardium. It can be used in patients with evidence of structural heart disease. Amiodarone may prolong the QT interval and should be avoided in patients with QT prolongation.
What is the HAs-BLED score?
The HAS-BLED score is used to assess risk of bleeding in these patients, to guide in weighing up the risk of anticoagulation.
What is the SOFA score?
The SOFA score is an organ failure assessment tool
What is the alvarado score?
used to estimate the likelihood of acute appendicitis.
What are 3 complications of AF?
- Thromboembolic stroke
- Heart failure
- Syncope
