Atrial Fibrillation Flashcards
What is atrial fibrillation (AF)?
It is where the contraction of the atria is uncoordinated, rapid and irregular
What is the most common arrhythmia?
AF
Describe the pathophysiology of AF
It is due to disorganised electrical activity that overrides the normal, organised activity from the sinoatrial node
This disorganised electrical activity in the atria also leads to irregular conduction of electrical impulses to the ventricles
What are the three classifications of AF?
Paroxysmal
Persistent
Permanent
What is paroxysmal AF?
It is when the AF comes and goes in episodes, usually not lasting more than 48 hours
They do not last longer than 7 days
What is persistent AF?
It is when the AF comes and goes in episodes that do not self terminate
These episodes usually last greater than 7 days
What is permanent AF?
This is when there is continuous AF which cannot be cardioverted or if attempts to do so are deemed inappropriate
What are the five causes of AF?
mrs SMITH
Sepsis
Mitral valve pathology
Ischaemic heart disease
Thyrotoxicosis
Hypertension
How does AF usually present?
Asymptomatically
What are the six clinical features of AF?
Irregularly, Irregular Pulse
Increased Heart Rate, 300 – 600bpm
Palpitations
Dyspnoea
Syncope
Chest Pain
What other condition also results in the presentation of an irregular, irregular pulse?
Ventricular ectopics
How do we differentiate between AF and ventricular ectopics?
Ventricular ectopics disappear when the heart rate gets over a certain threshold
Therefore, a regular heart rate during exercise suggests a diagnosis of ventricular ectopics
What investigation is used to diagnose AF?
ECG scan
What are the three signs of AF on ECG?
Absent P waves
Narrow QRS complex tachycardia
Irregularly irregular ventricular rhythm
What are the two aims when managing AF?
Rate/rhythm control
Reducing stroke risk
What do we usually chose to control in AF - rate or rhythm?
It is first line to control rate rather than rhythm
In what three circumstances do we chose to control rhythm over rate in AF?
There is a reversible cause for their AF
The AF is of new onset (within 48 hours)
The AF is causing heart failure
What do we aim to reduce the heart rate to in AF? Why is this important?
< 100bpm
It extends the time during diastole when the ventricles can fill with blood, increasing CO
What are the three management options used to control rate in AF?
Beta-blocker
Calcium channel blocker
Digoxin
What is the first line management option used to control rate in AF? Name an example
Beta-blocker
Atenolol 50-100mg once daily
What is a common contraindication for beta-blockers?
Asthma
What CCB is used to control the rate of AF? When is it contraindicated?
Diltiazem
Heart failure
When is digoxin administered to control rate in AF?
In sedentary patients - who do no/very little physical exercise
What is the mechanism of action of digoxin?
It inhibits the Na/K ATPase pump
How do we aim to control rhythm in AF? What is this called?
We aim to return the patient to normal sinus rhythm
Cardioversion
What are the two types of cardioversion?
Immediate
Delayed
When is immediate cardioversion conducted?
In cases where the AF has been present for less than 48 hours or they are severely haemodynamically unstable
When is delayed cardioversion conducted?
In cases where the AF has been present for more than 48 hours and they are stable
Prior to delayed cardioversion, what do we administer to patients? Why?
Anticoagulants for 3 weeks
48 hours prior to cardioversion patients may have developed a blood clot in the atria and reverting them back to sinus rhythm carries a high risk of mobilising that clot and causing a stroke
What are the two options for cardioversion?
Pharmacological
Electrical
What two drugs are used in pharmacological cardioversion?
Flecainide
Amiodarone
When is amiodarone selected in pharmacological cardioversion?
Structural heart disease
What is electrical cardioversion?
It involves rapidly shocking the heart back into sinus rhythm using a cardiac defibrillator machine
These patients are sedated or given general anaesthetic prior to the procedure
What is electrical cardioversion synchronised to? Why?
R wave
This is to prevent delivery of a shock during the vulnerable period of cardiac repolarisation when ventricular fibrillation can be induced
When is electrical cardioversion preferred over pharmacological cardioversion?
In haemodynamically unstable patients, with decompensation
What drug should patients be administered following electrical cardioversion? For how long?
Anticoagulants
Lifelong
What three drugs are used to manage rhythm of AF long term?
Beta blockers
Dronedarone
Amiodarone
What is the first line long term rhythm control drug?
Beta blockers
What is the second line long term rhythm control drug?
Dronedarone
When is amiodarone used to control rhythm long term?
In patients with heart failure or left ventricular dysfunction
What drug class is used to reduce the risk of stroke in AF patients?
Anticoagulants
How can AF result in the development of a stroke?
The uncontrolled and unorganised movement of the atrium leads to blood stagnating in the left atrium, particularly in the atrial appendage
This stagnated blood leads to a thrombus
This clot then embolisms and travels within the blood
It travels from the atria, to the ventricle, to the aorta then up in the carotid arteries to the brain
It can then lodge in the cerebral arteries and cause an ischaemic stroke
What type of stroke does AF cause?
Ischaemic
What scoring system is used to assess whether a patient should be put on anticoagulants?
CHAS2DS2-VASc
What is the CHA2DS2-VASc score?
Congestive heart failure (1 point)
Hypertension (1 point)
Age > 75 (2 points)
Age 65-74 (1 point)
Diabetes (1 point)
Prior Stroke/TIA/VTE (2 points)
Vascular disease (1 point)
Sex Female (1 point)
What management option is suggested in patients with a CHA2DS2-VASc score of 0?
No treatment
What management option is suggested in patients with a CHA2DS2-VASc score of 1?
Males - CONSIDER anticoagulation
Females - no treatment (this is because their score of 1 is only reached due to their gender)
What management option is suggested in patients with a CHA2DS2-VASc score of 2?
OFFER anticoagulation
What is the first line anticoagulant used in AF?
Direct oral anticoagulants (DOACs)
What are the four DOACs used in AF?
Apixaban
Dabigatran
Edoxaban
Rivaroxaban
Which DOAC is preferred in individuals with renal impairment?
Apixaban
What is the second line anticoagulant used in AF?
Warfarin
What is the mechanism of action of Warfarin?
It is a vitamin K antagonist
This prolongs the prothrombin time, which is the time it takes for blood to clot
What is the function of vitamin K?
It is essential for the functioning of several clotting factors
Why is it important that we monitor Warfarin regularly?
It is affected by the cytochrome P450 system in the liver. Therefore INR will be affected by drugs that influence the activity of the P45O system
It is affected by foods, particularly those containing vitamin K (leafy green vegetables) and those that affect P450 (cranberry juice, alcohol)
How do we monitor Warfarin?
INR (international normalised ratio)
What is the INR?
It is a calculation of how the prothrombin time of the patient compares with the prothrombin time of a normal healthy adult
What INR reading indicates a normal prothrombin time?
1
What is the target INR reading for AF?
2-3
How do we reverse the effects of Warfarin when the INR is too high or bleeding has occurred?
Vitamin K
What anticoagulant is contraindicated in AF?
Aspirin
What scoring system is used to establish a patient’s risk of major bleeding whilst on anticoagulants/prior to administration?
HAS-BLED
ORBIT
What is the HAS-BLED score?
It is a score based on…
Hypertension
Abnormal renal and liver function
Stroke
Bleeding
Labile INRs
Elderly
Drugs/alcohol
What do NICE guidelines recommend in terms of assessing bleeding risk?
They state that a history of falls, old age and alcohol excess should not result in anticoagulation withholding
How do we manage paroxysmal AF?
A ‘pill in the pocket’ approach with flecanide
This is where they take a pill to termite their AF when they feel the symptoms of AF staring
When is flecanide contraindicated? Why?
Atrial flutter
It causes 1:1 AV conduction and results in a significant tachycardia
Do we start individuals with paroxysmal AF on anticoagulation?
Yes - we calculate their CHA2DS2-VASc score and consider a DOAC
This is relevant is only a single episode
