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Gold standard case presentation
Atrial fibrillation (AF) is the most common arrhythmia with a prevalence of up to 2% of the population. It is more common in men than women. AF causes an irregularly irregular heart beat that results from disorganised atrial electrical activity and irregular atrioventricular conduction. This results in a reduction of up to 50% of cardiac output as well as an inconsistent stroke volume.
- no distinct p-waves;
- irregular R-R intervals;
- variable atrial cycle duration;
- may be asymptomatic;
- shortness of breath (at rest or on exertion);
- reduced exercise tolerance;
- syncope or pre-syncope;
- symptoms from associated disease (such as heart failure).
Classification of symptoms:
- European Heart Rhythm Association score I – asymptomatic
- European Heart Rhythm Association score II – mild symptoms with no effect
- pon ADLs (activities of daily living);
- European Heart Rhythm Association score III – severe symptoms with ADLs affected;
- European Heart Rhythm Association score IV – disabling symptoms with ADLs unable to be carried out at all.
AF can be persistent or paroxysmal (intermittent), and both confer the same risk of stroke (see below). AF can be classified based upon the duration of symptoms:
- First diagnosed AF – Initial presentation of first episode;
- Paroxysmal – Self terminates and usually present for < 48 hours, but can be present for < 7 days;
- Persistent – AF lasting for > 7 days;
- Long standing AF – AF that has lasted > 1 year;
- Permanent – AF persisting > 7 days where decision has been made not to pursue rhythm control
Causes of AF:
- coronary artery disease;
- heart failure (including cardiomyopathies);
- congenital heart defects (ASD or VSD for example);
- valvular heart disease, particularly mitral valve disease;
- thyroid dysfunction;
- alcohol excess;
- caffeine excess.
- Stroke. Stasis of the blood in the primarily left atrial appendage leads to the development of thrombi, which leads to cerebrovascular accidents. In patients aged between 80-89, there is a risk of nearly 25% for stroke with AF. Compared to the general population, there is a five times increased risk of stroke with AF. This risk can be assessed using the CHA2DS2VASC score (see below)
- heart failure
- full blood count (infection and anaemia);
- biochemsitry (electrolyte disturbance);
- thyroid function tests (hyperthyroidism).
Echocardiogram: determine atrial and ventricular size as well as associated valvular defects
Coronary angiography if any ventricular dysfunction or ischaemia suspected
Management of AF is dependent upon the following factors:
- duration of onset:
- < 48 hours;
- > 48 hours.
- systemic symptoms:
- associated illnesses (such as sepsis or myocardial infarction);
- cerebral dysfunction.
- underlying cause.
The acute management of AF is different in a younger patient who has had symptoms for less than 48-hours compared to an older patient with longstanding AF (or unclear onset of AF) with a normal blood pressure and no evidence of decompensation.
- Beta-adrenergic receptor blockers (such as bisoprolol).
- Calcium channel blockers (eg diltiazem)
- Digoxin is not recommended as monotherapy for AF except in sedentary patients, but can be used in addition to beta blockers or calcium channel blockers where symptoms are not controlled. It causes increased contractility and excitability of the myocardial cells. It decreases the propagation and generation of the sino-atrial and atrioventricular nodes and conducting tissues. It is the latter’s vagal effect which is if primary use in AF, by reducing conduction and thereby reducing the ventricular rate. Digoxin is primarily really excreted and hence if there is significant renal impairment, the dose has to be reduced (as well as in the elderly; with hypokalaemia/hypomagnesaemia and hypothyroid patients). The normal loading dose is 500 micrograms and then another repeat dose 6 hours later. Side effects: ectopic ventricular beats; ventricular tachyarrhythmias; supraventricular tachycardias (paroxysmal); vomiting and anorexia; diarrhoea; xanthopsia (yellow vision); photophobia and blurred vision; gynaecomastia.
This is appropriate in patients presenting within 48 hours of the onset of AF, or in those who are not compensating (chest pain, signs of heart failure, low blood pressure)
- Amiodarone, with a loading dose of 300mg intravenously over 1 hour and then 900mg intravenously over the following 23 hours.
- DC (direct current) cardioversion under controlled settings and a general anaesthetic.
Prevention of stroke is a key issue in atrial fibrillation and the most effective method is anti-coagulation. The scoring system to determine if someone should receive anticoagulation is via the CHA2DS2-VASc score:
- C Congestive cardiac failure with dysfunction of the left ventricle (mod-severe) 1
- H Hypertension 1
- A2 Age equal or greater than 75-years 2
- D Diabetes mellitus
- S2 History of stroke or transient ischaemic attack or thromboembolism 2
- V Vascular disease e.g. peripheral vascular disease or history of myocardial infarction 1
- A 65-74 years old 1
- Sc Female (sex) 1
In patients with a score of 2 or above, oral anticoagulation should be offered. This can be with warfarin or one of the Novel Oral Anti-Coagulants (NOACs) (eg dabigatran, rivaroxaban, apixaban)
- Review / Skip
Question 1 of 5
1. Question1 point(s)
Which of the following are causes of atrial fibrillation?CorrectIncorrect
Question 2 of 5
2. Question1 point(s)
Which one of the following scoring systems is used to determine whether anti-coagulation is required?CorrectIncorrect
Question 3 of 5
3. Question1 point(s)
What CHA2DS2VASc index score requires anti-coagulation?CorrectIncorrect
Question 4 of 5
4. Question1 point(s)
Which treatment would you recommend first line for this gentleman as stroke prophylaxis?CorrectIncorrect
Question 5 of 5
5. Question1 point(s)
This gentleman returns to clinic with very severe symptoms from his atrial fibrillation. He is medicated with 10mg bisoprolol and has a pulse of 90 beats per minute (AF). He has been anticoagulated for two months. What would your treatment of choice be to improve his symptoms.CorrectIncorrect