Key facts:
Authors: Natalie Acors and Peter Glennon
Top Tip: If the ventricular rate cannot be controlled easily, atrial fibrillation is probably not the primary problem - ie find the 'cause'
Key Differential Diagnoses
- Atrial flutter
- Atrial ectopics
Key Investigations
- FBC, ESR, CRP
- U+E, LFT, Bone, Glucose, TFTs ± Troponin T (if suspect MI)
- ECG, CXR
Key Treatment
- PO BISOPROLOL 5 mg od (not if asthmatic), or
- PO/IV DIGOXIN 500 mcg bd 1/7 (if asthmatic, or frail), then 62.5-250 mcg od
- SC ENOXAPARIN 1 mg/kg bd
Key Management Decision
- DC cardioversion (if new, and <24h)
Background
AF is the commonest arrythmia. It is very common, many don't know they have it
Introduction
- Atrial fibrillation is an ineffective, chaotic, irregular, rapid rhythm. The atrial rate is usually 300 beats/min; resulting in irregular ventricular rate, as impulses approach AVN from varying angles, at varying intervals
- The ventricular rate is variable, depending on how may impulses are transmitted to the ventricles, leading to ventricular contraction. So the clinical syndrome can be a bradycardia, or a tachycardia (or a normal heart rate)
- So, to be pedantic, 'Slow' and 'Fast' AF do not really exist as the atrial rate is always fast. Nonetheless, like most clinicians, the authors also use these terms
- To confuse things further, the ventricular rate that can be detected at the apex with a stethoscope (or ECG) is often greater than the rate that can be felt at the radial pulse. It is better, therefore, to report the ventricular rate
- Apart from rate control, anticoagulation is often necessary
- Causes and treatment of atrial flutter are similar. It is not a benign disease; mortality at 1y is 8% in one study
- The CHADS2 Score (see below) has been developed to help you decide whether to anticoagulate or not
Embolisation
- AF is usually associated with enlargement of the left atrium. This results in turbulence and stasis of blood which in turn predisposes to thrombus formation, especially in the atrial appendage
- Apart from heart failure, the most important consequence is that a thrombus may embolise (from the atria) to any part of the peripheral circulation: resulting in a TIA or CVA; or infarction of a major viscus - eg bowel infarction (usually missed, and thus fatal)
- Embolisation from thrombi in the right atrium may result in PE
- So, for these reasons, it is a more serious disease than you would think. Nonetheless, as 2/3rds of patients with AF resolve spontaneously in the first 24 hrs, it is not always essential to act immediately - especially if the patient is well
Definition
- An atrial rhythm, originating from multiple atrial foci
Epidemiology
- > 65 yrs = 5%; >75 yrs = 10%
[Ref]
Note: many don't know they have it, and are missing out on benefits of anticoagulation
Types
- Paroxysmal (50%), Acute or Chronic
- Slow, Controlled or Fast
Note: actually there is no such thing as 'slow' or 'fast' AF, as the atrial rate is always about 300 beats/min. What varies, is the ventricular rate
Causes
Apart from idiopathic ('lone AF'), there are 3 important causes:
- IHD
- Hyperthyroidism
- Mitral valve disease
There are many others (pulmonary disease, BP, cardiomyopathy; alcohol is important cause in <60 yrs)
Note: it is not clear whether 'lone AF' in an asymptomatic patient is a disease (see prognosis; but there is little evidence that anticoagulation is of any benefit). In Lone AF the heart is structurally normal, and no cause can be found
Symptoms
- Very variable
- May be asymptomatic, or have symptoms of heart failure (SOB etc)
- If slow (AV block), collapse
- If fast, collapse ± fast irregular palpitations
- Or complication (CVA, or abdominal pain in bowel ischaemia)
Note: heart failure or an embolic complication these can be the presentation of AF
Key questions
- "When did the symptoms start?"
- "Have you had a CVA or TIA before?" (risk stratification)
- "Do you have high blood pressure and have you ever been a heavy drinker (of alcohol)?"
Signs
- Very variable
- May be none, or have signs of heart failure
- Irregularly irregular pulse
- Absent 'a' wave in JVP
- Murmur associated with underlying disease (eg, MS or MR); look for endocarditis
- Or complication (CVA, abdominal tenderness in bowel ischaemia)
Investigation
Blood
- FBC, CRP
- U+E, LFT, Bone, Glucose, TFTs (?cause)
- ± Troponin T (if MI?)
- ± BC (if suspect infective endocarditis)
Other
- CXR
- ECG
Specialist investigation
- ECHO
Differential diagnosis
- Other causes of an irregularly irregular pulse:
- Atrial or ventricular ectopics
- Atrial flutter with variable block
Treatment
The three therapeutic goals in AF are: cardioversion (if possible), control of ventricular rate (if not) and the prevention of thromboembolism
Treatment atrial fibrillation
(first line)
Drugs
- May not need any, if rate controlled
- PO BISOPROLOL 5 mg od (not if asthmatic), or
- PO/IV DIGOXIN 500 mcg bd 1/7 (if asthmatic, or frail), then 62.5-250 mcg od (depending on frailty and renal function)
[Ref] - SC ENOXAPARIN 1 mg/kg bd
- ± PO/IV FUROSEMIDE 40-80 mg od (80mg if creatinine > 200), if has fluid overload
Later
- PO WARFARIN 3 mg od (or PO ASPIRIN 75 mg od, if risks of WARFARIN too high)
Note: the use of anticoagulation is debated in AF. This and other AF controversies are discussed in:
[Ref]
Procedures
- IV
- ECG monitoring
- OXYGEN, if hypoxic
- Sit up, if heart failure [Ref]
Indications for WARFARIN
- This is a controversial area. The dangers of warfarin are probably outweighed by its benefits (mainly CVA prevention) if the patient has CCF, DM, structural heart disease, BP, prev CVA/TIA, or is >75y (see NICE guidelines in references)
- The CHADS2 score has been developed to help:
C CCF = 1 point
H Hypertension = 1 point
A Age > 75 yrs = 1 point
D DM = 1 point
S2 Stroke (prev CVA or TIA) = 2 points - If CHADS2 0 no warfarin; if 1-2 aspirin or warfarin; if 3+ warfarin
Key management decision
- DC cardioversion/not
Stop
- Antiarrthymic, if thought to be cause (specialist decision)
Treatment
(second line)
- IV AMIODARONE 5 mg/kg over 20-120 mins, via central line, with ECG monitoring; max 1.2g over 24h
- DC cardioversion
Note: if AF new and acute, and recent, DC cardioversion may be attempted before drugs
Prescribing issues
- Loading dose of DIGOXIN same; but reduce maintenance dose in frail/elderly or renal failure (to 125 mcg or 62.5 mcg od)
Rhythm vs Rate Control
- Another controversial area. There is an ongoing debate about the relative importance of reverting the rhythm to sinus (rhythm control) or controlling the ventricular rate (rate control)
- If the AF is of <48 hrs duration, the benefits of trying to revert it to SR (say with DC cardioversion) probably outweigh the risks of lifelong warfarin etc
Admit?
- Usually, though if patient not in heart failure, OP management possible
Bed plan?
- Medical admission ward, if uncomplicated
- Cardiology, if complicated
Referrals
Medical
- Cardiology, if complicated
Other
- Anticoagulant clinic (on discharge)
The Rest
2/3rds acute AF resolves spontaneously on first 24 hrs - ie sometimes it is better to do nothing, and wait
Complications
- Acute heart failure (rarely the cause)
- CVA
- Other emboli events (bowel, PE)
Prognosis
- Mortality at 1y is 8% in one study
- 2/3rds acute AF resolves spontaneously on first 24 hrs
- In a follow-up of the Framingham study, chronic AF was independently associated with 50-90% increase in mortality
- Compared to controls, the risk of CVA is: 17.6x, if there is a rheumatic cause; 5.6x for non-rheumatic; and 4x for lone AF
Note: ie, it is a serious disease
Risk stratification, CVA (adapted from NICE, 06)
High
- Previous ischaemic CVA/TIA, or thromboembolic event
- Age >= 75 yrs with BP, DM, or vascular disease (IHD, PVD)
- Clinical evidence of valve disease or heart failure, or impaired LV function on ECHO (not needed for routine assessment)
Moderate
- > 65 yrs with no high risk factors
- < 75 yrs with BP, DM, or vascular disease (IHD, PVD)
Low
- < 65 yrs with no moderate or high risk factors
2° Prevention + Health promotion
- Stay on warfarin (or aspirin, in frail elderly, or if patient has PH of Upper GI bleed), for life
- Attend anticoagulant clinic reliably
- Be aware of warfarin interactions (especially alcohol)
- (If thought to be cause) avoid alcohol, caffeine
Don't forget
- Look for underlying cause
- Exclude hyperthyroidism, and MI
- 2/3rds resolve spontaneously - ie may be better to do nothing and wait
- Paroxysmal atrial fibrillation often does not need treatment immediately
- Make anticoagulant clinic appointment
Red flags
- Heart failure
- Cardiogenic shock
- Rate not controlled at 48h
