A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Overview

References:

National Guidelines
Review

Atrial Fibrillation

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: 1. IHD 2. Hyperthyroidism 3. 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
Key investigation	ECG AF ECG (with lateral ischaemia)
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 1.2 g 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

The Rest

2/3^rds 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 1. Previous ischaemic CVA/TIA, or thromboembolic event 2. Age >= 75 yrs with BP, DM, or vascular disease (IHD, PVD) 3. Clinical evidence of valve disease or heart failure, or impaired LV function on ECHO (not needed for routine assessment) Moderate 1. > 65 yrs with no high risk factors 2. < 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

References

national guidelines

UK/SIGN: Cardiac arrhythmias in coronary heart disease, 2007 (pdf)

UK/NICE: AF: The management of AF, 2006

review

Management of AF. Lip GYH et al. Lancet; 370: 604–18, 2007 (pdf)

Management of Atrial Fibrillation: Review of the Evidence for the Role of Pharmacologic Therapy, Electrical Cardioversion, and Echocardiography. McNamara RL et al. Ann Intern Med; 139 (12): 1018-1033, 2003

Acute Management of Atrial Fibrillation: Part I. Rate and Rhythm Control. King EK et al. Am Fam Physician; 66: 249-56, 2002

Prognosis, disease progression, and treatment of atrial fibrillation patients during 1 year: follow-up of the Euro Heart Survey on Atrial Fibrillation. Nieuwlaat R et al. European Heart Journal; 29(9): 1181-1189, 2008