page sections

introduction
the case of Tony L
causes and risk factors
pathophysiology
signs and symptoms
investigations
differential diagnosis
treatments
consequences and course
additional resources
topic development

Atrial Fibrillation and Flutter

last authored: March 2011, David LaPierre
last reviewed:

NOTE: IN DEVELOPMENT

Introduction

Atrial fibrillation (AF) is a common heart arrhythmia in which the atria contract chaotically and often very rapidly. As many of these beats are conducted through the heart, the ventricular rhythm can also be quite fast, often up to 140-160. AF is caused by changes in the heart's structure or electrical conductance, such that abnormal impulses form and are transmitted across the heart.

AF may be classified according to it's duration:

paroxysmal: self-limited, or treated, lasting less than 7 days
persistent: lasting more than 7 days
longstanding: lasting more than 12 months
permanent: a decision not to attempt reversal of rhythm

AF can be asymtomatic, or it can be serious. Rapid ventricular rates can decrease cardiac output, leading to shortness of breath, presyncope, fatigue, and poor functional status. Severe symptoms include angina, syncope.

Atrial thrombi often form, particularly in the left atrial appendage, posing risk for emobolus and infarction, most ominously in the brain as a stroke. Up to 15% of strokes are caused by AF, which leads to a 3-5 fold increase in stroke (ref). Lastly, in patients with electrical conductance problems, AF can lead to a rapid ventricular tachycardia that can end in ventricular fibrillation and death. Mortality doubles in age-matched people.

AF is extremely common; over 20% of people over 40 will develop it. AF affects 5% of people over 70, 10% of people over 80%.

Atrial flutter is characterized by regular atrial activity at a rate of 180-350 bpm. Many of these beats fall during the ventricular refractory period, resulting in a much slower ventricular heart rate. A fixed block (2:1 or 4:1) can result in a regular ventricular rate of 300, 150, 100, 75, or 60.

The Case of Tony L

Tony is a 86 year-old man who comes to you with palpitations that have been present for 2 days. He is otherwise asymptomatic. You check his pulse, and his rate is 134 and irregular.

is this atrial fibrillation?
what do you do?

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Causes and Risk Factors

There are a variety of factors that can contribute to the development of AF.

Aging, hypertension, and heart disease are the most common causes.

It is important to first assess for reversible causes:

alcohol
caffeine
hyperthyroidism
sleep apnea
obesity
smoking

Other risk factors include:

male sex
valvular heart disease
coronary artery disease
acute myocardial infarction
pulmonary embolus
cardiomyopathy
sick sinus syndrome: ECG diagnosis (sinus bradycardia, sinus arrest, tachyarrhytmia)
cardiac surgery
pericarditis: viral, tumour infiltration
WPW: Wolff-Parkinson-White syndrome: accessory bundle
lung cancer
idiopathic

Atrial flutter is typically caused by a large rentry circuit. It generally occurs following heart disease, and can be transient, persistent, or permanent.

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Pathophysiology

Atrial fibrillation frequently follows atrial fibrosis, stretching, or injury. This can occur with hypertension, heart failure, or mitral stenosis.

The sino-atrial (SA) node can become fibrotic or sclerotic, and the atrioventricular (AV) node will only allow so many beats through.

Atrial ectopy can trigger fribrillation, using triggered or automatic. An abnormal atrium, scarred and stretched, is easily put into fibrillation by triggers, due to easy reentry.

Cardiac output can decrease with the increased ventricular rate, and cardiac ischemia can also result due to the increased metabolic demand. Atrial fibrillation can also lead to blood clots forming in the poorly contracting atria. These clots can leave the heart and cause strokes and other types of ischemic disease in the body.

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Signs and Symptoms

history
physical exam

History

Some people with AF can be asymptomatic, while may become unstable. Symptoms can include:

palpitations
fatigue
dyspnea
lightheadedness/pre-syncope/syncope
chest pain/angina (if with coronary artery disease)
symptoms of congestive heart failure ( especially if with valvular disease)

Symptoms of stroke can follow embolus with AF.

Physical Exam

An irregularly irregular, rapid pulse is the classic finding with atrial fibrillation.

Other signs include:

variable first heart sound
variable systolic blood pressure
absent a wave on JVP

Assess heart rate at heart apex, as some beats will not be palpable at the wrist.

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Investigations

lab investigations
diagnostic imaging

Lab Investigations

TSH is helpful to screen for hyperthyroidism.

If warranted, troponin may be added to assess for ischemia.

INR/PT is necessary for patients who will be treated with warfarin.

Diagnostic Imaging

EKG is diagnostic, revealing fibrillations without P waves. QRS complexes are often irregularly irregular. It is difficult to diagnose exactly how long AF must be present to pose a risk, but American and European guidelines suggest at least 30 seconds.

ECG findings of atrial flutter includes:

P waves with a sinusoidal or sawtooth appearance.

A stress test can be used to exacerbate abnormal rhythms. A 24-hour Holter monitor can be used to assess response to medication. A loop monitor can be useful for symptoms that occur a few times monthly.

Chest X ray may detect cardiomyopathy.

CT with pulmonary angiography, or ventilation-perfusion scan, can be done if pulmonary embolus is suspected.

Echocardiography can detect valvular heart disease or heart failure.

Transesophageal echo can be done to identify atrial thrombus if cardioversion is planned.

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Differential Diagnosis

The differential includes:

multifocal atrial tachycardia
sinus tachycardia with frequent premature atrial beats

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Treatments

Treatment depends on clinical condition, underlying disease, desire for rhythm vs rate control, and risk of stroke. Ensure emergency assessment and resuscitation occurs promptly.

Once the situation allows it, endeavour to treat the offending cause(s) as identified.

AFFIRM 2002:

There is ongoing debate regarding the relative value of rate vs rhythm control. Outcomes appear quite similar

Rhythm control (cardioversion + antiarrhytmics) vs rate control (beta blocker plus digoxin). Very similar, but rate control appeared better.

Atrial flutter is normally treated with electrical cardioversion, as it responds poorly to medication.

resuscitation
rate control
rhythm control
anticoagulation
electrical ablation

Resuscitation

Atrial fibrillation can be a medical emergency. As the situation warrants, provide oxygen, ensure IV access x2, and attach a monitor.

If the patient is unstable, with hypotension, altered mental status, chest pain, or evidence of heart failure, cardioversion is warranted. Consider procedural sedation as appropriate.

Some clinicians utilize heparin IV during emergent cardioversion.

If the rate is very fast - 250 or 300 bpm - and the QRS complex is wide, be concerned for AF complicating WPW. Aggressively use cardioversion to convert the rhythm, and avoid AV nodal blocking medications, which can rapidly lead to VF.

Consider vasopressors as needed to stabilize the BP if hypotension is persistent.

Consider beginning medications such as amiodarone or diltiazem as you attempt cardioversion.

Rate Control

Rate control is an acceptable treatment in many cases, with a target heart rate of 100, or 110 if there is no evidence of left ventricular dysfunction and the patient remains asymptomatic.

Medications to consider, either IV or PO, include:

beta blockers: propanalol, metoprolol, atenolol, nadalol
non-dihydropyridine calcium channel blockers (verapamil, diltiazem)
digoxin in the elderly
amiodarone, more acute

Rhythm control

main articles: cardioversion antiarrhythmics

Rhythm control may involve either electrical or pharmacological cardioversion. Many patients prefer this approach, as it can lead to a resolution of the AF and a return to sinus rhythm.

Elective cardioversion may be considered if AF has been present for less than 48 hours. Ensure the history is very clear in determining this 48 hour time frame.

If AF has been present for >48 hours, cardioversion should not be done until systemic anticoagulation has been given for at least three weeks, with consistent therapeutic use. Anticoagulation should be given for at least one month after cardioversion.

Electrical cardioversion is an option in the emergency department or hospital setting, especially within 48 hours of onset.

Pharmacological cardioversion, may also be considered with antiarrhythmics such as amiodorone, propafenone, flecainide, dofetilide, and ibutilide.

These medications often are required over the longer term to maintain rhythm; however, these medications can have serious side effects limiting their use.

Anticoagulation

All patients with atrial fibrillation should be on anticoagulation, but the specific medication depends on risk of stroke, risk of bleeding, and patient preferences.

One of the most widely promoted algorithms for calculating stroke risk is CHA₂DS₂-VASc (ref). It assigns scores of 1 or 2 to the following risk factors:

Risk factors