Atrial Fibrillation

Aka: Atrial Fibrillation, Atrial Fib

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II. Epidemiology: Prevalence

  1. Most common Arrhythmia seen in adult primary care
  2. Affects 3 to 6 million adults in the United States
  3. Prevalence increases with age (esp. age >50 years)
    1. Age 60 years: 1.5%
    2. Age 75 years: 9%
  4. Complications
    1. Primary cause of 30,000 to 40,000/year Cerebrovascular Accidents in the United States

III. Definitions

  1. Atrial Fibrillation
    1. Supraventricular Tachycardia with uncoordinated atrial activation and associated atrial contractile dysfunction

IV. Causes

  1. See Atrial Fibrillation Causes
  2. Atrial Fibrillation cause impacts risk of complications
    1. Valvular Atrial Fibrillation (e.g. mitral valve disorder) stroke risk: 17 fold increased risk
    2. Non-valvular Atrial Fibrillation stroke risk: 5 fold increased risk

V. Pathophysiology

  1. Mechanisms
    1. Reentry via small aberrant circuits that spontaneously arise in atria (associated with interstitial fibrosis) OR
    2. Enhanced automaticity at depolarizing foci
      1. Multiple small simultaneously wavelets arise and propagate
      2. May result from repeatedly firing Premature Atrial Contractions (PACs)
        1. Arise near origin of pulmonary veins at the left atrium
  2. Initial Consequences: Acute Atrial Remodeling
    1. Patchy fibrosis
    2. Collagen deposition
    3. Sinoatrial Node fatty deposition
    4. Ion channel and depolarization changes
  3. Later Consequences: Chronic Atrial Remodeling
    1. Longterm Atrial Fibrillation results in atrial enlargement (irreversible)
    2. Possibility of restoring to normal sinus rhythm becomes less likely over time
  4. Functional Consequences: Atrial contractions are uncoordinated
    1. Rapid ventricular response
      1. Tachycardia and diminished diastolic filling decrease Cardiac Output
      2. Coronary circulation compromised and Cardiomyopathy increase morbidity and mortality
    2. Blood stasis and atrial clot forms
      1. Results in increased Thromboembolism and Cerebrovascular Accident risk
    3. Reduced Ventricular Filling (absent "Atrial Kick")
      1. Ventricular diastolic filling is primarily driven by a suction effect rather than atrial contraction
      2. However, with increased activity, the atrial contraction becomes more important to Cardiac Output

VI. Types

  1. Acute Atrial Fibrillation
    1. New onset or recurrent Atrial Fibrillation lasting <48 hours
  2. Paroxysmal Atrial Fibrillation
    1. New or recurrent Atrial Fibrillation lasting <7 days and spontaneously resolves (self-terminates)
    2. Carries the same longterm CVA risk as persistent Atrial Fibrillation
  3. Persistent Atrial Fibrillation
    1. New or recurrent Atrial Fibrillation lasting >7 days and does not spontaneously resolve or self-terminate
    2. Results in cardiac remodeling (see above) and less likelihood overtime of restoring sinus rhythm
  4. Secondary Atrial Fibrillation
    1. Due to acute secondary cause
    2. Examples: MI, PE, Pericarditis, Myocarditis, Hyperthyroidism, Pneumonia
    3. Atrial Fibrillation expected to resolve after treatment of secondary cause
  5. Lone Atrial Fibrillation
    1. Atrial Fibrillation in age <60 years without underlying cardiopulmonary disease (associated with better prognosis)
  6. Atrial Fibrillation with Rapid Ventricular Response (RVR)
    1. Heart Rate >100 beats/min at rest (or >110 beats/min on light activity)
  7. Atrial Flutter
    1. See Atrial Flutter (includes 2 subtypes based on Atrial Flutter rate)
    2. Closely related to Atrial Fibrillation and often co-occurs in the same patient (even on the same EKG)
    3. Constant atrial rate, with a fixed ratio of A:V rate (1:1 of 300 bpm, 2:1 of 150 bpm, 3:1 of 90 bpm, 4:1 of 75 bpm)
    4. Treated identically to Atrial Fibrillation, but Atrial Flutter is easier to cardiovert and harder to rate control

VII. History

  1. Onset of current episode of Atrial Fibrillation
  2. Frequency of Atrial Fibrillation
    1. First episode
    2. Paroxysmal
    3. Persistent or chronic
  3. Precipitating factors or triggers of current episode
    1. See Atrial Fibrillation Causes
    2. Exacerbation of chronic disease
      1. Coronary Artery Disease (CAD)
      2. Congestive Heart Failure (CHF)
      3. Chronic Obstructive Pulmonary Disease (COPD)
      4. Hypertension
      5. Thyroid Disorder
    3. Substances
      1. Alcohol Abuse (most common)
      2. Drug Abuse (Cocaine, Amphetamines)
      3. Caffeine
  4. Effective methods of terminating prior episodes
    1. Medications (e.g IV Diltiazem, Lopressor)
    2. Cardioversion
    3. Spontaneous resolution (paroxysmal Atrial Fibrillation)

VIII. Symptoms

  1. Often asymptomatic (21% overall, and 50% in younger patients)
  2. Acute Fatigue
  3. Palpitations (33% of cases)
    1. Abrupt onset and termination suggests supraventricular tachyarrhythmi
    2. Contrast with gradual onset of Sinus Tachycardia
    3. Associated with the irregular ventricular response
  4. Angina or Chest Pain
    1. Suggests underlying Coronary Artery Disease or demand ischemia related to rapid ventricular rate
  5. Dyspnea or Orthopnea
    1. May suggest underlying cardiac disease or secondary pulmonary cause (e.g. Pulmonary Embolism, COPD)
    2. Consider decompensation with Systolic Heart Failure (see below)
  6. Acute Congestive Heart Failure exacerbation
    1. Symptoms are related to decreased Cardiac Output (from loss of atrial kick or rapid ventricular rate)
  7. Dizziness
    1. True Syncope (as opposed to Dizziness) is more often associated with ventricular Arrhythmia
  8. Findings of instability related to rapid ventricular rate (at very high rates)
    1. Hypotension or Syncope
    2. Congestive Heart Failure
    3. Myocardial Ischemia

IX. Signs: Cardiovascular

  1. Pulse irregularly irregular
    1. Test Sensitivity: 92 to 94%
    2. Test Specificity: 72 to 82%
  2. Jugular Venous Pulsations irregular
  3. First Heart Sound may have variable amplitude
  4. Cardiac murmur may suggest underlying valvular heart disease
  5. Acute Congestive Heart Failure signs (e.g. rales, S3 gallup, Jugular Venous Distention)

X. Diagnostics

  1. Electrocardiogram
    1. See Electrocardiogram in Atrial Fibrillation
    2. No discrete atrial activity (Discrete P Waves absent)
    3. Atrial Fibrillation waves (F Waves) seen as small irregular waves at rate >150/min
    4. Irregularly irregular ventricular rhythm
      1. Inconsistent R-R interval, with rates up to rapid rate up to 160-200 bpm in RVR
  2. Other rhythm evaluation in suspected paroxysmal Atrial Fibrillation
    1. Holter Monitor or Zio Monitor
    2. Event Monitor
    3. Loop recorders
    4. Wrist watches (Apple Watch)
  3. Evaluation for underlying Coronary Artery Disease if symptoms suggest (not typically the cause)
    1. Stress testing (e.g. Stress Echocardiogram, Stress Cardiolite)

XI. Labs (esp. for initial episode)

  1. Thyroid Function Test (TSH with reflex to T4 free)
  2. Chemistry panel with Electrolytes and Renal Function tests (basic metabolic panel)
  3. Complete Blood Count (CBC)
  4. Other tests that are not indicated unless specific findings
    1. Troponin I or Troponin T
    2. Brain Natriuretic Peptide (BNP)
    3. D-Dimer

XII. Imaging

  1. Chest XRay
    1. Assess for cardiac disease
      1. Cardiomegaly
      2. Congestive Heart Failure
    2. Assess for pulmonary disease
      1. Pulmonary fibrosis
      2. COPD Xray changes
      3. Pneumonia
  2. Transthoracic Echocardiogram (TEE if early cardioversion pursued)
    1. Indicated in all patients with new onset Atrial Fibrillation
    2. Assess left and right atrial size
    3. Assess ejection fraction
    4. Assess Left Ventricular Hypertrophy
    5. Observe for valvular disease
    6. Assess for Pulmonary Hypertension (peak RV pressure)
      1. May suggest Pulmonary Embolism or other pulmonary disease

XIII. Management: Acute

  1. See Atrial Fibrillation Acute Management
  2. See Atrial Fibrillation Anticoagulation
  3. Atrial Fibrillation Cardioversion
    1. See Electrical Synchronized Cardioversion of Atrial Fibrillation
      1. See Synchronized Cardioversion
      2. See Conscious Sedation
    2. See Atrial Fibrillation Pharmacologic Cardioversion
      1. See Ottawa Aggressive Protocol in Atrial Fibrillation Cardioversion

XIV. Management: Chronic

  1. Lifestyle Changes to reduce Atrial Fibrillation Risk
    1. Ask about sleep disordered breathing (Obstructive Sleep Apnea symptoms)
    2. Smoking Cessation
    3. Alcohol abstinence
    4. Moderate Exercise (3.5 hours/week) IS recommended
      1. Moderate Exercise decreases Atrial Fibrillation frequency and burden
      2. However, high volume Exercise (>3 hours/day) may increase Atrial Fibrillation risk
    5. Caffeine abstinence is NOT needed
      1. Typical Caffeine use does not appear to affect Atrial Fibrillation frequency
  2. Hypertension Management
    1. Review Blood Pressures
    2. Hypertension is the most important modifiable risk factor for Atrial Fibrillation risk
    3. Target systolic Blood Pressure <140 mmHg
  3. Anticoagulation for Stroke Prevention
    1. See Atrial Fibrillation Anticoagulation
    2. See CHADS2-VASc Score
    3. Atrial Fibrillation is assumed responsible for a majority of the 25% of strokes that are cryptogenic
    4. Anticoagulation is indicated in CHADS2-VASc Score >=2 in men (>=3 in women)
      1. DOACs are preferred for Atrial Fibrillation Anticoagulation in most patients
      2. Warfarin is recommended in significant Mitral Stenosis or with Mechanical Heart Valves
  4. Medication Management of Atrial Fibrillation Rhythm and Rate Control (3 strategies)
    1. See Atrial Fibrillation Rate Control
    2. See Atrial Fibrillation Rhythm Control
    3. Atrial Fibrillation Rate Control (preferred in most cases)
      1. Preferred strategy over Atrial Fibrillation Rhythm Control
      2. Goal Heart Rate: <80 at rest (<110 during Exercise)
    4. Other strategies
      1. Atrial Fibrillation Rhythm Control
      2. Episodic Atrial Fibrillation Home Management
    5. Efficacy
      1. Best chance of maintaining sinus rhythm is age <65 years with structurally normal heart
  5. Atrial Fibrillation Ablation
    1. See Cardiac Catheter Ablation
    2. Consider for refractory and paroxysmal Atrial Fibrillation with increased morbidity on medication
    3. Effective at 2 years in 75% of cases (but Atrial Fibrillation recurrs in up to 40% of ablation patients)
    4. Anticoagulation is continued for at least 3 months after catheter ablation
    5. Oral (2003) Circulation 108(19):2355-60 [PubMed]
  6. Invasive surgical procedures
    1. MAZE Procedure
      1. Open surgical procedure replaced in most cases by catheter ablation as above
    2. Left Atrial Appendage Closure Device (e.g. Watchman Device, Amplatzer)
      1. Reduces stroke risk by removal or ligation of the left atrial appendage (source 90% of emboli)
      2. Decreases stroke risk, but does not affect underlying Atrial Fibrillation
        1. Also decreases cardiovascular and all-cause mortality
      3. Consider in perioperative cardiac surgery patients
        1. Decreases perioperative stroke risk and all-cause mortality

XV. Complications

  1. Congestive Heart Failure
  2. Myocardial Infarction
  3. Cerebrovascular Accident
    1. Due to Thromboembolism
      1. Typically form in the left atrial appendage (hence LAA Obliteration procedure)
    2. Atrial Fibrillation is associated with a 5 fold increased CVA risk
    3. Risk increases with higher CHADS2-VASc Score

XVI. Prognosis

  1. Mortality: Increased up to two fold over the general population

XVII. References

  1. Casaletto (2014) Crit Dec Emerg Med 28(4): 10-19
  2. King (2002) Am Fam Physician 66(2):249-56 [PubMed]
  3. Gutierrez (2017) Am Fam Physician 83(1): 61-8 [PubMed]
  4. Gutierrez (2011) Am Fam Physician 94(6): 442-52 [PubMed]
  5. Holder (2024) Am Fam Physician 109(5): 398-404 [PubMed]
  6. Joglar (2024) Circulation 149(1):e1-e156 +PMID: 38033089 [PubMed]
  7. Stiell (2011) Canadian J Cardiol 27(1): 38-46 [PubMed]
  8. Wann (2011) Circulation 123(1): 104-23 [PubMed]

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Related Studies

Ontology: Atrial Fibrillation (C0004238)

Definition (CHV) rapid tremor and shake of upper chambers of the heart
Definition (CHV) rapid tremor and shake of upper chambers of the heart
Definition (CHV) rapid tremor and shake of upper chambers of the heart
Definition (CHV) rapid tremor and shake of upper chambers of the heart
Definition (CHV) rapid tremor and shake of upper chambers of the heart
Definition (CHV) rapid tremor and shake of upper chambers of the heart
Definition (MEDLINEPLUS)

An arrhythmia is a problem with the speed or rhythm of the heartbeat. Atrial fibrillation (AF) is the most common type of arrhythmia. The cause is a disorder in the heart's electrical system.

Often, people who have AF may not even feel symptoms. But you may feel

  • Palpitations -- an abnormal rapid heartbeat
  • Shortness of breath
  • Weakness or difficulty exercising
  • Chest pain
  • Dizziness or fainting
  • Fatigue
  • Confusion

AF can lead to an increased risk of stroke. In many patients, it can also cause chest pain, heart attack, or heart failure.

Doctors diagnose AF using family and medical history, a physical exam, and a test called an electrocardiogram (EKG), which looks at the electrical waves your heart makes. Treatments include medicines and procedures to restore normal rhythm.

NIH: National Heart, Lung, and Blood Institute
Definition (NCI_CTCAE) A disorder characterized by a dysrhythmia without discernible P waves and an irregular ventricular response due to multiple reentry circuits. The rhythm disturbance originates above the ventricles.
Definition (NCI_FDA) An arrhythmia in which minute areas of the atrial myocardium are in various uncoordinated stages of depolarization and repolarization; instead of intermittently contracting, the atria quiver continuously in a chaotic pattern, causing a totally irregular, often rapid ventricular rate.
Definition (NCI) A disorder characterized by an electrocardiographic finding of a supraventricular arrhythmia characterized by the replacement of consistent P waves by rapid oscillations or fibrillatory waves that vary in size, shape and timing and are accompanied by an irregular ventricular response. (CDISC)
Definition (CSP) disorder of cardiac rhythm characterized by rapid, irregular atrial impulses and ineffective atrial contractions.
Definition (MSH) Abnormal cardiac rhythm that is characterized by rapid, uncoordinated firing of electrical impulses in the upper chambers of the heart (HEART ATRIA). In such case, blood cannot be effectively pumped into the lower chambers of the heart (HEART VENTRICLES). It is caused by abnormal impulse generation.
Concepts Pathologic Function (T046)
MSH D001281
ICD9 427.31
SnomedCT 155364009, 266306001, 49436004
LNC LA17084-7
English Atrial Fibrillations, Auricular Fibrillation, Auricular Fibrillations, Fibrillations, Atrial, Fibrillations, Auricular, FIBRILLATION ATRIAL, AURICULAR FIBRILLATION, Auricular fibrillation, Fibrillation, Atrial, Fibrillation, Auricular, AF, atrial fibrillation, atrial fibrillation (diagnosis), Afib, AFib, Fibrillation atrial, Atrial Fibrillation [Disease/Finding], Fibrillation;atrial, afib, atrial fibrillation (AF), auricular fibrillations, atrial fibrillations, Familial Atrial Fibrillation, Fibrillation - atrial, ATRIAL FIBRILLATION, Atrial fibrillation, AF - Atrial fibrillation, Atrial fibrillation (disorder), atrium; fibrillation, auricular; fibrillation, fibrillation; atrial or auricular, Atrial Fibrillation, auricular fibrillation
French FIBRILLATION AURICULAIRE, FA, AFib, Fibrillation auriculaire, Fibrillation atriale
German VORHOFFLIMMERN, AF, Afib, Flimmern Vorhof, Herzohrflimmern, HERZVORHOFFLIMMERN, Vorhofflimmern, Aurikuläres Flimmern
Portuguese FIBRILACAO AURICULAR, FA, FIBRILHACAO AURICULAR, Fibrilhação auricular, Fibrilação Atrial, Fibrilação Auricular
Spanish FIBRILACION AURICULAR, FA, Fibrilación atrial, AURICULAR, FIBRILACION, fibrilación auricular (trastorno), fibrilación auricular, Fibrilación auricular, Fibrilación Atrial, Fibrilación Auricular
Dutch AFib, AF, atriumfibrillatie, hartoorfibrilleren, atrium; fibrilleren, auriculair; fibrilleren, fibrilleren; atrium of auriculair, atriale fibrillatie, Atriumfibrillatie, Boezemfibrillatie, Fibrillatie, atrium-, Fibrillatie, boezem-, Fibrilleren, boezem-
Swedish Förmaksflimmer
Japanese ｼﾝﾎﾞｳｻｲﾄﾞｳ, 心房細動, 心房性細動
Finnish Eteisvärinä
Russian USHKA PREDSERDIIA FIBRILLIATSIIA, PREDSERDII FIBRILLIATSIIA, ПРЕДСЕРДИЙ ФИБРИЛЛЯЦИЯ, УШКА ПРЕДСЕРДИЯ ФИБРИЛЛЯЦИЯ
Czech Fibrilace ouška, Fibrilace síní, fibrilace síní, síňová fibrilace, FiS
Italian Fibrillazione auricolare, Fibrillazione atriale
Croatian ATRIJ, FIBRILACIJA
Polish Migotanie przedsionków
Hungarian AFib, Fibrillatio atrialis, Pitvarfibrillatio
Norwegian Forkammerflimmer, Hjerteflimmer, Artrieflimmer
Derived from the NIH UMLS (Unified Medical Language System)

Related Topics in Electrocardiogram

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