EKG

Atrial Fibrillation

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Atrial Fibrillation, Atrial Fib

  1. Most common arrhythmia
  2. Affects 2.3 million people in the United States
  3. Prevalence increases with age
    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
  • Definition
  1. Supraventricular Tachycardia with uncoordinated atrial activation and associated atrial contractile dysfunction
  • 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
  • Pathophysiology
  1. Mechanisms
    1. 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. Reentry via small aberrant circuits that spontaneously arise in atria
  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
  • 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
  • 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)
  • Symptoms
  1. Often asymptomatic (21% overall, and 50% in younger patients)
  2. Acute Fatigue
  3. Palpitations
    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
    1. Suggests underlying Coronary Artery Disease
  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
  • Signs
  • Cardiovascular
  1. Pulse irregular
    1. Test Sensitivity: 94%
    2. Test Specificity: 72%
  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)
  • 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
    2. Event Monitor
  3. Evaluation for underlying Coronary Artery Disease if symptoms suggest (not typically the cause)
    1. Stress testing (e.g. Stress Echocardiogram, Stress Cardiolite)
  • 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
    2. Brain Natriuretic Peptide (BNP)
    3. D-Dimer
  • 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
  • Management
  • Chronic
  1. General measures
    1. Review Blood Pressures
    2. Consider stress testing (if specific indications)
  2. Medication Management (3 strategies)
    1. 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)
    2. Other strategies
      1. Atrial Fibrillation Rhythm Control
      2. Episodic Atrial Fibrillation Home Management
    3. Efficacy
      1. Best chance of maintaining sinus rhythm is age <65 years with structurally normal heart
  3. 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
    4. Oral (2003) Circulation 108(19):2355-60 [PubMed]
  4. Invasive surgical procedures (high risk)
    1. MAZE Procedure (open surgical procedure replaced in most cases by ablation as above)
    2. Left atrial appendage isolation (LAA Obliteration)
      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
      3. May be replaced in future by percutaneous placed LAA Occlusion devices (e.g. watchman, Amplatzer)
        1. Not approved for use in U.S. as of 2016
  • Complications
  1. Congestive Heart Failure
  2. Myocardial Infarction
  3. Cerebrovascular Accident
    1. Due to Thromboembolism (often formed within atrial appendage)
    2. Atrial Fibrillation is associated with a 5 fold increased CVA risk
    3. Risk increases with higher CHADS2-VASc Score
  • Prognosis
  1. Mortality: Increased up to two fold over the general population