Atrial Fibrillation

Aka: Atrial Fibrillation, Atrial Fib

1. Epidemiology: Incidence
   1. Affects 1 million Americans
   2. Age 60 years: 1.5%
   3. Age 75 years: 9%
2. Definition
   1. Supraventricular Tachycardia with uncoordinated atrial activation and associated atrial contractile dysfunction
3. Causes
   1. 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
4. Pathophysiology
   1. Mechanisms
      1. Enhanced automaticity at depolarizing foci
      2. Reentry via aberrant circuits
   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
5. 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
         2. Drug Abuse (Cocaine, Amphetamines)
         3. Caffeine
   4. Effective methods of terminating prior episodes
      1. Medications (e.g IV Diltiazem)
      2. Cardioversion
      3. Spontaneous resolution
6. Symptoms (Often asymptomatic in young patients - nearly half are without symptoms)
   1. Dyspnea
   2. Dizziness
   3. Palpitations
   4. Acute Fatigue
   5. Acute Congestive Heart Failure exacerbation
7. Labs (esp. for initial episode)
   1. Thyroid Function Test (TSH with reflex to T4 free)
   2. Chemistry panel with electrolytes and Renal Function (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
8. Imaging
   1. Chest XRay
   2. 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)
9. Diagnostics
   1. See Electrocardiogram in Atrial Fibrillation
   2. Review Blood Pressures
   3. Consider stress testing (if specific indications)
10. Management
    1. See Atrial Fibrillation Acute Management
    2. See Atrial Fibrillation Anticoagulation
    3. See Atrial Fibrillation Cardioversion
    4. See Atrial Fibrillation Rate Control
       1. Preferred strategy over Atrial Fibrillation Rhythm Control
       2. Goal Heart Rate: <80 at rest (<110 during Exercise)
11. Management: Interventions
    1. Atrial Fibrillation Ablation
       1. Consider for refractory and paroxysmal Atrial Fibrillation with increased morbidity on medication
       2. Effective at 2 years in 75% of cases
       3. Oral (2003) Circulation 108(19):2355-60
12. Complications
    1. Congestive Heart Failure
    2. Myocardial Infarction
    3. Thromboembolism
13. Prognosis
    1. Mortality: increased two fold over general population
14. References
    1. King (2002) Am Fam Physician 66(2):249-56
    2. Gutierrez (2011) Am Fam Physician 83(1): 61-8