Mechanism:

• Mostly left atrial micro-reentry with changing circuits of excitation
  
• Left atrial dilatation has a favorable effect
  
• Irregular conduction of fibrillation to the AV node

ECG characteristics:

• Irregular fibrillation waves (f) of variable amplitude, configuration, and cycle length
  
• Tachycardia, bradycardia, or normal frequency absolute arrhythmia (irregular intervals between the respective RR intervals) occur dependent of AV conduction capacity

Etiology:

• Cardiac: Hypertensive and coronary heart disease, heart defects (in particular mitral valve defects), carditis, degenerative disease of the impulse conduction system(sinus node syndrome), cardiac surgery
  
• Extracardiac: Hyperthyroidosis, noncardiac surgery, electrolyte shifts, alcohol abuse, infections, pulmonary disease, cerebrovascular event
  
• Primary: No underlying disease demonstrable (lone atrial fibrillation)

Forms:

• Paroxysmal: Always spontaneous conversion to sinus rhythm
  
• Persistent: No spontaneous conversion; however, sinus rhythm can be achieved with medication or electrical conversion
  
• Permanent: Sinus rhythm can be achieved neither with medication nor with electrical conversion

Conversion:

High success rate: LA < 50mm, duration of AF < one year (highest < seven days)

Electrical: External or internal (high success rates)

Medication: Antiarrhythmics of class IA, IC, and III

Alternative: Atrial defibrillator, MAZE operation, catheter ablation

Rhythm Control (medication of first choice):

• Class IC (in combination with beta-blocker): good LV pump function with no CHD
  
• Sotalol: good LV pump function and CHD without myocardial infarction
  
• Amiodarone: impaired LV pump function Class II (beta-blocker)

Rate control:

Medication:

• Beta-blockers (most effective).
  
• Calcium channel blockers (Verapamil, Diltiazem)
  
• Digitalis (Digitoxin, Digoxin)
  
• In rare cases also amiodarone

Alternative:

• AV node ablation with insertion of a pacemaker
  
• AV node modulation with no need for insertion of pacemaker

Prevention of thrombembolism before and after cardioversion:

Acute: Possible without oral anticoagulation up to 48 hours following onset of arrhythmia

Elective: Three weeks of effective oral anticoagulation (INR 2.0–3.0, target 2.5) beforehand: as an exception transesophageal echocardiography is possible to exclude thrombus in LA

After each cardioversion: oral anticoagulation (INR 2.0–3.0, target 2.5) for a minimum of one month – but so longer so better!

Prevention of thrombembolism:

* Prior TIA, systemic embolus or stroke, hypertension, poor LV function, diabetes mellitus, CHD, thrombus in LA, rheumatic mitral-valve disease, prosthetic heart valve – INR 2.0 –3.5!