What are the different subtypes of atrial fibrillation?

Subtypes of Atrial Fibrillation

Atrial fibrillation (AF) is classified into several distinct subtypes based on episode duration, including paroxysmal AF (episodes terminating spontaneously or with intervention within 7 days), persistent AF (continuous AF sustained >7 days), long-standing persistent AF (continuous AF >12 months), and permanent AF (when patient and clinician jointly decide to stop further attempts to restore/maintain sinus rhythm). 1

Primary Classification System

The American College of Cardiology/American Heart Association/Heart Rhythm Society guidelines classify AF into the following subtypes:

1. Paroxysmal AF

   • Episodes that terminate spontaneously or with intervention within 7 days
   • Episodes may recur with variable frequency
   • Often self-terminating within 24 hours 1, 2

2. Persistent AF

   • Continuous AF sustained for more than 7 days
   • Requires intervention such as cardioversion for termination 1, 2

3. Long-standing Persistent AF

   • Continuous AF lasting more than 12 months
   • Rhythm control is still considered a treatment option 1, 2

4. Permanent AF

   • Term used when patient and clinician jointly decide to stop further attempts to restore/maintain sinus rhythm
   • Represents a therapeutic attitude rather than an inherent pathophysiological attribute 1, 2

Additional Classification Categories

Beyond the primary temporal pattern-based classification, other important categories include:

• First-diagnosed AF: Initial presentation of AF, regardless of duration or symptoms 2

• Lone AF: A historical descriptor typically applied to younger patients (<60 years) without clinical or echocardiographic evidence of cardiopulmonary disease, hypertension, or diabetes mellitus

  • This term is now considered potentially confusing and should not be used to guide therapeutic decisions 1

• Non-valvular AF: AF occurring in the absence of rheumatic mitral valve disease or prosthetic heart valve 1

Newer Staging Classification

The 2023 ACC/AHA/ACCP/HRS guidelines introduced a new staging system viewing AF as a disease continuum 2, 3:

1. Stage 1 (At Risk): Patients with AF-associated risk factors (e.g., obesity, hypertension)
2. Stage 2 (Pre-AF): Signs of atrial pathology on ECG or imaging without documented AF
3. Stage 3: Presence of paroxysmal or persistent AF
4. Stage 4: Permanent AF

Associated Arrhythmias

AF may occur in association with other atrial arrhythmias:

• Atrial Flutter: More organized than AF, characterized by a saw-tooth pattern of regular atrial activation (flutter waves) on ECG

  • Typical atrial flutter involves a macroreentrant circuit through the cavotricuspid isthmus
  • May alternate with AF or transform into AF 1

• Atrial Tachycardia: Characterized by regular, organized atrial activity with discrete P waves and an isoelectric segment between P waves

  • Can trigger AF, especially when originating from pulmonary veins 1

Autonomic Influence on AF

Based on autonomic tone, AF can be classified as 2:

• Vagally-mediated AF: More common form

  • Typically occurs at night or after meals
  • Greater prevalence in men
  • Onset around age 40-50
  • Often associated with lone AF

• Adrenergically-induced AF: Less common

  • Occurs during daytime in patients with organic heart disease
  • Provoked by exercise or emotional stress
  • Polyuria is a common correlate

Understanding these subtypes is crucial for appropriate management strategies, as treatment approaches may differ based on AF classification, patient symptoms, and associated comorbidities.