Paroxysmal Atrial Fibrillation: Definition and Clinical Characteristics
Paroxysmal atrial fibrillation (PAF) is recurrent atrial fibrillation that terminates spontaneously within 7 days, with most episodes lasting less than 24 hours. 1
Core Definition
Paroxysmal AF represents a specific temporal pattern of atrial fibrillation characterized by:
- Self-terminating episodes that resolve without medical intervention (cardioversion or antiarrhythmic drugs) 1
- Duration of 7 days or less, with the majority of episodes lasting under 24 hours 1
- Recurrent nature - by definition, the patient must have experienced 2 or more episodes to be classified as having paroxysmal AF rather than first-detected AF 1
- Episodes lasting at least 30 seconds are required for clinical diagnosis 1
Electrocardiographic Features
On ECG, paroxysmal AF demonstrates the same characteristics as other forms of atrial fibrillation:
- Absence of distinct P waves, replaced by rapid oscillations or fibrillatory waves that vary in amplitude, shape, and timing 1
- Irregularly irregular ventricular response when AV conduction is intact 1
- Rapid ventricular rate (typically when untreated) unless AV nodal blocking agents are present 1
Clinical Context and Progression
Paroxysmal AF is not a static diagnosis - the pattern can evolve over time:
- Episodes may progress from paroxysmal to persistent AF (lasting >7 days) or eventually to permanent AF 1
- Individual patients may experience both paroxysmal and persistent episodes, though classification is typically based on the most frequent presentation 1
- A patient with paroxysmal AF may have episodes lasting seconds to hours that recur repeatedly over years 1
Distinction from Other AF Patterns
The temporal classification system distinguishes paroxysmal AF from:
- Persistent AF: Episodes lasting more than 7 days that do not self-terminate 1
- Permanent AF: Continuous AF where rhythm control has been abandoned after shared decision-making between patient and physician 1
- First-detected AF: The initial episode, regardless of duration or symptoms, before the pattern is established 1
Important Clinical Caveats
Secondary AF should be classified separately - episodes occurring in the setting of acute myocardial infarction, cardiac surgery, pericarditis, myocarditis, hyperthyroidism, pulmonary embolism, or acute pulmonary disease are not considered paroxysmal AF, as treatment of the underlying condition typically eliminates the arrhythmia 1
The self-terminating nature is the critical distinguishing feature - if pharmacological therapy or electrical cardioversion is required to terminate the episode, it does not change the classification from persistent to paroxysmal 1
Epidemiological Significance
- Paroxysmal AF represents a substantial proportion of all AF cases, with estimates suggesting over 40% of AF patients have the paroxysmal form 2
- An estimated 2.2-2.3 million people in North America have paroxysmal or persistent AF 1
- The condition is progressive, with paroxysmal AF often evolving toward more sustained forms through atrial remodeling 3, 4