Atrial Fibrillation Rhythm Characteristics
No, atrial fibrillation is characterized by an irregularly irregular rhythm, not a regularly irregular rhythm. 1
ECG Characteristics of Atrial Fibrillation
Atrial fibrillation has specific diagnostic features on electrocardiogram:
- Absence of P waves: Consistent P waves are replaced by rapid oscillations or fibrillatory waves
- Fibrillatory waves: These vary in amplitude, shape, and timing
- Irregularly irregular ventricular response: The R-R intervals are completely irregular when AV conduction is intact 1
- Diagnostic criteria: Absolutely irregular RR intervals, absence of distinct P waves, and atrial cycle length usually <200 ms (≥300 bpm) when visible 2
Distinguishing Atrial Fibrillation from Other Arrhythmias
Atrial Flutter vs. Atrial Fibrillation
- Atrial flutter: Characterized by a saw-tooth pattern of regular atrial activation (flutter waves), particularly visible in leads II, III, aVF, and V1 1
- Atrial flutter ventricular response: Often presents with 2:1 AV block, resulting in a regular ventricular rate (typically around 150 beats per minute) 1
- Potential misdiagnosis: When atrial activity is prominent on ECG in more than one lead, AF may be misdiagnosed as atrial flutter 1
Other Regular Rhythms in AF Context
Regular cardiac cycles (R-R intervals) during apparent AF should raise suspicion for:
- AV block
- Ventricular tachycardia
- AV junctional tachycardia 1
Clinical Implications of Irregular Rhythm
The irregularly irregular rhythm of AF has important clinical implications:
- Diagnostic value: The irregular rhythm is a key diagnostic feature that helps distinguish AF from other supraventricular arrhythmias
- Hemodynamic effects: The irregular ventricular response can lead to decreased cardiac output
- Symptom correlation: Patients often perceive the irregularity as palpitations or "skipped beats"
- Treatment monitoring: Regularization of the rhythm may indicate conversion to sinus rhythm or development of another arrhythmia
Common Pitfalls in AF Rhythm Assessment
- Pacemaker presence: In patients with implanted pacemakers, diagnosis of AF may require temporary inhibition of the pacemaker to expose atrial fibrillatory activity 1
- Wide-complex tachycardia: A rapid, irregular, sustained, wide-QRS-complex tachycardia may represent AF with conduction over an accessory pathway or AF with underlying bundle-branch block 1
- Extremely rapid rates: Ventricular rates over 200 beats per minute suggest the presence of an accessory pathway or ventricular tachycardia 1
- Fluctuating patterns: The ECG pattern may fluctuate between atrial flutter and AF, reflecting changing activation of the atria 1
The irregularly irregular rhythm is a hallmark feature of atrial fibrillation that distinguishes it from other arrhythmias and has important diagnostic and treatment implications.