Absence of P Waves
April 1st, 2023
Overview
A lack of visible P waves preceding QRS complexes suggests a lack of sinus beats; this may occur with sinus dysfunction or in the presence of fibrillation or flutter waves. The P wave may also be hidden within the QRS complex.
| Atria | Ventricles | |
| Atrial Fibrillation | Irregular 350 - 600 bpm | Irregular 100 - 180 bpm |
| Atrial Flutter | Regular ~300bpm | Regular ~150bpm |
Causes of Absence of P Waves
- Lack of sinus beats - sinus arrest, sinoatrial axit block
- P wave hidden in the QRS complex - AV nodal reentrant tachycardia, AV reentrant tachycardia
- Fibrillation or flutter waves - atrial fibrillation, atrial flutter
Interpretation
Bradycardia
- Sinus arrest - complete lack of P waves
- Second degree sinoatrial exit block - intermittently missed PQRS complexes
- Complete sinoatrial block - indistinguishable from sinus arrest
- Junctional escape - bradycardia with QRS complexes and no P waves
Tachycardia
- Junctional tachycardia (AVNRT or AVRT) - regular narrow complex tachycardia with no visible P waves
- Atrial flutter - regular narrow complex tachycardia with regular saw-toothed baseline flutter waves
- Atrial fibrillation - irregularly irregular narrow complex tachycardia with an irregularly oscillating baseline and no discernable P waves
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