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Test Findings
 
 

Absence of P Waves

 
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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.
AtriaVentricles
Atrial FibrillationIrregular
350 - 600 bpm
Irregular
100 - 180 bpm
Atrial FlutterRegular
~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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