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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