Assessing Cardiac Rhythm | ECG Basics - MedSchool
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ECG Basics
 
 
ECG Basics
When assessing rhythm on an ECG, look at both the regularity of P waves (sinoatrial rhythm) and R waves (ventricular rhythm).ECG Rhythm is best assessed using the rhythm strip, which is usually lead II.
 

Assessing Cardiac Rhythm

 
 

Overview

  • When assessing rhythm on an ECG, look at both the regularity of P waves (sinoatrial rhythm) and R waves (ventricular rhythm).
  • ECG Rhythm is best assessed using the rhythm strip, which is usually lead II.

Sinoatrial Rhythm

  • Sinoatrial rhythm can be assessed by examining the P waves on the rhythm strip.
  • Check whether each QRS complex is preceded by a P wave, as well as the regularity of the interval between P waves (PP interval).
    • Causes of Irregular Atrial Rhythm

    • Sinus Node

    • Sinus arrhythmia
    • Sinus pause
    • Second degree sinoatrial exit block
    • Atrium

    • Premature atrial complexes
    • Multifocal atria tachycardia
    • Examples

    • Second degree sinoatrial block, Mobitz type I - note progressively shortened PP intervals, followed by a pause:
    • Second degree sinoatrial block, Mobitz type I - note progressively shortened PP intervals, followed by a pause
       
    • Multifocal atrial tachycardia - a variety of P wave morphologies with variable PP intervals indicates several atrial foci:
    • Multifocal atrial tachycardia - a variety of P wave morphologies with variable PP intervals indicates several atrial foci
       

Ventricular Rhythm

  • Ventricular rhythm can be assessed by examining the QRS complexes on the rhythm strip.
  • Measure the interval between R waves (RR interval) and whether this interval is regular or irregular across the rhythm strip. This can be assessed by marking the R waves on a separate piece of paper, and then transposing the paper to another part of the rhythm strip to see if the R waves line up.
    • Interpretation

    • Regular rhythm - constant RR interval
    • Regularly irregular rhythm - variable RR interval with a predictable pattern
    • Irregularly irregular rhythm - variable RR interval with a random pattern
    • Causes of Irregular Ventricular Rhythm

    • Tachycardia

    • Multifocal atrial tachycardia
    • Atrial fibrillation
    • Atrial flutter with variable block
    • Polymorphic ventricular tachycardia
    • Bradycardia

    • Sinus arrhythmia
    • Sinus arrest
    • Second or third degree sinoatrial exit block
    • Atrial fibrillation with slow ventricular rate
    • Atrial flutter with variable block
    • Second or third degree AV block
    • Examples

    • Atrial fibrillation - note a baseline fibrillation wave with irregular ventricular rhythm:
    • Atrial fibrillation - note a baseline fibrillation wave with irregular ventricular rhythm
       
    • Third degree (complete) AV block - bradycardia with complete dissociation between P waves and QRS complexes is characteristic:
    • Third degree (complete) AV block - bradycardia with complete dissociation between P waves and QRS complexes is characteristic
       
Last updated on September 20th, 2018
 
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