Atrial Rhythms | Premature Atrial Complex

Thomas E. O'Brien
AS CCT CRAT RMA

Learning Objectives

After completing this atrial rhythms module and its quiz, you will be able to:

  • Apply the 5-steps of heart rhythm interpretation
  • Recognize regular vs irregular rhythms
  • Remember the normal time interval range for PR interval and QRS complex
  • Recognize key features and criteria for these atrial rhythms:
    • Premature Atrial Complexes
    • Wandering Atrial Pacemaker Rhythm
    • Multifocal Atrial Tachycardia
    • Atrial Flutter
    • Atrial Fibrillation

Course Progress Tracking

A quiz is available upon completion of this module.

Certificates of achievement are also available to registered users.


Authors and Reviewers

Authored by Thomas O'Brien.
Medically reviewed by Dr. Jonathan Keroes, MD, Cardiology.
Last Update: 2/4/2022





Rhythm Analysis Method

This module assumes that you have a good understanding of the 5-step EKG rhythm analysis method. Use the button below if you would like to read our lesson on 5-step rhythm analysis.

5-step Rhythm Analysis Lesson


Interpretation

Introduction

  • The five-steps of rhythm analysis must be followed regardless of how simple of complex the tracing is you are reviewing.
  • The information gathered in these steps are telling a story.
  • The title of that story is the interpretation.

Atrial Dysrhythmias Types

The dysrhythmias in this category occur as a result of problems in the atria. These atrial dysrhythmias primarily affect the P wave. We will be discussing the following complexes and rhythms:

  • Premature Atrial Complexes (PAC’s)
  • Wandering Atrial Pacemaker
  • Multifocal Atrial Tachycardia
  • Atrial Flutter
  • Atrial Fibrillation

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Premature Atrial Complex (PAC)

Intro to PAC

  • PAC's can occur for a number of different reasons i.e., diet, fatigue, stress, disease, ischemia to name a few.
  • Premature complexes frequently occur in bradycardic rhythms, but may occur almost any time.
  • PAC's occur when an early electrical impulse occurs from a location in the atria other than the SA node.

Intro to PAC 2

  • This early impulse causes an early cardiac complex which disrupts the underlying rhythm.
  • The locus of stimulation being different, results in a change in the morphology of the P wave.
  • PAC's can occur occasionally or frequently.
  • PAC's can be observed with or without a pattern
  • The P wave with PAC's will always be upright

EKG Analysis

atrial ecg image

Notice the following: the R to R interval is irregular, the fifth complex is early and the P wave on the early complex is a different shape.

EKG Practice Strip

atrial ecg image 2

Analyze this tracing using the five steps of rhythm analysis.

Show Answer
  • Rhythm: Irregular
  • Rate: 50
  • P wave: Upright & uniform (except early complexes - biphasic)
  • PR interval: 0.16 second
  • QRS: 0.08
  • Interpretation: Sinus Bradycardia with PAC's


Wandering Atrial Pacemaker

Description

  • Rhythms are often named according to the origin of the electrical activity in the heart or the structure where the problem is occurring.
  • Wandering Atrial Pacemaker is aptly named due to the electrical impulses causing the atrial activity are moving or wandering.
  • These changes in the locus of stimulation affect the morphology of the P waves.

Analysis

wandering atrial pacemaker tracing
  • In Wandering Atrial Pacemaker, you must observe at least three different shaped P waves. No other changes in the tracing may be observed. The rhythm may or may not be regular.
  • The PR interval is often affected, but does not have to be.
  • The bottom line, is you must observe at least three different shaped P waves.

Practice Strip

wandering atrial pacemaker tracing

Analyze this tracing using the five steps of rhythm analysis.

Show Answer
  • Rhythm: Irregular
  • Rate: 50
  • P wave: Changing Shapes (3 or more)
  • PR interval: Variable
  • QRS: 0.08
  • Interpretation: Wandering Atrial Pacemaker

Multifocal Atrial Tachycardia

Multifocal Atrial Tachycardia

  • Multifocal Atrial Tachycardia is just a faster version of Wandering Atrial Pacemaker. The criteria is the same as Wandering Atrial Pacemaker with the only difference being the heart rate exceeds 100 bpm.
  • These changes in the locus of stimulation within the atria affect the morphology of the P waves.
  • Remember, you must observe at least three different shaped P waves.
  • Due to the presence of irregular R to R intervals coupled with the changing P wave morphology, some people have confused this rhythm with Atrial Fibrillation.

Atrial Flutter

Description

  • Atrial Flutter occurs when there is an obstruction within the atrial electrical conduction system.
  • Due to this impediment a series of rapid depolarizations occur.
  • These depolarizations may occur two, three, four or more times per QRS complex.
  • The AV node functions like a “gatekeeper” blocking the extra impulses until the ventricular conduction system is able to accept the impulse.
  • The impulse that is accepted will cause the QRS complex to occur.

Analysis

atrial flutter tracing
  • Each flutter wave represents atrial depolarization. This will be noted next to the P wave step in rhythm analysis. Instead of P waves, this tracing has “F” waves. No P waves mean there is no PR interval measurement.
  • When the tracing is interpreted, the ratio of F waves to each QRS complex will be documented along with the rhythm i.e. Atrial Flutter 4:1 (indicates 4 “F” waves to each QRS complex). Not all Atrial Flutter will have a regular rhythm. In that case just document and report your observations.

Practice Strip

atrial flutter ecg
  • Analyze this tracing using the five steps of rhythm analysis.
  • Compare your answers with the answers on the next slide.

Practice Strip Answers

atrial flutter ekg
  • Rhythm: Regular
  • Rate: Ventricles - 80, Atria - 320
  • P wave: "F" waves
  • PR interval: absent
  • QRS: 0.08
  • Interpretation: Atrial Flutter 4:1

Atrial Fibrillation

Description

  • Atrial Fibrillation occurs when multiple electrical impulses occur within the atria. This chaotic electrical activity results in a chaotic wave form between the QRS complexes. P waves are absent. They are replaced by lower case "f" waves. No P waves means there is no PR interval measurement.
  • This rapid electrical activity overwhelms the AV node causing impulses to enter the ventricular conduction system at irregular points. This results in irregular R to R intervals.

Analysis

  • Not all fibrillatory waves are created equal. The "f" waves can be coarse (majority measure 3 mm or more) or can be fine (majority of waveforms measure less than 3 mm) to almost absent. Regardless always report your observations. Many times when a patient has "new onset" Atrial Fibrillation the patient will report with a heart rate of 160 bpm or more.

Mechanisms

atrial fibrillation tracing
  • When a patient experiences A-fib, the atria are not contracting as they normally would. They are just quivering. This absence of contraction of the atria can result in a loss of cardiac output anywhere from 15 - 30% due to the absence of "atrial kick". This is why the heart rate is so high. The body is trying to maintain homeostasis.
  • It will be impossible to determine the atrial rate. You will only be able to analyze and report the ventricular rate.
  • Atrial Fibrillation with a ventricular response in excess of 100 bpm is commonly referred to as Atrial Fibrillation with “rapid ventricular response” or "uncontrolled A-fib".

Practice Strip

atrial fibrillation ecg

Analyze this tracing using the five steps of rhythm analysis.

Show Answer
  • Rhythm: Irregular
  • Rate: Ventricles - 90, Atria - Unable to determine (UTD)
  • P wave: "f" waves
  • PR interval: absent
  • QRS: 0.08
  • Interpretation: Atrial Fibrillation

Quiz

After you have completed the course materials, use the button below to take the course quiz. Scores of 70% and higher will be saved to your dashboard, provided that you are signed-in. And yes, you can retake the quiz without penalty. We keep your highest score.

Atrial Rhythms Course Quiz
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