Introduction to Pacemaker Rhythms

Overview

pacemaker illustration

This page provides an introduction to pacemaker rhythms with links to our free lessons and drills.

Pacemakers provide an artificial electrical impulse to the heart. This impulse and the hearts natural electrical signals can be interpreted. We provide a training module for pacemaker rhythms and links to practice strips of pacemaker patients.

There are multiple types of pacemaker rhythms:

  • Normal Single Chamber Pacemaker
  • Normal Dual Chamber Pacemaker
  • Failure to Capture
  • Failure to Pace
  • Failure to Sense


Pacemaker Rhythm Sample Tracing

pacemaker rhythm EKG tracing

Categories of Pacemaker Rhythms

Normal Single Chamber Pacemaker

Normal Single Chamber Pacemaker EKG tracing

Failure to Capture

Failure to Capture EKG tracing Failure to capture means that the ventricles fail to response to the pacemaker impulse. On an EKG tracing, the pacemaker spike will appear but it will not be followed by a QRS complex.

Failure to Pace

Failure to Pace EKG tracing Failure to pace occurs when the pacemaker does not generate an electrical impulse. On an EKG tracing, pacemaker spikes will be missing.

Failure to Sense

Failure to sense occurs when the pacemaker does not detect the patient's myocardial depolarization. This can often be seen on an EKG tracing as a spike following a QRS complex too early.
Click To Begin Pacemaker Rhythms Training Module

Overview

Pacemaker Rhythms

Thomas E. O'Brien
AS CCT CRAT RMA

Learning Objectives

At the conclusion of this training module the reader will be able to:

  • Recall and apply the 5-steps of heart rhythm interpretation
  • Recognize the difference between regular and irregular rhythms
  • Recall the normal range for PR interval and QRS complex
  • Recognize the features and qualifying criteria for the following complexes and rhythms:
    • Atrial Pacemaker Rhythm
    • Ventricular Pacemaker Rhythm
    • Atrioventricular Pacemaker Rhythm
    • Failure (Loss) to Capture

Using This Presentation

how to use this presentation image

Pacemaker Rhythms

Introduction Part 1

  • Rhythms are often named according to the source of the electrical activity in the heart or the structure where the problem is occurring.
  • Pacemaker Rhythms are aptly named due to the locus of stimulation coming from an artificial impulse generator called a pacemaker.
  • The most common pacemakers may deliver an electrical impulse to the right atrium, right ventricle or both.
  • Artificial pacemakers are often implanted as a result of either a failure of the higher (faster) pacemakers within the heart or an irregular rhythm resulting in decreased cardiac output.
  • Remember, the fastest electricity in the heart (regardless of location or source) will dictate the heart rate.

Introduction Part 2

  • Each rhythm in this category will share unique a morphologic feature which separate them from all other rhythms.
  • Pacemaker rhythms are identified by the presence of a conspicuous vertical mark known as a “spike”.
  • If the spike precedes the P wave, it is referred to as an Atrial Pacemaker rhythm.
  • If the spike precedes the ventricular depolarization, it is referred to as a Ventricular Pacemaker rhythm.
  • If there is a spike prior to the P wave and the ventricular depolarization, it is referred to as an AV (atrioventricular sequential) Pacemaker rhythm. Note: QRS complexes in Ventricular and Atrioventricular Pacemaker rhythms will have a wide, bizarre appearance (just like ventricular rhythms) and typically measure 0.12 seconds or greater.
  • After learning the unique features just described, it is simply a matter of recalling the unique feature and associating it with the corresponding waveform.

Introduction Part 3

  • During implantation, pacemakers are programmed by the physician to provide electrical impulses at a specific strength of impulse (enough to cause depolarization) and with a certain rate to maintain cardiac output within a specific normal range.
  • Many pacemakers also are programmed to “sense” the inherent electrical activity occurring within the heart so the device only turns on when needed and does not compete with the patients own natural electrical activity.
  • Sensing capability is an important safety feature in pacemakers to ensure the electrical impulse provided by the pacemaker does not inadvertently occur during the vulnerable period of repolarization (relative refractory period).

Introduction Part 4

  • Unfortunately not all pacemakers work the way they should. According to Pub Med, an article titled “Complications related to permanent pacemaker therapy” (http://www.ncbi.nlm.nih.gov/pubmed/10353129): In a group of patients studied at Kuopio University Hospital, inadequate capture or sensing was observed in 7.4% of the patients.
  • A variety of problems can occur when is comes to pacemakers. The wire may not embed in the endocardium or pull out post-procedure, the device may oversense or undersense or fail to capture.

Terminology

Part 1

  • Oversensing occurs when the device interprets non-cardiac sources of energy as being cardiac. This results in the device not turning on when it should.
  • Undersensing results in a device that doesn’t know when to turn off. This may result in pacemaker competition, a potentially dangerous situation (as discussed earlier).
  • Capture refers to when the device delivers an electrical impulse of sufficient strength to result in depolarization. The waveform immediately follows the pacing spike.
  • Loss or Failure to Capture may occur for a number of reasons, but commonly occurs when the generator is unable to deliver a sufficient amount of energy to cause depolarization. This may be due to the age of the batteries. This will result in a spike with no corresponding depolarization or a delayed depolarization of unusual morphology.

Part 2

Capture – notice the waveform immediately following the pacing spike.

pacemaker ecg image 102

Loss of Capture – notice the 4th and 7th complex morphology is different and the waveform does not immediately follow the pacing spike.

pacemaker ecg image 102b

Atrial Pacemaker Rhythm

Description

  • This rhythm is easily identified by the conspicuous presence of a pacing spike immediately preceding the P wave.
  • Not all pacing spikes will look exactly the same. They may be below or above the isoelectric line or be partially above and below.
  • The PR interval is measured from the pacing spike to the beginning of ventricular depolarization.
pacemaker ecg image 103

Practice Strip

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

pacemaker ecg image 104

Answers

  • Rhythm: Regular
  • Rate: 83
  • P Wave: upright and uniform with spikes
  • PR interval: 0.16 sec
  • QRS: 0.06 sec
  • Interpretation: Atrial Pacemaker Rhythm with 100% capture
pacemaker ecg image 104b

Ventricular Pacemaker Rhythm

Ventricular Pacemaker Rhythm

  • This rhythm is easily identified by the conspicuous presence of a pacing spike immediately preceding the QRS complexes.
  • Sometimes there will be P waves in the tracing, sometimes there will not.
  • Follow the five-steps of rhythm analysis and document as always.
image P118 ventricular pace

Practice Strip

  • Analyze this tracing using the five steps of rhythm analysis
  • Compare your answers with the answers on the next slide
pacemaker ecg image ventricular

Practice Strip Answers

  • Rhythm: regular
  • Rate 83
  • P Wave: absent
  • The PR interval: n/a
  • QRS: 0.16 sec, wide and bizarre with spikes
  • Interpretation: Ventricular Pacemaker Rhythm with 100% capture

Atrioventricular Pacemaker Rhythm

Atrioventricular Rhythm

  • This rhythm is easily identified by the conspicuous presence of a pacing spike immediately preceding the P waves and the QRS complexes.
  • The PR interval is measured from the atrial spike to the ventricular spike. This is also referred to as AV delay.
  • This “delay” is programmed by the physician during implantation to mimic the natural delay of the PR interval to facilitate the “atrial kick”.
atrioventricular tracing

Practice Strip

  • Analyze this tracing using the five steps of rhythm analysis.
  • Compare your answers with the answers on the next slide.
atrioventricular tracing question

Practice Strip Answers

  • Rhythm: regular
  • Rate 88
  • P Wave: upright and uniform with spikes
  • PR interval: 0.18 sec
  • QRS: 0.16 sec, wide and bizarre with spikes
  • Interpretation: Atrioventricular (sequential) Pacemaker Rhythm

Failure (Loss) to Capture

Description

  • When a pacemaker loses its ability to cause depolarization (capture), the inherent rhythm of the patient will become present within the tracing.
  • As mentioned earlier in this presentation you will note the presence of a pacing spike, but you will not see a waveform immediately following it.
  • You will likely see a delay after the spike, then the presence of some waveform of different morphology
pacemaker ecg image 109

Practice Strip

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

pacemaker ecg image 110

Answers

  • Rhythm: Irregular
  • Rate: 80
  • P Wave: absent
  • PR interval: n/a
  • QRS: 0.14 sec, two non-captured complexes 0.16 sec, all wide and bizarre
  • Interpretation: Ventricular Pacemaker Rhythm with Loss of Capture
pacemaker ecg image 110b

Test Questions 1-4

Question #1

When analyzing a rhythm strip, it qualifies as being regular when

A. the QT intervals are the same
B. the PR interval measures the same
C. the QRS complexes measures the same
D. the R - R intervals measure the same




Question #2

Which of the following steps is not one of the five-steps of rhythm analysis?

A. PR interval measurement
B. Rhythm regularity
C. TP interval measurement
D. QRS complex measurement




Question #3

Which of the following is considered normal range of the QRS complex?

A. 0.12 - 0.20 minutes
B. 0.06 - 0.10 minutes
C. 0.12 - 0.20 seconds
D. 0.06 - 0.10 seconds




Question #4

Which of the following is considered normal range of the PR interval?

A. 0.12 - 0.20 minutes
B. 0.06 - 0.10 minutes
C. 0.12 - 0.20 seconds
D. 0.06 - 0.10 seconds





Test Questions 5-9

Question #5

Which feature is most closely associated with all pacemaker rhythms?

A. Wide & bizarre QRS complexes
B. PR interval measuring greater than 0.20 seconds
C. Pacing spikes
D. Inverted P waves




Question #6

Undersensing refers to which of the following?

A. the generator is unable to deliver a sufficient amount of energy to cause depolarization.
B. the device delivers an electrical impulse of sufficient strength to result in depolarization.
C. the device interprets non-cardiac sources of energy as being cardiac. This results in the device not turning on when it should.
D. a device that doesn’t know when to turn off.




Question #7

Loss of Capture refers to which of the following?

A. the generator is unable to deliver a sufficient amount of energy to cause depolarization.
B. the device delivers an electrical impulse of sufficient strength to result in depolarization.
C. the device interprets non-cardiac sources of energy as being cardiac. This results in the device not turning on when it should.
D. a device that doesn’t know when to turn off.




Question #8

Oversensing refers to which of the following?

A. the generator is unable to deliver a sufficient amount of energy to cause depolarization.
B. the device delivers an electrical impulse of sufficient strength to result in depolarization
C. the device interprets non-cardiac sources of energy as being cardiac. This results in the device not turning on when it should.
D. a device that doesn’t know when to turn off.




Question #9

Capture refers to which of the following?

A. the generator is unable to deliver a sufficient amount of energy to cause depolarization
B. the device delivers an electrical impulse of sufficient strength to result in depolarization
C. the device interprets non-cardiac sources of energy as being cardiac. This results in the device not turning on when it should.
D. a device that doesn’t know when to turn off





Test Questions 10-12

Question #10

heart block quiz tracing 1

Select the heart rate most closely associated with this tracing.

A. 143
B. 100
C. 88
D. 62




Question #11

heart block quiz tracing 2

What is the most correct interpretation of this tracing?

A. Atrial Pacemaker Rhythm
B. Normal Sinus Rhythm
C. Ventricular Pacemaker Rhythm
D. Atrioventricular Pacemaker Rhythm




Question #12

heart block quiz tracing 2

What is the PR interval measurement in this tracing?

A. 0.04 sec
B. 0.10 sec
C. 0.18 sec
D. 0.24 sec





Test Questions 13-15

Question #13

What would be the most proper description of the atrial morphology in this tracing?

ekg ventricular quiz tracing 12
A. Upright with spikes
B. Absent
C. Inverted
D. Biphasic




Question #14

What is the most correct interpretation of this tracing?

ekg ventricular quiz tracing 12
A. Atrial Pacemaker Rhythm
B. Normal Sinus Rhythm
C. Ventricular Pacemaker Rhythm
D. Atrioventricular Pacemaker Rhythm




Question #15

Which term is most appropriately used to describe the QRS morphology in this tracing?

ekg ventricular quiz tracing 12
A. Normal
B. Wide and bizarre
C. Variable
D. All answers are incorrect





Test Questions 16-18

Question #16

. What would be the most proper description of the pacemaker activity in this tracing?

ekg ventricular quiz tracing 15
A. 100% Capture
B. Constant
C. Absent
D. Loss of Capture




Question #17

Select the number that most closely represents the heart rate.

ekg ventricular quiz tracing 15
A. 80
B. 65
C. 45
D. 30




Question #18

What is the most correct interpretation of this tracing.

ekg ventricular quiz tracing 15
A. Atrial Pacemaker Rhythm
B. Ventricular Pacemaker with Loss of Capture
C. Ventricular Pacemaker Rhythm
D. Atrioventricular Pacemaker Rhythm





Test Questions 19-20

Question #19

What is the most correct interpretation of this tracing?

ekg pacemaker quiz tracing 19
A. Atrial Pacemaker Rhythm
B. Normal Sinus Rhythm
C. Ventricular Pacemaker Rhythm
D. Atrioventricular Pacemaker Rhythm




Question #20

What tracing feature are the two red arrows pointing at in the corresponding image?

ekg pacemaker quiz tracing 19
A. Artifact
B. Calibration markings
C. Pulse boxes
D. Pacing spikes





EKG Self Test

EKG Rhythms Self Test

If you would like to tests the knowledge and skills learned in this module, use our EKG Rhythms Self Test. You can choose to focus this self-test on any of all of the following:

  • Sinus Mechanisms
  • Atrial Rhythms
  • Junctional Rhythms
  • Ventricular Rhythms
  • Atrioventricular Blocks
  • Pacemaker Rhythms

EKG Rhythm Tests »

Free Training Resources

Pacemaker Rhythms Training

As a starting point for mastering pacemaker rhythms, we recommend our free pacemaker rhythms module This module focuses on the features and qualifying criteria of pacemaker rhythms and failures.

Pacemaker Rhythms

EKG Rhythm Tests

Hundreds heart rhythms in this practice test. Test can be tailored for specific learning needs.

EKG Rhythm Tests


External References

Wikipedia
Free Dictionary