Editor’s note: The EKG Detective will be a monthly column dedicated to illustrating the benefits of utilizing deductive logic as a method for interpreting ECG tracings. The column will highlight and review all the basic ECG interpretations, before transitioning into a monthly interpretation challenge. See you next month and remember, it is always better to practice as a clinician rather than a technician.
Welcome back to the EKG Detective. This column is dedicated to illustrating the benefits of utilizing deductive logic as a method for interpreting EKG tracings. For this month’s article, we will be looking at atrial fibrillation.
If you need a refresher on inductive and deductive logic, check out our introductory article.
Fill out the form on this page to download your copy of the EKG Detective Interpretation Checklist.
Throughout this series, we will be using the EKG Detective Interpretation Checklist (see Figure 1). This checklist is intended to prompt providers through five sequential elements associated with basic EKG interpretation while working through the specific criteria for each element:
- Rhythm regularity
- Rhythm rate
- P-wave criteria
- PR interval
- QRS criteria
EKG rhythms will be eliminated as we identify criteria within the EKG tracing until there is only one probable interpretation. We will use this checklist to illustrate how deduction is used to interpret an ECG tracing. More practically, it can be used as an EKG interpretation job aid.
Atrial fibrillation
For this article, we will be looking at atrial fibrillation. Atrial fibrillation occurs when multiple foci within the atria are firing simultaneously. As a byproduct, this results in chaotic electrical firing within the atria that is frequently depolarizing at rates above 350 beats per minute.
EKG Category 1: Rhythm regularity
Atrial fibrillation is characterized by an irregular rhythm. The irregularity is due to the AV junction being overwhelmed by all the chaotic electrical activity coming from within the atria. This electrical chaos prevents the AV junction from being able to consistently space as well as process all the overwhelming number of electrical impulses coming from the atria. As atrial fibrillation is irregular, we can eliminate any rhythm that is irregular (see Figure 3).
In some instances, there may appear to be pauses. For pauses to be present, there needs to be R-to-R regularity before and after the pause. This is not the case, and pauses will be absent with atrial fibrillation. As atrial fibrillation is irregular without pauses, we can eliminate sinus arrest and sinus exit block from the checklist (See Figure 4 for eliminated rhythms with pauses).
PAC/s or PJC/s cannot be identified in atrial fibrillation because P-waves are difficult to isolate due to the chaotic atrial activity. PVC/s are not present because there are no wide QRS complexes. As there are no ectopic beats within this rhythm, we can eliminate them from the checklist (see Figure 5 for all eliminated rhythms from regularity of rhythm).
EKG Category 2: Rhythm rate
Atrial fibrillation cannot be defined by its rate. The ventricular rate typically falls between 60-100 beats per minute, but it can also be less than 60 or greater than 100 beats per minute. Due to the variability of ventricular rates for atrial fibrillation, no rhythms will be eliminated from the checklist based upon this criterion.
EKG Category 3: P-wave criteria
Do the P-waves appear to be saw-toothed and/or flutter waves? Atrial fibrillation does not have flutter waves so we can eliminate atrial flutter off the checklist (see Figure 6).
Are the P-waves discernible? Due to chaotic electrical activity within the atria, similar, consistent and individually identifiable P-waves are non-existent. In atrial fibrillation, the ECG baseline typically presents with a jagged and/or wavery appearance. The term that describes this chaotic electrical activity is frequently described as “non-discernible P-waves” and/or a “fibrillatory baseline.” As P-waves are non-discernible, we can eliminate all the rhythms except for the atrial fibrillation off the checklist (see Figure 7).
EKG Category 4: PR interval
There is no need to move onto the EKG Category 4: “PR interval,” because the only remaining choice is the atrial fibrillation we have been working from.
EKG Category 5: QRS criteria
There is no need to move onto EKG Category 5: QRS Criteria, because the only remaining choice is the atrial fibrillation we have been working from.
Identifying atrial fibrillation
This example illustrates how deductive logic is used to interpret atrial fibrillation. Electrical impulses within the atria are chaotic and beat at greater than 350 beats per minute. This type of electrical activity makes it impossible to identify similar and consistent P-waves. Focus on identifying rhythm irregularity in conjunction with determining P-waves that are non-discernible. These are the two hallmark indicators that are key to identifying atrial fibrillation.
See you next month and remember, it is always better to practice as a clinician rather than a technician.
