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.
If you have been trained to interpret ECG rhythm strips, there is a good possibility you were taught to use inductive logic. Utilizing inductive logic is not bad, but it requires the practitioner to acquire more data than is typically necessary to interpret an ECG tracing.
On the other hand, deductive logic is easier because it focuses on what you can identify within an ECG tracing, rather than the criteria.
Inductive logic is based upon gathering evidence until you have acquired enough data to make an ECG interpretation. This method of logic is typically used to teach medical practitioners how to interpret ECG tracings. The challenge with utilizing inductive logic is you may not acquire the piece or pieces of evidence you need to interpret the ECG. It also requires the practitioner to memorize all the criteria for every ECG interpretation.
The premise behind deductive logic is reducing options based upon what you can identify within the ECG tracing. This helps the practitioner to focus on the ECG tracing rather than the criteria required to interpret the ECG. The greatest benefit of deductive logic is it frees the practitioner from having to memorize all the criteria required to interpret an ECG tracing.
The EKG Detective Interpretation Checklist (Figure 1) is intended to prompt providers through five sequential elements associated with basic ECG interpretation while working through the specific criteria for each element:
- Rhythm regularity
- Rhythm rate
- P-wave criteria
- PR interval
- QRS criteria
Fill out the form on this page to download your copy of the EKG Detective Interpretation Checklist.
ECG rhythms will be eliminated as we identify criteria within the ECG tracing until there is only one probable interpretation. We can use this checklist to illustrate how deduction is used to interpret an ECG tracing. More practically, it can be used as an ECG interpretation job aid.
Sinus rhythm
Use the EKG Detective Interpretation Checklist to interpret ECG tracings by utilizing deductive logic rather than the traditional inductive methods. For example, Figure 2 uses a sinus rhythm to illustrate the principle (See figure 2).
- ECG Category 1: “Rhythm regularity”
- As a sinus rhythm is regular, we should eliminate any rhythm that is irregular
- We can also eliminate ectopic beats, because they cause a rhythm to be irregular (Figure 3)
- ECG Category 2: “Rhythm rate”
- As a sinus rhythm is typically between 60-99 beats/minute, we should eliminate any rhythms that do not fall between these rates (Figure 4)
- ECG Category 3: “P-wave criteria”
Working through the “Specific Criteria” for P-waves:- Do the P-waves appear to be saw-toothed and/or flutter waves? As a sinus rhythm does not have flutter-waves, we should eliminate atrial flutter.
- Are the P-waves discernible? As P-waves are discernible in a sinus rhythm, we should eliminate accelerated idioventricular rhythm, because it has no P-waves.
- Are there three or more different-looking P-waves? As a sinus rhythm has just one P-wave morphology, we should eliminate wandering atrial pacemaker.
- Is there more than one P-wave for every QRS complex? As a sinus rhythm has one P-wave for every QRS, we should eliminate all the heart blocks, except for sinus rhythm with 10.
- Are the P-waves in front or after the QRS complex? P-waves in a sinus rhythm are in front of the QRS. Based upon identification of this criteria, none of the remaining rhythms should be eliminated. (See Figure 5 for all the eliminated rhythms from P-wave criteria)
- ECG Category 4: “PR interval”
- Since PR intervals for a sinus rhythm is typically between 0.12-0.20 seconds, we should eliminate sinus rhythm with 10 and junctional rhythm. (See figure 6)
There is no need to move onto ECG Category 5 “QRS Criteria,” because the only remaining choice is the sinus rhythm we have been working from.
Focus on the wave forms
Historically, inductive logic has been the common method used for interpreting basic ECG rhythms. Although inductive logic is not bad, it is by no means the simplest method. By making the transition to deductive logic, practitioners can focus on the wave forms required to interpret the ECG, rather than the criteria.
