Rhythm Analysis Method - Course # 313-2
The five steps of rhythm analysis will be followed when analyzing any rhythm strip. Analyze each step in the following order.
- Rhythm Regularity
- Heart Rate
- P wave morphology
- P R interval or PRi
- QRS complex duration and morphology
- Carefully measure from the tip of one R wave to the next, from the beginning to the end of the tracing.
- A rhythm is considered “regular or constant” when the distance apart is either the same or varies by 1 ½ small boxes or less from one R wave to the next R wave.
Heart Rate Regular (Constant) Rhythms
- The heart rate determination technique used will be the 1500 technique.
- Starting at the beginning of the tracing through the end, measure from one R wave to the next R wave (ventricular assessment), then P wave to P wave (atrial assessment), then count the number of small boxes between each and divide that number into 1500. This technique will give you the most accurate heart rate when analyzing regular heart rhythms. You may include ½ of a small box i.e. 1500/37.5 = 40 bpm (don’t forget to round up or down if a portion of a beat is included in the answer).
Step 2 (Cont.)
Heart Rate - Irregular Rhythms
- If the rhythm varies by two small boxes or more, the rhythm is considered “irregular”.
- The heart rate determination technique used for irregular rhythms will be the “six-second technique”.
- Simply count the number of cardiac complexes in six seconds and multiply by ten.
P wave Morphology (shape)
- The lead most commonly referenced in cardiac monitoring is lead II.
- In this training module, lead two will specifically referenced unless otherwise specified.
- The P wave in lead II in a normal heart is typically rounded and upright in appearance.
- Changes in shape must be reported. This can be an indicator that the locus of stimulation is changing or the pathway taken is changing.
- P waves may come in a variety of morphologies i.e. rounded and upright, peaked, flattened, notched, biphasic(pictured), inverted and even buried or absent!
- Remember to describe the shape. This can be very important to the physician when diagnosing the patient.
PR interval (PRi)
Constant PR Interval
Variable PR Interval
- Measurement of the PR interval reflects the amount of time from the beginning of atrial depolarization to the beginning of ventricular depolarization.
- Plainly stated, this measurement is from the beginning of the P wave to the beginning of the QRS complex.
- The normal range for PR interval is: 0.12 – 0.20 seconds (3 to 5 small boxes)
- It is important that you measure each PR interval on the rhythm strip.
- Some tracings do not have the same PRi measurement from one cardiac complex to the next. Sometimes there is a prolonging pattern, sometimes not.
- If the PR intervals are variable, report them as variable, but note if a pattern is present or not.
- QRS represents ventricular depolarization.
- It is very important to analyze each QRS complex on the tracing and report the duration measurement and describe the shape (including any changes in shape).
- As discussed in step 3, when referring to P waves, remember changes in the shape of the waveform can indicate the locus of stimulation has changed or a different conduction pathway was followed. It is no different when analyzing the QRS complex. The difference is that in step 3, we were looking at atrial activity. Now we are looking at ventricular activity.
- Measure from the beginning to the end of ventricular depolarization.
- The normal duration of the QRS complex is: 0.06 – 0.10 second
How to use this module.
This module is organized into a series of lessons. These lessons are listed on the right side of the content area. To navigate to a lesson, either
click on the lesson name or use the arrows at the bottom right. Each lesson contains several slides. These slides are lists with tabs
that appear above each slide. To navigate to a slide, either click on the tab or use the gray arrows that appear on the left and right sides of the slides.
Within the lesson are questions. These questions are used to reinforce key concepts, but they are not used for scoring or grading. After
completing this module, we encourage you to use our drills and quizzes to practice what you have learned. Finally, after completing most or all of
the modules, you might try our EKG Graded Quizzes to test your knowledge.
Our affiliated website, Practical Clinical Skills, provides additional drills and quizzes with certifcates of achievement. If you have an account, then your signin name and password will
work on that website as well. Click here for EKG contents and apps at Practical Clinical Skills.
313 Rhythm Analysis Method - Course # 313-2