1. 6
Interpretation of an
EKG Strip

2. Anatomy of the Heart Objectives
Describe the basic approach to interpretation of EKG strips
Explain the five steps used in interpretation of EKG strips
Explain how to calculate heart rate, given a 6-second strip
Name four causes of artifact

3. General Rules First and most important, look at your patient
Read EVERY strip from left to right, starting at the beginning of the strip
Apply the five-step systematic approach that you will learn in this chapter
Avoid shortcuts and assumptions

4. General Rules
A quick glance at a strip will often lead to an incorrect interpretation
Ask and answer each question in the five-step approach in the order that is presented here… this is important for consistency
Master the accepted parameters for each dysrhythmia and apply them to each of the five steps when analyzing the strip

5. The Five-Step Approach
This five-step approach, in order of application, includes analysis of the following
Step 1: Heart rate
Step 2: Heart rhythm
Step 3: P wave
Step 4: PR interval
Step 5: QRS complex

6. Step 1: Heart Rate
Number of electrical impulses as represented by PQRST complexes conducted through the myocardium in 60 seconds (1 min)
Atrial rate
Counting the number of P waves noted
Ventricular rate
Counting the number of QRS complexes noted

7. Heart Rate
SA node discharges impulses at a rate of times per minute
Bradycardia
Heart rate less than 60 bpm
Tachycardia
Heart rate greater than 100

8. Heart Rate Determination
Two methods of determination of the heart rate
1. The 6-second method
Denotes a 6-second interval on EKG strip
Strip is marked by 3-or 6-second tick marks on the top or bottom of graph paper
Count the number of QRS complexes occurring within the 6-second interval and then multiply that number by 10

9. Sample of 6-Second Method

10. Two Methods to Determine Heart Rate
Two methods of determination of the heart rate
2. Second method is the R-R interval method
Most accurate if heart rate is regular
An estimation of the heart rate
Look at QRS complex that falls on a heavy line on the strip, count number of large boxes between this R wave and the next R wave
Divide this number into 300
Or use small boxes and divide by 1500

11. Sample Strip for R - R Method

12. STEP 2: Heart Rhythm Rhythm Classified as
Sequential beating of the heart as a result of the generation of electrical impulses
Classified as
Regular pattern
Interval between R waves are regular
Irregular pattern
Interval between R waves are not regular

13. Regular Rhythm
Measure the intervals between P to P waves or R to R waves
If the intervals vary by less than 0.06 seconds or 1.5 small boxes, we can consider the rhythm to be regular

14. Irregular Rhythm
If the intervals between the P to P waves or R to R waves are variable by greater than 0.06 seconds (1 ½ boxes), rhythm is considered irregular
Regularly irregular
Irregular rhythms that occur in a pattern
Occasionally irregular
Intervals of only one or two R to R are uneven

15. Irregular Rhythm
If the intervals between the P to P waves or R to R waves are variable by greater than 0.06 seconds, rhythm is considered irregular
Irregularly irregular
R to R intervals exhibit no similarity

16. Practice Strip for Rate and Rhythm Analysis
Pg 63 top

17. Practice Strip for Rate and Rhythm Analysis
Pg 63 bottom

18. STEP 3: The P Wave
P wave is produced when the right and left atria depolarize
First deviation from the isoelectric line
Should be rounded and upright
P wave is SA node pacing or firing at regular intervals
This pattern is referred
to as a sinus rhythm

19. P Wave: Five Questions to Ask
Step 1: Are P waves present?
Step 2: Are P waves occurring regularly?
Step 3: Is there one P wave present for each QRS complex present and/or is there a QRS for each P wave present?
Step 4: Are the P waves smooth, rounded,and upright in appearance, or are they inverted?
Step 5: Do all P waves look similar

20. P Wave Practice Strip

21. STEP 4: The PR Interval
Measures the time interval from the onset of atrial contraction to onset of ventricular contraction
Measured from onset of P wave to the onset of the QRS complex
Normal interval is
seconds
(3-5 small squares)

22. PR Interval: 3 Questions to Ask
1. Are PR intervals greater than 0.20 seconds?
2. Are PR intervals less than 0.12 seconds?
3. Are the PR intervals constant across the EKG strip?

23. PR Interval Practice Strip

24. STEP 5: The QRS Complex
Represents depolarization or contraction of the ventricles
Q wave
First negative or downward deflection of this large complex
R wave
First upward or positive deflection following the P wave (tallest waveform)
S wave
The sharp, negative, or downward deflection that follows the R wave

25. QRS Complex: 3 Questions to Ask
1. Are QRS intervals greater than 0.12 seconds (wide) or are they less than 0.12 secs (Narrow)?
2. Are the QRS complexes similar in appearance across the EKG strip?

26. Sample QRS Rhythm Strip

27. The ST Segment
Begins with the end of the QRS complex and ends with the onset of the T wave (consistent with isoelectric line)
J-point
Point at which the QRS complex
meets the ST segment
If ST segment is elevated
or depressed, myocardial
ischemia or injury may be indicated

28. The T Wave Produced by ventricular repolarization or relaxation
Commonly seen as the first upward or positive deflection following the QRS complex

29. The U Wave Usually not visible on EKG strips
Cause or origin not completely understood
Typically follows the T wave
Appears much smaller than T wave, rounded, upright, or positive deflection if they are present

30. Artifact EKG waveforms from sources outside the heart
Interference seen on a monitor or EKG strip
4 causes
Patient movement
Loose or defective electrodes (fuzzy baseline)
Clean your pt……
Improper grounding (60 cycle interference)
Faulty EKG apparatus

31. Sample Rhythm Strip of Artifact