1. 6
Interpretation of an EKG Strip

2. Interpretation of an EKG Strip
Objectives
Recall the general rules to use when correctly identifying heart rhythms
Describe the basic approach to interpretation of EKG strips
Discuss the five steps used in interpretation of EKG strips

3. Interpretation of an EKG Strip
Objectives
Explain how to calculate heart rate, given a 6-second strip
Name four causes of artifact

4. 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

5. 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

6. General Rules
Master the accepted parameters for each dysrhythmia and apply them to each of the five steps when analyzing the strip

7. 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

8. 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

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

10. Heart Rate Determination
Two methods of determination of the heart rate
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

11. Sample of 6-Second Method

12. Two Methods to Determine Heart Rate
Two methods of determination of the heart rate
Second method is the R-R interval method
Most accurate if heart rate is regular
An estimation of the heart rate

13. Two Methods to Determine Heart Rate
Two methods of determination of the heart rate
Second method is the R-R interval method
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

14. Sample Strip for R - R Method

15. STEP 2: Heart Rhythm Rhythm
Sequential beating of the heart as a result of the generation of electrical impulses

16. STEP 2: Heart Rhythm Classified as Regular pattern Irregular pattern
Intervals between R waves are regular
Irregular pattern
Intervals between R waves are not regular

17. Regular Rhythm
Measure the intervals between P to P waves or R to R waves

18. Regular Rhythm
If the intervals vary by less than 0.06 seconds or 1.5 small boxes, we can consider the rhythm to be regular

19. 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
Regularly irregular
Irregular rhythms that occur in a pattern
Occasionally irregular
Intervals of only one or two R to R are uneven

20. 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

21. Practice Strip for Rate and Rhythm Analysis

22. Practice Strip for Rate and Rhythm Analysis

23. 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

24. STEP 3: The P Wave

25. 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?

26. P Wave: Five Questions to Ask
Step 4: Are the P waves smooth, rounded,and upright in appearance, or are they inverted?
Step 5: Do all P waves look similar?

27. P Wave Practice Strip

28. 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 0.12–0.20 seconds (3–5 small squares)

29. STEP 4: The PR Interval

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

31. PR Interval Practice Strip

32. STEP 5: The QRS Complex

33. 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)

34. STEP 5: The QRS Complex
Represents depolarization or contraction of the ventricles
S wave
The sharp, negative, or downward deflection that follows the R wave

35. QRS Complex: 3 Questions to Ask
Are QRS intervals greater than 0.12 seconds (wide)?
Are QRS intervals less than 0.12 seconds (narrow)?
Are the QRS complexes similar in appearance across the EKG strip?

36. Sample QRS Rhythm Strip

37. The ST Segment

38. 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

39. The ST Segment
If ST segment is elevated or depressed, myocardial ischemia or injury may be indicated

40. The T Wave

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

42. 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

43. Artifact
EKG waveforms from sources outside the heart

44. Artifact Interference seen on a monitor or EKG strip 4 causes
Patient movement
Loose or defective electrodes (fuzzy baseline)
Improper grounding (60 cycle interference)
Faulty EKG apparatus

45. Sample Rhythm Strip of Artifact