1. Understanding Basic EKG
Zabrina Bellina
University of Central Florida
Teaching With Technology Project

2. Objectives:
At the conclusion of this presentation, students will able to:
1. Describe coronary circulation and gain working knowledge of blood supply to heart structures.
Define the term electrocardiography and describe the electrical conduction system of the heart.

3. Objectives
Correlate electrical events in the heart with the waveform represented in a normal EKG.
Gain understanding of EKG interpretation through waveform measurement, analysis, and correct rate computation of rhythm strips.
Understand and identify lethal cardiac arrhythmia waveforms.

4. Coronary Circulation Review
Figure 1

5. Coronary Circulation Review
Superior & Inferior Vena Cava
Right Atrium
Tricuspid Valve
Right Ventricle
Pulmonary Semi-lunar Valve

6. Right & Left Pulmonary Arteries
Pulmonary Trunk
Right & Left Pulmonary Arteries
Lungs
Pulmonary Veins
Left Atrium

7. Aortic Semi-lunar Valve
Mitral Valve
Left Ventricle
Aortic Semi-lunar Valve
Aorta
Body

8. Right Coronary Artery Right Atrium Right Ventricle
supplies blood to:
Right Atrium
Right Ventricle
the SA Node in 55% of population the LV inferior wall
the LV posterior wall and ⅓ of the posterior interventricular septum in 90% of the population

9. Left Circumflex Artery
supplies blood to:
the Left Atrium
the LV lateral wall
the SA Node in 45% of the population and to
the LV posterior wall
⅓ of the interventricular septum
AV Node and Bundle of His in 10% of the population

10. Left Anterior Descending Artery
supplies blood to:
the LV anterior and lateral walls
the Left and Right Bundle Branches
the anterior ⅔ of the interventricular septum

11. Coronary Artery Blood Supply
Remember:
The Right Coronary Artery supplies both the Right and Left heart.
The Left Coronary Artery and its branches only supply the Left heart.

12. What is an EKG?
An electrocardiogram (ECG) , also known as an EKG, is a graphic recording of the electrical activity of the heart. It is used as a diagnostic tool to assess cardiac function.

13. Electrocardiogram
An EKG is a painless procedure that can be performed by placing disposable electrodes on the skin of a person’s chest wall, upper and lower extremities.
Figure 2 Figure 3

14. Electrocardiogram
An EKG can be recorded with 12, 15, and sometimes even 18 leads. However, the 12 lead EKG is the most commonly used tool to diagnose cardiac conduction abnormalities, arrhythmias, myocardial infarction and ischemia.

15. Electrocardiogram Remember,
an EKG represents the electrical impulses that the heart transmits and are recorded as tracings on specialized graph paper.

16. The Conduction System of the Heart
Cardiac Conduction 101
The Conduction System of the Heart
Figure 4

17. Cardiac Conduction 101
The SA Node is the primary pacemaker for the heart at
beats/minute
The AV Node is the “back-up” pacemaker of the heart at
40-60 beats/ minute

18. Cardiac Conduction 101
The Ventricles (bundle branches & Purkinje fibers)
are the last resort and maintain an
intrinsic rate of only
20-40 beats/minute

19. Let’s look at a normal conduction pathway:
Cardiac Conduction 101
Let’s look at a normal conduction pathway:
SA Node
AV Node
Bundle of His
Right and Left Bundle Branches
Purkinje Fibers
Myocardial
Contraction

20. Myocardial = Muscle (Brawn)
Cardiac Conduction 101
Myocardial Cells = the mechanical cells of the heart. They contract when they receive an electrical impulse from the pacemaker cells.
Myocardial = Muscle (Brawn)

21. Pacemaker = Power Source (Brain)
Cardiac Conduction 101
Pacemaker Cells are very small cells within the conduction system which spontaneously generate electrical impulses.
Pacemaker = Power Source (Brain)

22. Conducting Cells = Hard Wiring of Heart
Cardiac Conduction 101
Electrical Conducting Cells rapidly carry current to all areas of the heart.
Conducting Cells = Hard Wiring of Heart
(Fuel)

23. Ventricles depolarize
Cardiac Conduction 101
Now, let’s correlate the mechanical activity with the electrical activity….
Figure 5
Ventricular Systole
Atrial Systole
Ventricles repolarize
Atria depolarize
Ventricles depolarize

24. Cardiac Conduction 101
Depolarization occurs when sodium channels open fast and the inside of the membrane becomes less negative (electrical stimulation).
This is manifested as the P wave on an EKG, which signifies atrial muscle depolarization.

25. Cardiac Conduction 101
The plateau that immediately follows the P wave represents atrial systole, when calcium channels open slowly and potassium channels close (at this time mechanical contraction of the atria takes place).

26. Cardiac Conduction 101
The PR interval on an EKG reflects conduction of an electrical impulse from the SA node through the AV node.
PR = 0.12 – 0.20 seconds
Figure 6

27. Cardiac Conduction 101
The QRS complex of an EKG reflects ventricular muscle depolarization (the electrical impulse moves through the Bundle of His, the left and right bundle branches and Purkinje fibers).
QRS = 0.08 – 0.10 seconds

28. QT interval = < 0.43 seconds or ½ of the R-to-R interval
Cardiac Conduction 101
The QT interval measures the time from the start of ventricular depolarization to the end of ventricular repolarization.
QT interval = < 0.43 seconds or
½ of the R-to-R interval

29. Cardiac Conduction 101
The ST segment reflects the early ventricular repolarization and lasts from the end of the QRS complex to the beginning of the T wave.

30. Cardiac Conduction 101
The T-wave on an EKG reflects ventricular muscle repolarization (when the cells regain a negative charge - the “resting state”) and mechanical relaxation, which is also known as diastole.

31. Keep in mind how electricity flows…
EKGs Revisited
Keep in mind how electricity flows…
When an electrical current moves toward a positive electrode, the deflection on the EKG strip will be positive (up).
When an electrical current moves toward a negative electrode, the deflection on the EKG strip will be negative(down).

32. EKGs Revisited ST Segment Changes
Any elevation in the ST segment that is greater than two small boxes is indicative of myocardial injury.
Any ST segment depression greater than two small boxes indicates myocardial ischemia.

33. EKG Paper
EKG paper comes in a roll of graph paper consisting of horizontal and vertical light and dark lines.
The horizontal axis measures time
Figure 7
The vertical axis measures voltage

34. One small square = 0.04 seconds One large square = 0.2 seconds
EKG Paper
One small square = 0.04 seconds
One large square = 0.2 seconds or
One small square(0.04) x 5

35. EKG Paper The light lines circumscribe small squares of 1 x 1 mm
One small square = 0.1 mV
The dark lines delineate
large squares of 5 x 5 mm
One large square = 0.5 mV

36. EKG Analysis
Rhythm
Rate
P - waves
PR Interval
QRS Complex

37. EKG Rate Analysis Rate 60 – 100 beats/ minute
What’s the normal heart rate for an adult human being?
60 – 100 beats/ minute
Is the rate in your strip too fast or too slow?

38. EKG Rate Analysis
In terms of rate computation, heart rate generally refers to the number of ventricular contractions that occur in 60 seconds or one minute.
When calculating rates, if there is a P-wave in front of every R-wave, the atrial and ventricular rates will be the same. .

39. EKG Rate Analysis
Atrial rate can be calculated by measuring the interval of time between P-waves (the P-to-P intervals).
Ventricular rate can be calculated by measuring the time intervals between QRS complexes (the R-to-R intervals).

40. EKG Rate Analysis
There are instances, such as 2nd and 3rd degree AV block, in which the atrial rate and ventricular rates are different.
This is why it is important to know how to determine both atrial and ventricular rates.

41. EKG Rate Computation Rules
Count the number of QRS’s in a 6 - second strip, then multiply that number by 10.
Determine the time between R-R intervals, then divide that number by 60.
For example:
40 ÷ (20 small boxes x 0.04 seconds each)
= 50 beats per minute

42. Memorize these numbers:
EKG Rate Computation
Rules
Memorize these numbers:
300, 150, 100, 75, 50
Normal Heart rate for an adult = bpm
This means that 3 to 5 large blocks should exist between R – R intervals.
Bradycardia = more than 5 large blocks
Tachycardia = less than 3 large blocks

43. EKG Rate Computation
Figure 8

44. Let’s Practice with an Example: What is the rate based on Rule #1?
EKG Rate Analysis
Let’s Practice with an Example:
Figure 9
What is the rate based on Rule #1?
If you said 50 bpm….
You are Correct!!!

45. EKG Rhythm Analysis Questions:
Are the P waves regular or irregular?
Are the R-to-R intervals regular or irregular?

46. EKG P-wave Analysis Questions:
Are there P-waves in your rhythm strip?
Is there a P-wave for each QRS complex?
Do all of the P-waves look the same?

47. EKG PR Interval Analysis Questions:
Is the PR Interval measurement normal?
PR = 0.12 – 0.20 seconds
Is the PR Interval measurement constant?

48. EKG QRS Analysis Questions:
Is the QRS wide? > 0.10
Is it normal?
QRS = 0.08 – 0.10 seconds
Or is it narrow? < 0.08

49. EKG Analysis Questions:
Is the T-wave peaked, inverted or flat?
Is the ST segment elevated, depressed or normal?
Is the QT Interval < 0.43 seconds?
Is there any ectopy present?

50. EKG Interpretation Let’s try an example….. Figure 10
Is the rhythm regular or irregular? Regular
Are the P-waves identical? Is there a P-wave for each QRS complex? Yes for both!
Is the PR Interval 0.12 – 0.20? Yes, PR = 0.16

51. EKG Interpretation continued…
Is the QRS wide, normal or narrow?
Normal QRS = 0.08
5. Is the T-wave peaked, inverted or flat? No, it’s normal
6. Is the ST segment elevated or depressed? No
7. Is the QT Interval < 0.43? Yes, QT Interval= 0.36

52. And last but not least, is there any ectopy present in this rhythm?
EKG Interpretation
And last but not least, is there any ectopy present in this rhythm?
NO!

53. EKG Interpretation
And the rhythm is….
Normal Sinus Rhythm

54. Cardiac Arrhythmias
Listed below are the cardiac arrhythmias that are almost always associated with death:
Atrial Fibrillation
Atrial Flutter
Ventricular Fibrillation
Ventricular Tachycardia
3rd degree AV Block
Asystole

55. Cardiac Arrhythmias Atrial Fibrillation Figure 11
Rhythm: Atrial fibrillation is irregular and chaotic; Ventricular rhythm is very irregular
Rate: Atrial is > 350 bpm; Ventricular is bpm
P-waves: not consistent (they are fine and fibrillating)
PR Interval: not measurable

56. Cardiac Arrhythmias Atrial Flutter
Figure 12
Rhythm: Atrial flutter is usually regular
Rate: Atrial is bpm
Ventricular rate depends on AV conduction
P-waves: characterized by “saw tooth” pattern
PR Interval: can not be determined; more flutter waves than QRS complexes

57. Ventricular Fibrillation
Cardiac Arrhythmias
Ventricular Fibrillation
Figure 13
Rhythm: Totally erratic
VF Rate: bpm
P-waves: none
QRS: none

58. Ventricular Tachycardia
Cardiac Arrhythmias
Ventricular Tachycardia
Figure 14
aka “The Widow-Maker”
Rhythm: Typically regular, but can be irregular
Rate: 100 – 220 bpm
P-waves: can be present but have no correlation to QRS complex
QRS: > 0.12 seconds with an odd, “tomb –stone” shape

59. 3rd Degree AV Block = Complete Heart Block
Cardiac Arrhythmias
3rd Degree AV Block = Complete Heart Block
Figure 15
Rate: bpm (narrow QRS and junctional); bpm (wide QRS and ventricular)
P-waves: normal, but usually more P-waves than QRS’s

60. Cardiac Arrhythmias Asystole Figure 16
In Asystole, there is no rate because the person that belongs to this rhythm is DEAD!

61. References
Figure 1. (2009). Image retrieved on February 17, 2009 from
Figure 2. (2008). Image retrieved on February 15, 2009 from
Figure 3. (2008). Image retrieved on February 15, 2009 from

62. References
Figure 4.(2008). Image retrieved on February 15, 2009 from
Figure 5. (2004). Image retrieved on February 16, 2009 from
Figure 6. (2002). Image retrieved on February 16, 2009 from
Figure 7. (2006). Image retrieved on February 16, 2009 from
Figure 8. (2008). Image retrieved on February 17, 2009 from

63. References
Figure 9. (2006). Image retrieved on March 1, 2009 from
Figure 10. (2008). Image retrieved on March from
Figure 11. (2008). Image retrieved on March 1, 2009 from
Figure 12. (2004). Image retrieved on March 1, 2009 from
Figure 13. (n.d.). Image retrieved on March 1, 2009 from
Figure 14. (n.d.). Image retrieved on March 1, 2009 from

64. References
Figure 15. (2005). Image retrieved on March 1, 2009 from
Figure 16. (2006). Image retrieved on march 1, 2009 from
Huff, J. (2002). Ecg workout exercises in arrhythmia interpretation. Philadelphia, PA: Lippincott, Williams & Wilkins.
Prehospital 12 Lead ECG. (2008). Retrieved on March 10, from
Smeltzer, S. C. & Bare, B. G. (2004). Brunner & Suddarth’s textbook of medical surgical nursing. (10th ed.). Philadelphia, PA: Lippincott, Williams & Wilkins.

65. References
Thaler, M. (2003). The only ekg book you’ll ever need. (4th ed.). Philadelphia, PA: Lippincott, Williams & Wilkins.
White, K. (2007). Fast facts for adult critical care. Mobile, AL: Kathy White Learning Systems.
The End !!!