Understanding Basic EKG

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
Pulmonary Trunk
Right Left Pulmonary Arteries
Lungs
Pulmonary Veins
Left Atrium
7

Mitral Valve

Left Ventricle
Aortic Semi-lunar Valve
Aorta
Body
8
Right Coronary Artery

• supplies blood to
• Right Atrium
• Right Ventricle
• the SA Node in 55 of population the LV inferior
  wall
• the LV posterior wall and ? 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
• ? 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 ? 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 persons 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
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
• 60-100 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
Cardiac Conduction 101

• Lets look at a normal conduction pathway

20
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
Cardiac Conduction 101

• Pacemaker Cells are very small cells within the
  conduction system which spontaneously generate
  electrical impulses.
• Pacemaker Power Source (Brain)

22
Cardiac Conduction 101

• Electrical Conducting Cells rapidly carry current
  to all areas of the heart.
• Conducting Cells Hard Wiring of Heart
• (Fuel)

23
Cardiac Conduction 101

• Now, lets 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
Cardiac Conduction 101

• The QT interval measures the time from the start
  of ventricular depolarization to the end of
  ventricular repolarization.
• QT interval lt 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
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
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
• Whats 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 QRSs 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
EKG Rate Computation

• Rules
• Memorize these numbers
• 300, 150, 100, 75, 50
• Normal Heart rate for an adult 60 -100 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
EKG Rate Analysis

• Lets 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? gt 0.10
• Is it normal?
• QRS 0.08 0.10 seconds
• Or is it narrow? lt 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 lt 0.43 seconds?
• Is there any ectopy present?

50
EKG Interpretation

• Lets 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,
  its normal
• 6. Is the ST segment elevated or depressed? No
• 7. Is the QT Interval lt 0.43? Yes, QT Interval
  0.36

52
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 gt 350 bpm Ventricular is 120-200
  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 250-350 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
Cardiac Arrhythmias

• Ventricular Fibrillation
• Figure 13
• Rhythm Totally erratic
• VF Rate 350-450 bpm
• P-waves none
• QRS none

58
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 gt 0.12 seconds with an odd, tomb stone
  shape

59
Cardiac Arrhythmias

• 3rd Degree AV Block Complete Heart Block
• Figure 15
• Rate 40-60 bpm (narrow QRS and junctional)
  20-40 bpm (wide QRS and ventricular)
• P-waves normal, but usually more P-waves than
  QRSs

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 http//images.google.com/imgres?imgurlh
  ttp//www.micardia.com/images/anatomy-of-the-human
  -heart.jpgimgrefurlhttp//www.micardia.com/CHF-C
  ongestive-Heart-Failure/Structural-heart-disease-a
  nd-mitral-prolapses.phpusg__vAFkAZBOMi2yoKCxSP0R
  39jzRQEh324w250sz48hlenstart288um1tb
  nidzVIu6UfvBI-h2Mtbnh118tbnw91prev/images
  3Fq3Dblood2Bflow2Bthrough2Bheart26ndsp3D182
  6hl3Den26sa3DN26start3D27026um3D1
• Figure 2. (2008). Image retrieved on February
  15, 2009 from http//2.bp.blogspot.com/_2MjIeQJj8U
  M/SPjvLvdNZPI/AAAAAAAAAJA/7KNEAG5TcIY/s1600-h/limb
  leads.jpg
• Figure 3. (2008). Image retrieved on February 15,
  2009 from http//2.bp.blogspot.com/_2MjIeQJj8UM/ST
  qKlrU3dpI/AAAAAAAAAa4/anAGFWaQrRQ/s1600-h/ecg08_f8
  b.jpg

62
References

• Figure 4.(2008). Image retrieved on February 15,
  2009 from http//www.szivorvos.hu/english/wp-conte
  nt/gallery/pictures-and-photos-of-heart/electrical
  -system-of-the-heart.jpg
• Figure 5. (2004). Image retrieved on February 16,
  2009 from http//www.ncbi.nlm.nih.gov/bookshelf/br
  .fcgi?bookcardiopartA39
• Figure 6. (2002). Image retrieved on February 16,
  2009 from http//www.a-fib.com/EKGsignal.htm
• Figure 7. (2006). Image retrieved on February 16,
  2009 from http//www.ambulancetechnicianstudy.co.u
  k/images/ecg_paper1.gif
• Figure 8. (2008). Image retrieved on February 17,
  2009 from http//ems12lead.blogspot.com/2008/11/la
  rge-block-method-for-heart-rate.html

63
References

• Figure 9. (2006). Image retrieved on March 1,
  2009 from http//www.ambulancetechnicianstudy.co.
  uk/rhythms.html
• Figure 10. (2008). Image retrieved on March 1.
  2009 from http//www.rnlife.com/wp-content/uploads
  /2008/11/ekg-strip.jpg
• Figure 11. (2008). Image retrieved on March 1,
  2009 from http//www.heartyhealth.com/CV/training/
  a-fib.html
• Figure 12. (2004). Image retrieved on March 1,
  2009 from http//www.ncbi.nlm.nih.gov/bookshelf/br
  .fcgi?bookcardiopartA39
• Figure 13. (n.d.). Image retrieved on March 1,
  2009 from http//www.cs.iupui.edu/stewarte/N241/v
  fib.jpg
• Figure 14. (n.d.). Image retrieved on March 1,
  2009 from http//www.cs.iupui.edu/stewarte/N241/v
  fib.jpg

64
References

• Figure 15. (2005). Image retrieved on March 1,
  2009 from http//www.pacemakerproject.com/assets/i
  mg/thirdAV_ecg.jpg
• Figure 16. (2006). Image retrieved on march 1,
  2009 from http//www.ambulancetechnicianstudy.co.u
  k/images/Asystole.gif
• Huff, J. (2002). Ecg workout exercises in
  arrhythmia interpretation. Philadelphia, PA
  Lippincott, Williams Wilkins.
• Prehospital 12 Lead ECG. (2008). Retrieved on
  March 10, 2009 from http//ems12lead.blogspot.co
  m/2008/11/large-block-method-for-heart-rate.html
• Smeltzer, S. C. Bare, B. G. (2004). Brunner
  Suddarths textbook of medical surgical nursing.
  (10th ed.). Philadelphia, PA Lippincott,
  Williams Wilkins.

65
References

• Thaler, M. (2003). The only ekg book youll 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 !!!