Interpreting ecg

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EASY WAY TO UNDERSTAND HOW TO INPERPRET ECGs.

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Interpreting ecg

  1. 1. Interpreting ECG
  2. 2. 1. Coronary circulation. 2. Electrical conduction system of the heart 3. Electrocardiography elements 4. Electrical events & the waveform in a normal ECG. 5. ECG interpretation 6. Identify lethal cardiac diseases 7. The learning
  3. 3. Coronary circulation
  4. 4.  Figure 1
  5. 5. Superior & Inferior Vena Cava Right Atrium Tricuspid Valve Right Ventricle Pulmonary Semi-lunar Valve
  6. 6. PulmonaryTrunk Right & Left Pulmonary Arteries Lungs Left Atrium PulmonaryVeins
  7. 7. MitralValve LeftVentricle Aortic Semi-lunarValve Aorta Body
  8. 8.  Supplies blood to:  Right Atrium  Right Ventricle  The SA Node and 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. 9.  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. 10.  Supplies blood to:  the LV anterior and lateral walls  the Left and Right Bundle Branches  the anterior ⅔ of the interventricular septum
  11. 11.  Recall:  The Right Coronary Artery supplies both the Right and Left heart.  The Left Coronary Artery and its branches only supply the Left heart.
  12. 12. Electrical conduction of the heart
  13. 13.  The Conduction System of the Heart
  14. 14.  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.  The Ventricles (bundle branches & Purkinje fibers) are the last resort and maintain an intrinsic rate of only 20-40 beats/minute
  15. 15.  The normal conduction pathway: SA Node AV Node Bundle of His Right & Left Bundle Branches Purkinje Fibers Myocardial Contraction
  16. 16.  Correlation of the mechanical activity with the electrical activity….
  17. 17.  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 ECG, which signifies atrial muscle depolarization.  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).
  18. 18.  The PR interval on an ECG reflects conduction of an electrical impulse from the SA node through the AV node.  PR = 0.12 – 0.20 seconds
  19. 19.  The QRS complex of an ECG 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  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.
  20. 20.  The ST segment reflects the early ventricular repolarization and lasts from the end of the QRS complex to the beginning of the T wave.  The T-wave on an ECG reflects ventricular muscle repolarization (when the cells regain a negative charge - the “resting state”) and mechanical relaxation, which is also known as diastole.
  21. 21. ECG elements
  22. 22.  Myocardial Cells = the mechanical cells of the heart. They contract when they receive an electrical impulse from the pacemaker cells.  Myocardial = Muscle  Pacemaker Cells are very small cells within the conduction system which spontaneously generate electrical impulses.  Pacemaker = Power Source  Electrical Conducting Cells rapidly carry current to all areas of the heart.  Conducting Cells = Hard Wiring of Heart
  23. 23.  An electrocardiogram (ECG) is a graphic recording of the electrical activity of the heart.  The machine is called Electrocardiograph while the recording is called Electocardiogram & is used as a diagnostic tool to assess cardiac function..
  24. 24.  ECG paper comes in a roll of graph paper consisting of horizontal and vertical light and dark lines.  The horizontal axis measures time    The vertical axis measures voltage.
  25. 25.  One small square = 0.04 seconds    One large square = 0.2 seconds Or [One small square(0.04)] x 5
  26. 26.  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
  27. 27.  ECG is a painless procedure that is performed by placing disposable electrodes on the skin of a person’s chest wall, upper & lower extremities.  In the ECG, the 12 lead one is the most commonly used tool to diagnose cardiac conduction abnormalities, arrhythmias, myocardial infarction and ischemia.
  28. 28.  The ECG represents the electrical impulses that the heart transmits and are recorded as wave tracings on specialized graph paper.
  29. 29.  6 limb leads  6 precordial leads  Positioning measures 12 perspectives or views of the heart  The 12 perspectives are arranged in vertical columns  Limb leads are I, II, III, AVR, AVL, AVF  Precordial leads are V1, V2, V3, V4, V5, V6  Horizontal marks time  Vertical marks amplitude
  30. 30.  Each limb lead I, II, III, AVR, AVL, AVF records from a different angle  All 6 limb leads intersect and visualize a frontal plane  The 6 chest leads (precordial) V1, V2, V3, V4, V5, V6 view the body in the horizontal plane to the AV node  The 12 lead ECG forms a camera view from 12 angles
  31. 31. I and AVL II, III and AVF V3 & v4 V1 & v2 V5 & v6 Where the positive electrode is positioned, determines what part of the heart is seen!
  32. 32.  Each positive electrode acts as a camera looking at the heart  10 leads attached for 12 lead diagnostics. The monitor combines 2 leads.  Mnemonic for limb leads  White on right  Smoke(black) over fire(red)  Snow(white) on grass(green)
  33. 33.  Limb leads I, II, III are bipolar and have a negative and positive pole  Electrical potential differences are measured between the poles  AVR, AVL and AVF are unipolar  No negative lead  The heart is the negative pole  Electrical potential difference is measured betweeen the lead and the heart  Chest leads are unipolar  The heart also is the negative pole
  34. 34.  Anteroseptal: V1, V2, V3, V4  Anterior: V1–V4  Anterolateral: V4–V6, I, aVL  Lateral: I and aVL  Inferior: II, III, and aVF  Inferolateral: II, III, aVF, and V5 and V6
  35. 35.  Anteroseptal: V1, V2, V3, V4  Anterior: V1–V4  Anterolateral: V4–V6, I, aVL  Lateral: I and aVL  Inferior: II, III, and aVF  Inferolateral: II, III, aVF, and V5 and V6
  36. 36.  Yellow indicates V1, V2, V3, V4  Anterior infarct with ST elevation  Left Anterior Descending Artery (LAD)  V1 and V2 may also indicate septal involvement which extends from front to the back of the heart along the septum  Left bundle branch block  Right bundle branch block  2nd Degree Type2  Complete Heart Block
  37. 37.  Blue indicates leads II, III, AVF  Inferior Infarct with ST elevations  Right Coronary Artery (RCA)  1st degree Heart Block  2nd degree Type 1, 2  3rd degree Block  N/V common, Brady 2004 Anna Story 40
  38. 38.  Red indicates leads I, AVL, V5, V6  Lateral Infarct with ST elevations  Left Circumflex Artery  Rarely by itself  Usually in combo
  39. 39.  Green indicates leads V1, V2  Posterior Infarct with ST  Depressions and/ tall R wave  RCA and/or LCX Artery  Understand Reciprocal changes  The posterior aspect of the heart is viewed as a mirror image and therefore depressions versus elevations indicate MI  Rarely by itself usually in combo
  40. 40.  No color for SubEndocardial infarcts since they are not transmural  Look for diffuse or localized changes and non – Q wave abnormalities  T-wave inversions  ST segment depression
  41. 41.  A combination of infarcts such as:  Anterolateral yellow and red  Inferoposterior blue and green  Anteroseptal yellow and green
  42. 42.  Anteroseptal: V1, V2, V3, V4  Anterior: V1–V4  Anterolateral: V4–V6, I, aVL  Lateral: I and aVL  Inferior: II, III, and aVF  Inferolateral: II, III, aVF, and V5 and V6
  43. 43.  When an electrical current moves toward a positive electrode, the deflection on the ECG strip will be positive (up).  When an electrical current moves toward a negative electrode, the deflection on the ECG strip will be negative(down).
  44. 44. Electrical events and the waveform in ECG
  45. 45.  Rate  Rhythm (including intervals and blocks)  P - waves  PR Interval  QRS Complex  Axis  Hypertrophy  Ischemia
  46. 46.  Rate  Rhythm (including intervals and blocks)  P - waves  PR Interval  QRS Complex  Axis  Hypertrophy  Ischemia
  47. 47.  Rate  What’s the normal heart rate for an adult human being? ▪ 60 – 100 beats/ minute  Remember:  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.
  48. 48.  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).  Check:  Is the rate in the strip too fast or too slow?
  49. 49.  Why is it necessary to know both the atrial and ventricular rates?  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.
  50. 50.  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
  51. 51.  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.
  52. 52.  Rule of 300- Divide 300 by the number of boxes between each QRS = rate  HR of 60-100 = normal  HR > 100 = tachycardia  HR < 60 = bradycardia
  53. 53.  Let’s Practice with an Example:  What is the rate based on Rule #1?  If it is 50 bpm…., you are Correct!!!
  54. 54.  Let’s Practice with an Example:  What is the rate based on Rule #1?  300/6= 50 bpm
  55. 55.  Rate  Rhythm (including intervals and blocks)  P - waves  PR Interval  QRS Complex  Axis  Hypertrophy  Ischemia
  56. 56.  Sinus  Originating from SA node  P wave before every QRS  P wave in same direction as QRS
  57. 57.  PR  0.20 sec (less than one large box)  QRS  0.08 – 0.10 sec (1-2 small boxes)  QT  450 ms in men, 460 ms in women  Based on sex / heart rate  Half the R-R interval with normal HR
  58. 58.  Normal  Men 450ms  Women 460ms  Corrected QT (QTc)  QTm/√(R-R)  Causes  Drugs (Na channel blockers)  Hypocalcemia, hypomagnesemia, hypokalemia  Hypothermia  AMI  Congenital  Increased ICP
  59. 59.  AV blocks 1. First degree block ▪ PR interval fixed and > 0.2 sec 2. Second degree block, Mobitz type 1 ▪ PR gradually lengthened, then drop QRS 3. Second degree block, Mobitz type 2 ▪ PR fixed, but drop QRS randomly 4. Type 3 block ▪ PR and QRS dissociated
  60. 60.  Are the P waves regular or irregular?  Are the R-to-R intervals regular or irregular?
  61. 61.  Rate  Rhythm (including intervals and blocks)  P - waves  PR Interval  QRS Complex  Axis  Hypertrophy  Ischemia
  62. 62.  Are there P-waves in the rhythm strip?  Is there a P-wave for each QRS complex?  Do all of the P-waves look the same?
  63. 63.  Rate  Rhythm (including intervals and blocks)  P - waves  PR Interval  QRS Complex  Axis  Hypertrophy  Ischemia
  64. 64.  Is the PR Interval measurement normal?  PR = 0.12 – 0.20 seconds  Is the PR Interval measurement constant?
  65. 65.  Rate  Rhythm (including intervals and blocks)  P - waves  PR Interval  QRS Complex  Axis  Hypertrophy  Ischemia
  66. 66.  Is the QRS wide? > 0.10  Is it normal?  QRS = 0.08 – 0.10 seconds  Or is it narrow? < 0.08
  67. 67.  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?
  68. 68.  Rate  Rhythm (including intervals and blocks)  P - waves  PR Interval  QRS Complex  Axis  Hypertrophy  Ischemia
  69. 69.  Represents the overall direction of the heart’s activity and Axis of –30 to +90 degrees is normal.
  70. 70.  QRS up in I and up in aVF = Normal
  71. 71.  Normal- QRS up in I and aVF
  72. 72.  Add the larger S wave of V1 or V2 in mm, to the larger R wave of V5 or V6.  Sum is > 35mm = LVH
  73. 73.  Rate  Rhythm (including intervals and blocks)  P - waves  PR Interval  QRS Complex  Axis  Hypertrophy  Ischemia
  74. 74.  Ischaemia…..  Usually indicated by ST segment changes 1. Elevation = Infarction ▪ Any elevation in the ST segment that is greater than 2 small boxes is indicative of myocardial injury. 2. Depression = Ischemia ▪ Any ST segment depression greater than 2 small boxes indicates myocardial ischemia.  Can manifest as T wave changes  Remote ischemia shown by Q waves
  75. 75.  T-wave inversion ( flipped T)  ST segment depression  T wave flattening  Biphasic T-waves Baseline
  76. 76.  ST segment elevation of greater than 1mm in at least 2 contiguous leads  Heightened or peaked T waves  Directly related to portions of myocardium rendered electrically inactive Baseline
  77. 77.  Significant Q-wave where none previously existed  Why? ▪ Impulse traveling away from the positive lead ▪ Necrotic tissue is electrically dead  No Q-wave in Subendocardial infarcts  Why? ▪ Not full thickness dead tissue ▪ But will see a ST depression ▪ Often a precursor to full thickness MI  Criteria  Depth of Q wave should be 25% the height of the R wave  Width of Q wave is 0.04 secs  Diminished height of the R wave
  78. 78. 1 year Q wave ST Elevation T wave inversion
  79. 79. ECG interpretation
  80. 80.  Let’s try an example….. Is the rhythm regular or irregular? Are the P-waves identical? Is there a P- wave for each QRS complex? Is the PR Interval 0.12 – 0.20? Regular Yes for both! Yes, PR = 0.16
  81. 81.  Let’s try an example….. Is the Is the QRS wide, normal or narrow?? Is the T-wave peaked, inverted or flat? Is the ST segment elevated or depressed? Is the QT Interval < 0.43? Normal QRS = 0.08 No, it’s normal No Yes, QT Interval= 0.36
  82. 82.  Is there any ectopy present in this rhythm? No
  83. 83.  So, the rhythm is ….. Normal sinus rhythm
  84. 84. Identify lethal cardiac diseases
  85. 85.  The cardiac arrhythmias that are almost always associated with death include: 1. Atrial Fibrillation 2. Atrial Flutter 3. Ventricular Fibrillation 4. Ventricular Tachycardia 5. 1st , 2nd and 3rd degree AV Block 6. Asystole 7. Ischaemia
  86. 86.  Atrial fibrillation….. Rhythm Rate P-waves PR interval Atrial fibrillation is irregular + chaotic; Ventricular rhythm is very irregular Atrial is > 350 bpm; Ventricular is 120- 200 bpm Not consistent (they are fine and fibrillating) Not measurable
  87. 87.  Atrial flutter….. Rhythm Rate P-waves PR interval Atrial flutter is usually regular; Atrial is 250- 350 bpm; Ventricular rate depends on AV conduction characterized by “saw tooth” pattern cannot be determined; more flutter waves than QRS complexes
  88. 88.  Ventricular fibrillation….. Rhythm Rate P-waves PR interval Ventricular rhythm is totally erratic Ventricular rate is 350-450 bpm None None
  89. 89.  Ventricular tachycardia….. Aka widow maker Rhythm Rate P-waves PR interval Typically regular, but can be irregular Ventricular rate is 100-220 bpm can be present but have no correlation to QRS complex 0.12 seconds with odd “tomb –stone” shape
  90. 90.  Type 1st degree AV block  PR is fixed and longer than 0.2 sec
  91. 91.  Type 1 - 2nd degree AV block [Wenckebach]
  92. 92.  Type 2 - 2nd degree AV block Dropped QRS
  93. 93.  3rd degree AV block….. Complete heart block Rhythm Rate P-waves PR interval 40-60 bpm (narrow QRS and junctional); 20-40 bpm (wide QRS and ventricular) Normal, but usually more P-waves than QRS’s
  94. 94.  Asystole….. Rhythm Rate P-waves PR interval No rate as the person that belongs to this rhythm is DEAD
  95. 95.  What is the diagnosis….. Acute inferior MI with ST elevation in leads II, III, aVF
  96. 96.  What is the diagnosis….. ST depression II, III, aVF, V3-V6 = ischemia
  97. 97.  What is the diagnosis….. Anterior MI with lateral involvement ST elevations V2, V3, V4 ST elevations II, AVL, V5
  98. 98.  What is the diagnosis….. Anteroseptal MI ST elevations V1, V2, V3, V4
  99. 99.  What is the diagnosis….. Inferior MI ST elevation 2,3 AVF
  100. 100.  What is the diagnosis….. Inferior lateral MI ST elevations 2, 3, AVF ST elevations V5
  101. 101.  What is the diagnosis….. Acute inferior MI Lateral ischemia
  102. 102. Sample ECGs
  103. 103. Narrow complex, regular; retrograde P waves, rate <220
  104. 104.  (Wenckebach) PR interval fixed, QRS dropped intermittently
  105. 105. Monophasic R wave in I and V6, QRS > 0.12 sec; Loss of R wave in precordial leads; QRS T wave discordance I, V1, V6; Consider ischemia if a new finding
  106. 106. V1: RSR prime pattern with inverted T wave V6: Wide deep slurred S wave
  107. 107. Ventricular escape rhythm, 40-110 bpm; Seen in AMI, a marker of reperfusion
  108. 108. Rate 40-60, no p waves, narrow complex QRS
  109. 109. Tall, narrow and symmetric T waves
  110. 110. U waves Can also see PVCs, ST depression, small T waves
  111. 111. ST elevation & biphasic T wave in V2 and V3;Sign of large proximal LAD lesion
  112. 112. Short PR interval <0.12 sec; Prolonged QRS >0.10 sec; Delta wave Can simulate ventricular hypertrophy, BBB and previous MI
  113. 113. RBBB or incomplete RBBB in V1-V3 with convex ST elevation
  114. 114.  Autosomal dominant genetic mutation of Na+ channels  Causes syncope, v-fib, self terminating VT, and sudden cardiac death  Can be intermittent on ECG  Most common in middle-aged males  Can be induced in EP lab  Need ICD
  115. 115. Trigeminy pattern
  116. 116. Sawtooth waves; Typically at HR of 150
  117. 117. Notice twisting pattern Treatment: Magnesium 2 grams IV
  118. 118. Reciprocal changes
  119. 119. ST elevation II, III, aVF ST depression in aVL, V1-V3 are reciprocal changes
  120. 120. Found in 1/3 of patients with inferior MI, Increased morbidity and mortality ST elevation in V4-V6 of Right-sided ECG
  121. 121. LVH, AV junctional rhythm, bradycardia
  122. 122. S1, QIII, TIII in 10-15%; T-wave inversions, especially occurring in inferior and anteroseptal simultaneously; RAD
  123. 123. 2004 Anna Story 152
  124. 124.  Twelve Lead Electrocardiography for ACLS Providers, D. Bruce Foster, D.O. W.B. Saunders Company  Rapid Interpretation of EKG’s , Dale Dubin, M.D., Cover Publishing Co. 1998  ECG’s Made Easy, Barbara Aehlert, RN, Mosby, 1995  The 12 Lead ECG in Acute Myocardial Infarction, Tim Phalen, Mosby, 1996  Color Coding EKG’s , Tim Carrick, RN, H &H Publishing, 1994  www.ecglibrary.com/ecghome.html  www.urbanhealth.udmercy.edu/ekg/read.html  www.ecglibrary.com/ecghome.html  www.nyerrn.com/h/ekg.htm

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