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  1. 1. EKG Basics # 2 That Squigglely Line - What Does It Really Mean ? Part # 2 David Arnall, Ph.D., P.T. (2000)
  2. 2. The V Leads  The Precordial Chest Leads Record The Heart’s Electrical Activity In The Transverse Or Horizontal Plane.
  3. 3. http://www.publicsafetynet.net/12lead_dx.htm#electrode
  4. 4.  To Create The Six Precordial Chest Leads, Each Chest Lead Is Made Positive & The Whole Body Is Considered Negative.
  5. 5. Lead Positioning  V1 Is Placed In The Fourth Intercostal Space To The Right Of The Sternum.  V2 Is Placed In The Fourth Intercostal Space To The Left Of The Sternum.
  6. 6.  V3 Is Placed In Between V2 And V4.  V4 Is Placed In The Fifth Intercostal Space In The Midclavicular Line Near The Nipple.
  7. 7.  V5 Is Placed In Between V4 And V6.  V6 Is Placed In The Fifth Intercostal Space In The Midaxillary Line.
  8. 8. http://endeavor.med.nyu.edu/courses/physiology/courseware/ekg _pt1/EKGprecordial.html
  9. 9.  When placing the precordial chest leads across the thorax, the clinician places the electrodes under the pectoralis major & not over the breasts.
  10. 10.  In The Chest Cavity, The Heart Is Positioned With The Right Ventricle Lying Anteriorly & Medially While The Left Ventricle Lies Anterolaterally & Posteriorly
  11. 11.  Therefore, Leads V1 & V2 Lie Directly Over The Right Ventricle. Their Line Of Sight Is To View The Electrical Activity Coming From The Right Ventricle.
  12. 12.  Leads V3 & V4 Lie Directly Over The Interventricular Septum. Their Line Of Sight Is To View The Electrical Activity Of The Interventricular Septum.
  13. 13. http://endeavor.med.nyu.edu/courses/physiology/courseware/ekg _pt1/EKGprecolead.html
  14. 14.  Leads V5 & V6 Lie Over The Left Ventricle. Therefore, These Leads View The Electrical Activity Of The Left Ventricle.
  15. 15.  The Precordial Chest Leads Can Be Divided Up Into Areas Of The Heart They View.
  16. 16.  Leads V1, V2, V3, & V4 Are The Anterior Leads.
  17. 17.  Leads V5 & V6 Look At The Left Lateral Wall.
  18. 18. In Review Anterior Chest Leads V1, V2, V3 & V4
  19. 19. Left Lateral Wall Leads aVL, Lead I , V5 & V6
  20. 20. Inferior Chest Leads Lead II, Lead III, & Lead aVF
  21. 21. No Man’s Land aVR
  22. 22. A Review Of The Waves & Intervals Of The EKG
  23. 23. The P Wave  The P Wave Is The Signal That Electrical Potential Has Left The SA Node, Swept Across The Atria, & Has Initiated Atrial Contraction.
  24. 24. What Is A Normal P Wave ?  Duration : The Normal Duration Of A P Wave is 2.0 - 2.5 mm (.04 - .1 sec)  If It Is Greater Than 2.75 mm (.11 sec) It Is Considered To Be An Abnormal P Wave.
  25. 25. http://www.ovcnet.uoguelph.ca/ClinStudies/Courses/Public/Card iology/Concepts/ECGConcepts13-16.htm
  26. 26. Amplitude A Normal Amplitude For A P Wave Is 2-3 mm.
  27. 27. The P Wave Should Always Be Gently Rounded - Never Pointed Or Peaked.
  28. 28.  Abnormal Amplitude Of The P Wave Is Often Seen In Cor Pulmonale, A-V Valve Disease, Hypertension & In Patients With Congenital Heart Disease
  29. 29.  P Waves Within The Same Lead That Are Multiformic Indicate The Presence Of More Than One Pacemaker In The Right Atrium.
  30. 30.  In The Six Limb Leads, You Will Generally See P Waves In The Upright Position Except In aVR & V1 Where They Are Negatively Deflected.
  31. 31. http://bioscience.org/images/normalh.gif
  32. 32.  You Will Frequently See Biphasic P Waves In Lead III, Lead V2 & Occasionally In Lead aVL.
  33. 33. BiPhasic P Wave In V1
  34. 34. The PR Interval  After The P Wave There Is A “Silent Period” Where Nothing Is Happening In The EKG Tracing. This Quiescent Period Is Called The PR Interval.
  35. 35.  The PR Interval Is A Time Lag And Represents The Period During Which There Is AV Nodal Capture Of The SA Node Signal.
  36. 36.  The PR Interval Allows The Atria To Contract (atrial systole) Which “Tops Off” The Ventricles With Blood - An Event Called Atrial Kick.
  37. 37.  The PR Interval Is Measured From The Beginning Of The P Wave To The Beginning Of The Q Wave Or The Beginning Of The R Wave If The Q Wave Is Absent.
  38. 38. http://doyle.ibme.utoronto.ca/EKG/rhythm/EKGTUTORIAL.htm
  39. 39.  The PR Interval Represents The Time Period Encompassing Atrial Depolarization Up To But Not Including The Start Of Ventricular Depolarization.
  40. 40.  “A major portion of the PR interval reflects the slow conduction through the AV node which is controlled by the sympathetic-parasympathetic balance within the autonomic nervous system”. Marriott’s Practical Electrocardiography, 9th ed., Galen S. Wagner, pg 39, 1994
  41. 41.  Duration : The Adult PR Interval Is Normally Between 3-5 mm Or .12 - .20 Seconds In Duration. Some Cardiologists Will Say It Is Normal Out To .22 Seconds (5 1/2 mm)
  42. 42.  If The PR Interval Is Longer Than 5 mm, It Is Called A Prolonged PR Interval & May Indicate The Presence Of An AV Block.
  43. 43. First Degree AV Block
  44. 44.  The PR Interval Shortens During Exercise Because Of The Sympathetic Tone That Predominates Over The Heart.
  45. 45.  If The PR Interval Could Not Shorten, Along With Other Segments In The EKG, Then Acceleration Of Heart Rate During Exercise Would Be Difficult If Not Impossible.
  46. 46.  In Young Children, The PR Interval Is Shorter Than In Adults. The Child’s Heart Rate Is Also Faster.
  47. 47.  In A 1 Year Old Child At Rest, The Normal P-R Interval Is Typically .11 sec. Or Slightly Under 3 mm.
  48. 48.  For Children Who Are 6 Years Of Age, The P-R Interval At Rest Is .13 Seconds Or Slightly Over 3 mm.
  49. 49.  In Children 12 Years Of Age, The P-R Interval At Rest Will Be .14 Seconds Or About 3.5 mm.
  50. 50.  In Grown Adults 18 Years Of Age And Older, The P-R Interval At Rest Will Be 3-5 mm In Length.
  51. 51.  Prolonged P-R Intervals Are Symptomatic Of : AV Blocks Due To Coronary Disease & Rheumatic Fever.
  52. 52.  Sometimes, Prolonged P-R Intervals Not Related To Heart Disease, Can Be Seen In Healthy Athletes - An Aberration Called A Normal Variant. This Can Be Seen In About ~ 1% - 2% Of The Healthy, Young Population.
  53. 53. Pathologies Resulting In PR Interval Shortening
  54. 54.  Shortened P-R Intervals Are Seen In Patients With Pheochromocytoma And Wolfe-Parkinson-White Syndrome
  55. 55.  Pheochromocytoma is a tumor in the adrenal medulla that results in a greater-than-normal release of catecholamines. The high blood concentration of catecholamines causes the heart rate to accelerate.
  56. 56.  Wolff-Parkinson-White Syndrome is a medical condition in which atrioventricular myocardial accessory pathways electrically pre-excite the ventricles to contract producing an extremely short PR interval.
  57. 57.  These accessory electrical pathways are remnants of fetal pathways that did not disappear after birth. The Bundle Of Kent has been implicated as a common aberrant pathway in W-P-W.
  58. 58.  W-P-W occurs in ~ .15% - .20% of the population or 2:1,000 people. Patients with W-P-W are otherwise healthy.
  59. 59.  W-P-W effects men more than women and can evolve into atrial and ventricular dysrhythmias with a general mortality up to 4% of the effected population.
  60. 60.  Patients with W-P-W often complain of episodic symptoms that include chest discomfort, dizziness, and palpitations.
  61. 61. http://homepages.enterprise.net/djenkins/ecghome.html
  62. 62. http://www.heartinfo.org/physician/ecg/wpw.htm
  63. 63. The Q Wave  Definition : The Q Wave Is The First Downward Deflection After The P Wave & Before The R Wave.
  64. 64.  Sometimes Q Waves Are Present & Sometimes They Are Absent Depending On The Lead.
  65. 65.  It is common to normally see Q waves in leads I, II, aVL and in V4-6.
  66. 66.  A Normal Q Wave Is Not Wider In Duration Than 0.5 mm Or About .02 Seconds. Its Normal Amplitude Is < 1 mm.
  67. 67.  Q Waves Are An Indication Of Ventricular Septal Wall Depolarization.
  68. 68.  They Appear Before The QRS Complex Because The Fascicle That Conducts The Signal Is Higher Than The Right And Left Bundle Branch That Give You The QRS Complex.
  69. 69.  Q Waves Of Normal Size Have No Diagnostic Meaning In Normal Hearts Except That The Septum Has Depolarized.
  70. 70. Significant Q Waves  Q waves In Leads I, II, aVF, & aVL Can Mean Something If ...
  71. 71. 1. They Are Between 25% - 33% Of The Amplitude Of The R Wave. 2. They Are Greater Than 0.04 Seconds (1 mm) In Duration.
  72. 72.  Q waves of any size are normal in leads aVR.
  73. 73.  If They Are 25%-33% Of The Total Amplitude Of The R Wave, Then They Are Significant For The Presence Of An MI In The Lead Where The Q Wave Appears.
  74. 74.  In Other Words, If The Significant Q Wave Appears In Leads II, III Or aVF, Then The MI Must Have Occurred In The Inferior Portion Of The Heart - The Right Coronary Is Blocked.
  75. 75.  If The Significant Q Wave Appeared In Lead I Or aVL, Then The MI Must Have Occurred In The Antero-Lateral Or Lateral Portions Of The Left Ventricle.
  76. 76.  Since Lead I & aVL Cover The Lateral Wall Of The Left Ventricle, Then The Occlusion Likely Occurred In The Circumflex Or The Marginal Branches Of The Left Coronary.
  77. 77.  Use The Precordial Chest Leads To Look For Significant Q Waves For The Presence Of An MI In The Anterior Portion Of The Heart - V1 - V6 - The LAD Is Occluded.
  78. 78. The R Wave  Definition : The R Wave Is The First Upward Deflection After The P Wave.
  79. 79.  In the precordial chest leads, there should be an R wave progression - i.e. - an ever increasing amplitude of the R wave from V1 through V6
  80. 80. http://www.heartinfo.org/physician/ecg/norm.htm
  81. 81.  R wave progression occurs because the precordial chest leads sweep across the thoracic cage looking from the thinner right ventricle across to the thicker left ventricle.
  82. 82.  Loss of the R wave progression is abnormal and signals the possible presence of bundle branch blocks or the occurrence of a myocardial infarction.
  83. 83. The S Wave  Definition : The S Wave Is Defined As The First Downward Deflection After The R Wave.
  84. 84.  There is a normal progressive decrease in the size of the S wave in the precordial leads.
  85. 85.  V1 through V2 should have large S waves with a decreasing appearance of S through V5 and V6.
  86. 86. http://www.heartinfo.org/physician/ecg/norm.htm
  87. 87. QRS Complex Generalities  Mostly Upward Deflected QRS Complexes Are Found In Leads I, II, III, aVF, aVL, V4, V5, and V6.
  88. 88.  Mostly Downward Deflected QRS Complexes Will Be Seen In Leads aVR And V1,V2, And Sometimes V3.
  89. 89.  The QRS Complex Signals The Depolarization Of The Ventricles.
  90. 90.  A Normal QRS Complex Has A Duration of ~ .06 - .12 Sec. Or About 1.5 - 3.0 mm.
  91. 91.  If The QRS Is >3mm, The Medical Staff Will Construe It To Mean There Is An Abnormal Intraventricular Conduction Pathway.
  92. 92. The ST Segment  The ST Segment Is The Pause After The QRS Complex - The Interval Between The End Of The QRS Complex & The Beginning Of The T Wave.
  93. 93.  It Symbolizes The End Of Ventricular Depolarization To The Start Of Ventricular Repolarization.
  94. 94.  It Is During This Phase Of The EKG When The Heart Is Being Passively Perfused - The Windkessel Effect.
  95. 95.  The ST Segment Slopes Gently Up Toward The Isoelectric Line From The J Point And Ends At The Beginning Of The T Wave.
  96. 96. The ST Segment
  97. 97. Normal EKG w/ J Point In aVL
  98. 98.  Normal Up Sloping Of The ST Segment May Be 1-2 mm In Indo- Europeans And As Much As 4 mm In African-Americans
  99. 99.  The Normal Duration Of The ST Segment Is About 2-3 mm.
  100. 100. ST Segment Elevation  When The ST Segment Is Elevated In A Patient With Known Disease, It Is Usually A Sign Of An Evolving Transmural Infarction - An MI In Progress.
  101. 101. ST Segment Elevation
  102. 102. ST Segment Elevation
  103. 103.  So...., The Classic Signs Of An Acute MI In Progress Are : –Elevated ST Segment –Inverted T Wave –Presence Of A Q Wave
  104. 104. Signs Of An Anterior Wall Infarction
  105. 105. Anterior Wall Infarction  An anterior wall MI is usually caused by an occlusion of the LAD  EKG changes are seen in any of the precordial chest leads - V1 - V6
  106. 106. ST Segment Changes With An Acute Anterior MI  ST segment elevation in V1-V6 and in Leads I and aVL (the lateral wall leads).  Reciprocal ST segment depression in Leads II, III & aVF (the inferior leads)
  107. 107. Acute Anterior Myocardial Infarction http://homepages.enterprise.net/djenkins/ami.html
  108. 108.  In An Uncomplicated MI, These EKG Changes Will Largely Disappear Once The Infarction Has Frankly Resolved - Usually In About 3 Or More Days.
  109. 109. Mature Anterior Wall MI
  110. 110. Signs Of An Inferior Wall Infarction
  111. 111. Inferior Wall Infarction  This infarction occurs on the diaphragmatic surface of the heart.  It is frequently caused by an occlusion to blood flow through the right coronary
  112. 112. ST Segment Changes With An Acute Inferior MI  ST segment elevations in Leads II, III and aVF  Reciprocal ST segment changes in Leads I, aVL, V1-V6.
  113. 113. Acute Inferior Myocardial Infarction http://homepages.enterprise.net/djenkins/ami.html
  114. 114.  In An Uncomplicated MI, These EKG Changes Will Largely Disappear Once The Infarction Has Frankly Resolved - Usually In About 3 Days.
  115. 115. A Mature Inferior Wall MI
  116. 116. Old Inferior Wall MI
  117. 117. Signs Of A Lateral Wall Infarction
  118. 118. Lateral Wall Infarction  This type of MI involves the lateral wall of the heart - the left ventricle.  It is often caused by an occlusion to blood flow through the circumflex artery.
  119. 119.  ST segment elevations will be seen in the lateral chest leads - Leads I, aVL and V5 and V6.
  120. 120. Acute Lateral Wall MI
  121. 121.  In An Uncomplicated MI, These EKG Changes Will Largely Disappear Once The Infarction Has Frankly Resolved - Usually In About 3 Days.
  122. 122. Mature Lateral Wall Infarct
  123. 123.  For All Types Of MI’s, The Q Wave Often Remains As The Only Residual Sign That An Infarction Has Occurred. Also, The ST Segment May Be Permanently Depressed.
  124. 124. ST Segment Depression  When The ST Segment Is Depressed, Then It Is Usually A Sign Of Cardiac Ischemia.
  125. 125. ST Segment Depression
  126. 126. Types Of ST Segment Depression
  127. 127.  ST Segment Depression May Be A Permanent Part Of The EKG Tracing.
  128. 128.  At Rest The Patient May Have A Normal ST Segment. However, It May Become Depressed As The Person’s Exercise Level Is Increased Above The Heart’s Ability To Receive Adequate Perfusion.
  129. 129.  The ST segment depression will begin to appear as the heart becomes ischemic  It will continue to be more depressed the more ischemic the heart becomes.
  130. 130.  The ST segment will normalize once the exercise intensity is reduced to a level in which the heart receives enough perfusion to support the work that is being demanded.
  131. 131. The T Wave  The T Wave Represents Repolarization Of The Ventricles.  Repolarization Proceeds From The Apex Of The Heart To The Base Of The Heart.
  132. 132.  In Normal Hearts, The T Wave Is Usually Upright In Leads I, II, III, aVF, aVL, & V2-V6.
  133. 133.  In Normal Hearts, The T Wave Will Usually Be Upside Down In aVR And V1.
  134. 134.  The Normal Duration Of The T Wave Is About 1-2 mm.
  135. 135.  Normal Amplitude For The T Wave Is Highly Variable.
  136. 136.  T Waves Get Taller During GXT’s And Exercise.
  137. 137. T Waves During Infarction  With infarction, the T wave usually becomes tall and narrow - referred to as “peaking”.  With time and the onset of ischemia, the T wave will invert.
  138. 138. The QT Interval  The QT Interval Encompasses The Time From The Beginning Of The Q Or R Wave Through The End Of The T Wave.
  139. 139.  The QT Interval Represents 40% Of The Normal Cardiac Cycle Whether At Rest Or During Exercise.
  140. 140.  The QT Interval Becomes Shorter As The Heart Rate Increases.
  141. 141. Summary Of Durations & Amplitudes Of The P-QRS-T  P Waves Normal Duration : 2.5 mm Normal Amplitude : 2-3 mm  PR Intervals Normal Duration : 3-5 mm
  142. 142.  Q Waves Normal Duration : < .5 mm Normal Amplitude : <25% of R amplitude or ~ 1.0 mm
  143. 143.  QRS Complex Normal Duration : < 3.0 mm Normal Amplitude : Variable  ST Segment Normal Amplitude : 1-2 mm Normal Duration : 2-3 mm
  144. 144.  T Wave Normal Duration : 2 mm Normal Amplitude : < 5 mm in Limb Leads & < 10 mm in Precordial Leads