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EKG Basics

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Title: EKG Basics


1
EKG Basics 2
  • That Squigglely Line -
  • What Does It Really Mean ?
  • Part 2
  • David Arnall, Ph.D., P.T. (2000)

2
The V Leads
  • The Precordial Chest Leads Record The Hearts
    Electrical Activity In The Transverse Or
    Horizontal Plane.

3
http//www.publicsafetynet.net/12lead_dx.htmelect
rode
4
  • To Create The Six Precordial Chest Leads, Each
    Chest Lead Is Made Positive The Whole Body Is
    Considered Negative.

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
  • V3 Is Placed In Between V2 And V4.
  • V4 Is Placed In The Fifth Intercostal Space In
    The Midclavicular Line Near The Nipple.

7
  • V5 Is Placed In Between V4 And V6.
  • V6 Is Placed In The Fifth Intercostal Space In
    The Midaxillary Line.

8
http//endeavor.med.nyu.edu/courses/physiology/cou
rseware/ekg_pt1/EKGprecordial.html
9
  • When placing the precordial chest leads across
    the thorax, the clinician places the electrodes
    under the pectoralis major not over the breasts.

10
  • In The Chest Cavity, The Heart Is Positioned With
    The Right Ventricle Lying Anteriorly Medially
    While The Left Ventricle Lies Anterolaterally
    Posteriorly

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
  • Leads V3 V4 Lie Directly Over The
    Interventricular Septum. Their Line Of Sight Is
    To View The Electrical Activity Of The
    Interventricular Septum.

13
http//endeavor.med.nyu.edu/courses/physiology/cou
rseware/ekg_pt1/EKGprecolead.html
14
  • Leads V5 V6 Lie Over The Left Ventricle.
    Therefore, These Leads View The Electrical
    Activity Of The Left Ventricle.

15
  • The Precordial Chest Leads Can Be Divided Up Into
    Areas Of The Heart They View.

16
  • Leads V1, V2, V3, V4 Are The Anterior Leads.

17
  • Leads V5 V6 Look At The Left Lateral Wall.

18
In Review
  • Anterior Chest Leads
  • V1, V2, V3 V4

19
  • Left Lateral Wall Leads
  • aVL, Lead I , V5 V6

20
  • Inferior Chest Leads
  • Lead II, Lead III, Lead aVF

21
  • No Mans Land
  • aVR

22
  • A Review Of The Waves
  • Intervals Of The EKG

23
(No Transcript)
24
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.

25
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.

26
http//www.ovcnet.uoguelph.ca/ClinStudies/Courses/
Public/Cardiology/Concepts/ECGConcepts13-16.htm
27
  • Amplitude
  • A Normal Amplitude For A
  • P Wave Is 2-3 mm.

28
  • The P Wave Should Always Be Gently Rounded -
    Never Pointed Or Peaked.

29
  • Abnormal Amplitude Of The P Wave Is Often Seen In
    Cor Pulmonale, A-V Valve Disease, Hypertension
    In Patients With Congenital Heart Disease

30
  • P Waves Within The Same Lead That Are Multiformic
    Indicate The Presence Of More Than One Pacemaker
    In The Right Atrium.

31
  • In The Six Limb Leads, You Will Generally See P
    Waves In The Upright Position Except In aVR V1
    Where They Are Negatively Deflected.

32
http//bioscience.org/images/normalh.gif
33
  • You Will Frequently See Biphasic P Waves In Lead
    III, Lead V2 Occasionally In Lead aVL.

34
BiPhasic P Wave In V1
35
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.

36
  • The PR Interval Is A Time Lag And Represents The
    Period During Which There Is AV Nodal Capture Of
    The SA Node Signal.

37
  • The PR Interval Allows The Atria To Contract
    (atrial systole) Which Tops Off The Ventricles
    With Blood - An Event Called Atrial Kick.

38
  • 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.

39
(No Transcript)
40
http//doyle.ibme.utoronto.ca/EKG/rhythm/EKGTUTORI
AL.htm
41
  • The PR Interval Represents The Time Period
    Encompassing Atrial Depolarization Up To But Not
    Including The Start Of Ventricular
    Depolarization.

42
  • 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.
  • Marriotts Practical Electrocardiography, 9th
    ed., Galen S. Wagner, pg 39, 1994

43
  • 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)

44
  • If The PR Interval Is Longer Than 5 mm, It Is
    Called A Prolonged PR Interval May Indicate The
    Presence Of An AV Block.

45
First Degree AV Block
46
  • The PR Interval Shortens During Exercise Because
    Of The Sympathetic Tone That Predominates Over
    The Heart.

47
  • 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.

48
  • In Young Children, The PR Interval Is Shorter
    Than In Adults. The Childs Heart Rate Is Also
    Faster.

49
  • In A 1 Year Old Child At Rest, The Normal P-R
    Interval Is Typically .11 sec. Or Slightly Under
    3 mm.

50
  • For Children Who Are 6 Years Of Age, The P-R
    Interval At Rest Is .13 Seconds Or Slightly Over
    3 mm.

51
  • In Children 12 Years Of Age, The P-R Interval At
    Rest Will Be .14 Seconds Or About 3.5 mm.

52
  • In Grown Adults 18 Years Of Age And Older, The
    P-R Interval At Rest Will Be 3-5 mm In Length.

53
  • Prolonged P-R Intervals Are Symptomatic Of AV
    Blocks Due To Coronary Disease Rheumatic Fever.

54
  • 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.

55
  • Pathologies Resulting In PR Interval Shortening

56
  • Shortened P-R Intervals Are Seen In Patients With
    Pheochromocytoma And Wolfe-Parkinson-White
    Syndrome

57
  • 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.

58
  • 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.

59
  • 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.

60
  • W-P-W occurs in .15 - .20 of the population
    or 21,000 people. Patients with W-P-W are
    otherwise healthy.

61
  • 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.

62
  • Patients with W-P-W often complain of episodic
    symptoms that include chest discomfort,
    dizziness, and palpitations.

63
http//homepages.enterprise.net/djenkins/ecghome.h
tml
64
http//www.heartinfo.org/physician/ecg/wpw.htm
65
The Q Wave
  • Definition The Q Wave Is The First Downward
    Deflection After The P Wave Before The R Wave.

66
  • Sometimes Q Waves Are Present Sometimes They
    Are Absent Depending On The Lead.

67
  • It is common to normally see Q waves in leads I,
    II, aVL and in V4-6.

68
  • A Normal Q Wave Is Not Wider In Duration Than 0.5
    mm Or About .02 Seconds. Its Normal Amplitude Is

69
  • Q Waves Are An Indication Of Ventricular Septal
    Wall Depolarization.

70
  • 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.

71
  • Q Waves Of Normal Size Have No Diagnostic Meaning
    In Normal Hearts Except That The Septum Has
    Depolarized.

72
Significant Q Waves
  • Q waves In Leads I, II, aVF, aVL Can Mean
    Something If ...

73
  • 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.

74
  • Q waves of any size are normal in leads aVR.

75
  • 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.

76
  • 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.

77
  • 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.

78
  • 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.

79
  • 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.

80
The R Wave
  • Definition The R Wave Is The First Upward
    Deflection After The P Wave.

81
  • 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

82
http//www.heartinfo.org/physician/ecg/norm.htm
83
  • 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.

84
  • Loss of the R wave progression is abnormal and
    signals the possible presence of bundle branch
    blocks or the occurrence of a myocardial
    infarction.

85
The S Wave
  • Definition The S Wave Is Defined As The First
    Downward Deflection After The R Wave.

86
  • There is a normal progressive decrease in the
    size of the S wave in the precordial leads.

87
  • V1 through V2 should have large S waves with a
    decreasing appearance of S through V5 and V6.

88
http//www.heartinfo.org/physician/ecg/norm.htm
89
QRS Complex Generalities
  • Mostly Upward Deflected QRS Complexes Are Found
    In Leads I, II, III, aVF, aVL, V4, V5, and V6.

90
  • Mostly Downward Deflected QRS Complexes Will Be
    Seen In Leads aVR And V1,V2, And Sometimes V3.

91
  • The QRS Complex Signals The Depolarization Of The
    Ventricles.

92
  • A Normal QRS Complex Has A Duration of .06 -
    .12 Sec. Or About 1.5 - 3.0 mm.

93
  • If The QRS Is 3mm, The Medical Staff Will
    Construe It To Mean There Is An Abnormal
    Intraventricular Conduction Pathway.

94
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.

95
  • It Symbolizes The End Of Ventricular
    Depolarization To The Start Of Ventricular
    Repolarization.

96
  • It Is During This Phase Of The EKG When The Heart
    Is Being Passively Perfused - The Windkessel
    Effect.

97
  • The ST Segment Slopes Gently Up Toward The
    Isoelectric Line From The J Point And Ends At The
    Beginning Of The T Wave.

98
The ST Segment
99
Normal EKG w/ J Point In aVL
100
  • Normal Up Sloping Of The ST Segment May Be 1-2 mm
    In Indo-Europeans And As Much As 4 mm In
    African-Americans

101
  • The Normal Duration Of The ST Segment Is About
    2-3 mm.

102
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.

103
ST Segment Elevation
104
ST Segment Elevation
105
  • So...., The Classic Signs Of An Acute MI In
    Progress Are
  • Elevated ST Segment
  • Inverted T Wave
  • Presence Of A Q Wave

106
  • Signs Of An
  • Anterior Wall Infarction

107
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

108
ST Segment ChangesWith 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)

109
Acute Anterior Myocardial Infarctionhttp//homepa
ges.enterprise.net/djenkins/ami.html
110
  • In An Uncomplicated MI, These EKG Changes Will
    Largely Disappear Once The Infarction Has Frankly
    Resolved - Usually In About 3 Or More Days.

111
Mature Anterior Wall MI
112
  • Signs Of An
  • Inferior Wall Infarction

113
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

114
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.

115
Acute Inferior Myocardial Infarctionhttp//homepa
ges.enterprise.net/djenkins/ami.html
116
  • In An Uncomplicated MI, These EKG Changes Will
    Largely Disappear Once The Infarction Has Frankly
    Resolved - Usually In About 3 Days.

117
A Mature Inferior Wall MI
118
Old Inferior Wall MI
119
  • Signs Of A
  • Lateral Wall Infarction

120
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.

121
  • ST segment elevations will be seen in the lateral
    chest leads - Leads I, aVL and V5 and V6.

122
Acute Lateral Wall MI
123
  • In An Uncomplicated MI, These EKG Changes Will
    Largely Disappear Once The Infarction Has Frankly
    Resolved - Usually In About 3 Days.

124
Mature Lateral Wall Infarct
125
  • For All Types Of MIs, The Q Wave Often Remains
    As The Only Residual Sign That An Infarction Has
    Occurred. Also, The ST Segment May Be
    Permanently Depressed.

126
ST Segment Depression
  • When The ST Segment Is Depressed, Then It Is
    Usually A Sign Of Cardiac Ischemia.

127
ST Segment Depression
128
Types Of ST Segment Depression
129
  • ST Segment Depression May Be A Permanent Part Of
    The EKG Tracing.

130
  • At Rest The Patient May Have A Normal ST Segment.
    However, It May Become Depressed As The Persons
    Exercise Level Is Increased Above The Hearts
    Ability To Receive Adequate Perfusion.

131
  • 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.

132
  • 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.

133
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.

134
  • In Normal Hearts, The T Wave Is Usually Upright
    In Leads I, II, III, aVF, aVL, V2-V6.

135
  • In Normal Hearts, The T Wave Will Usually Be
    Upside Down In aVR And V1.

136
  • The Normal Duration Of The T Wave Is About 1-2 mm.

137
  • Normal Amplitude For The T Wave Is Highly
    Variable.

138
  • T Waves Get Taller During GXTs And Exercise.

139
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.

140
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.

141
  • The QT Interval Represents 40 Of The Normal
    Cardiac Cycle Whether At Rest Or During Exercise.

142
  • The QT Interval Becomes Shorter As The Heart
    Rate Increases.

143
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

144
  • Q Waves
  • Normal Duration
  • Normal Amplitude mm

145
  • QRS Complex
  • Normal Duration
  • Normal Amplitude Variable
  • ST Segment
  • Normal Amplitude 1-2 mm
  • Normal Duration 2-3 mm

146
  • T Wave
  • Normal Duration 2 mm
  • Normal Amplitude in Precordial Leads
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