EKG Basics # 2EKG Basics # 2

That Squigglely Line -That Squigglely Line -

What Does It Really What Does It Really Mean ?Mean ?

Part # 2Part # 2

David Arnall, Ph.D., P.T. (2000)David Arnall, Ph.D., P.T. (2000)

The V LeadsThe V Leads

The Precordial Chest The Precordial Chest Leads Record The Leads Record The Heart’s Electrical Heart’s Electrical Activity In The Activity In The Transverse Or Transverse Or Horizontal Plane.Horizontal Plane.

http://www.publicsafetynet.net/http://www.publicsafetynet.net/12lead_dx.htm#electrode12lead_dx.htm#electrode

To Create The Six To Create The Six Precordial Chest Leads, Precordial Chest Leads, Each Chest Lead Is Made Each Chest Lead Is Made Positive & The Whole Positive & The Whole Body Is Considered Body Is Considered Negative.Negative.

Lead PositioningLead Positioning

V1 Is Placed In The Fourth V1 Is Placed In The Fourth Intercostal Space To The Intercostal Space To The Right Of The Sternum.Right Of The Sternum.

V2 Is Placed In The Fourth V2 Is Placed In The Fourth Intercostal Space To The Intercostal Space To The Left Of The Sternum.Left Of The Sternum.

V3 Is Placed In Between V3 Is Placed In Between V2 And V4.V2 And V4.

V4 Is Placed In The Fifth V4 Is Placed In The Fifth Intercostal Space In The Intercostal Space In The Midclavicular Line Near Midclavicular Line Near The Nipple.The Nipple.

V5 Is Placed In Between V5 Is Placed In Between V4 And V6.V4 And V6.

V6 Is Placed In The Fifth V6 Is Placed In The Fifth Intercostal Space In The Intercostal Space In The Midaxillary Line.Midaxillary Line.

http://endeavor.med.nyu.edu/courses/physiology/http://endeavor.med.nyu.edu/courses/physiology/courseware/ekg_pt1/EKGprecordial.htmlcourseware/ekg_pt1/EKGprecordial.html

When placing the When placing the precordial chest leads precordial chest leads across the thorax, the across the thorax, the clinician places the clinician places the electrodes under the electrodes under the pectoralis major & not pectoralis major & not over the breasts.over the breasts.

In The Chest Cavity, The In The Chest Cavity, The Heart Is Positioned With Heart Is Positioned With The Right Ventricle Lying The Right Ventricle Lying Anteriorly & Medially Anteriorly & Medially While The Left Ventricle While The Left Ventricle Lies Anterolaterally & Lies Anterolaterally & PosteriorlyPosteriorly

Therefore, Leads V1 & V2 Therefore, Leads V1 & V2 Lie Directly Over The Lie Directly Over The Right Ventricle. Their Right Ventricle. Their Line Of Sight Is To View Line Of Sight Is To View The Electrical Activity The Electrical Activity Coming From The Right Coming From The Right Ventricle.Ventricle.

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

http://endeavor.med.nyu.edu/courses/physiology/http://endeavor.med.nyu.edu/courses/physiology/courseware/ekg_pt1/EKGprecolead.htmlcourseware/ekg_pt1/EKGprecolead.html

Leads V5 & V6 Lie Over Leads V5 & V6 Lie Over The Left Ventricle. The Left Ventricle. Therefore, These Leads Therefore, These Leads View The Electrical View The Electrical Activity Of The Left Activity Of The Left Ventricle.Ventricle.

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

Leads V1, V2, V3, & V4 Leads V1, V2, V3, & V4 Are The Anterior Leads.Are The Anterior Leads.

Leads V5 & V6 Look At Leads V5 & V6 Look At The Left Lateral Wall.The Left Lateral Wall.

In ReviewIn Review

Anterior Chest LeadsAnterior Chest Leads

V1, V2, V3 & V4V1, V2, V3 & V4

Left Lateral Wall LeadsLeft Lateral Wall Leads

aVL, Lead I , V5 & V6aVL, Lead I , V5 & V6

Inferior Chest LeadsInferior Chest Leads

Lead II, Lead III, & Lead Lead II, Lead III, & Lead aVFaVF

No Man’s Land No Man’s Land

aVRaVR

A Review Of The WavesA Review Of The Waves

& Intervals Of The EKG& Intervals Of The EKG

The P WaveThe P Wave

The P Wave Is The Signal The P Wave Is The Signal That Electrical Potential That Electrical Potential Has Left The SA Node, Has Left The SA Node, Swept Across The Atria, Swept Across The Atria, & Has Initiated Atrial & Has Initiated Atrial Contraction.Contraction.

What Is A Normal P What Is A Normal P Wave ?Wave ?

Duration : The Normal Duration : The Normal Duration Of A P Wave is Duration Of A P Wave is 2.0 - 2.5 mm (.04 - .1 sec)2.0 - 2.5 mm (.04 - .1 sec)

If It Is Greater Than 2.75 If It Is Greater Than 2.75 mm (.11 sec) It Is mm (.11 sec) It Is Considered To Be An Considered To Be An Abnormal P Wave.Abnormal P Wave.

http://www.ovcnet.uoguelph.ca/ClinStudies/http://www.ovcnet.uoguelph.ca/ClinStudies/Courses/Public/Cardiology/Concepts/Courses/Public/Cardiology/Concepts/

ECGConcepts13-16.htmECGConcepts13-16.htm

Amplitude Amplitude

A Normal Amplitude For A Normal Amplitude For AA

P Wave Is 2-3 mm.P Wave Is 2-3 mm.

The P Wave Should The P Wave Should Always Be Gently Always Be Gently

Rounded - Never Pointed Rounded - Never Pointed Or Peaked.Or Peaked.

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

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

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

http://bioscience.org/images/normalh.gifhttp://bioscience.org/images/normalh.gif

You Will Frequently See You Will Frequently See Biphasic P Waves In Biphasic P Waves In Lead III, Lead V2 & Lead III, Lead V2 & Occasionally In Lead Occasionally In Lead aVL.aVL.

BiPhasic P Wave In V1BiPhasic P Wave In V1

The PR IntervalThe PR Interval After The P Wave There Is After The P Wave There Is

A “Silent Period” Where A “Silent Period” Where Nothing Is Happening In Nothing Is Happening In The EKG Tracing. This The EKG Tracing. This Quiescent Period Is Called Quiescent Period Is Called The PR Interval.The PR Interval.

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

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

The PR Interval Is The PR Interval Is Measured From The Measured From The Beginning Of The P Wave Beginning Of The P Wave To The Beginning Of The Q To The Beginning Of The Q Wave Or The Beginning Of Wave Or The Beginning Of The R Wave If The Q Wave The R Wave If The Q Wave Is Absent.Is Absent.

http://doyle.ibme.utoronto.ca/EKG/rhythm/http://doyle.ibme.utoronto.ca/EKG/rhythm/EKGTUTORIAL.htmEKGTUTORIAL.htm

The PR Interval The PR Interval Represents The Time Represents The Time Period Encompassing Period Encompassing Atrial Depolarization Up To Atrial Depolarization Up To But But Not Including Not Including The The Start Of Ventricular Start Of Ventricular Depolarization.Depolarization.

““A major portion of the PR A major portion of the PR interval reflects the slow interval reflects the slow conduction through the AV conduction through the AV node which is controlled by node which is controlled by the sympathetic-the sympathetic-parasympathetic balance parasympathetic balance within the autonomic nervous within the autonomic nervous systemsystem”.”.

Marriott’s Practical Electrocardiography, 9th ed., Galen S. Wagner, pg Marriott’s Practical Electrocardiography, 9th ed., Galen S. Wagner, pg 39, 199439, 1994

DurationDuration : The Adult PR : The Adult PR Interval Is Normally Between Interval Is Normally Between 3-5 mm Or .12 - .20 Seconds 3-5 mm Or .12 - .20 Seconds In Duration. Some In Duration. Some Cardiologists Will Say It Is Cardiologists Will Say It Is Normal Out To .22 Seconds Normal Out To .22 Seconds (5 1/2 mm)(5 1/2 mm)

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

First Degree AV BlockFirst Degree AV Block

The PR Interval The PR Interval Shortens During Shortens During Exercise Because Of Exercise Because Of The Sympathetic Tone The Sympathetic Tone That Predominates That Predominates Over The Heart. Over The Heart.

If The PR Interval Could Not If The PR Interval Could Not Shorten,Shorten, Along With Other Along With Other Segments In The EKG, Then Segments In The EKG, Then Acceleration Of Heart Rate Acceleration Of Heart Rate During Exercise Would Be During Exercise Would Be Difficult If Not Impossible.Difficult If Not Impossible.

In Young Children, The PR In Young Children, The PR Interval Is Shorter Than In Interval Is Shorter Than In Adults. The Child’s Heart Adults. The Child’s Heart Rate Is Also Faster.Rate Is Also Faster.

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

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

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

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

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

Sometimes, Prolonged P-R Sometimes, Prolonged P-R Intervals Not Related To Intervals Not Related To Heart Disease, Can Be Seen Heart Disease, Can Be Seen In Healthy Athletes - An In Healthy Athletes - An Aberration Called A Aberration Called A Normal Normal VariantVariant. This Can Be Seen In . This Can Be Seen In About ~ 1% - 2% Of The About ~ 1% - 2% Of The Healthy, Young Population.Healthy, Young Population.

Pathologies Resulting In Pathologies Resulting In PR Interval ShorteningPR Interval Shortening

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

PheochromocytomaPheochromocytoma is a tumor is a tumor in the adrenal medulla that in the adrenal medulla that results in a greater-than-normal results in a greater-than-normal release of catecholamines. The release of catecholamines. The high blood concentration of high blood concentration of catecholamines causes the catecholamines causes the heart rate to accelerate.heart rate to accelerate.

Wolff-Parkinson-White Wolff-Parkinson-White SyndromeSyndrome is a medical is a medical condition in which condition in which atrioventricular myocardial atrioventricular myocardial accessory pathways electrically accessory pathways electrically pre-excite the ventricles to pre-excite the ventricles to contract producing an contract producing an extremely short PR interval.extremely short PR interval.

These accessory electrical These accessory electrical pathways are remnants of pathways are remnants of fetal pathways that did not fetal pathways that did not disappear after birth. The disappear after birth. The Bundle Of Kent has been Bundle Of Kent has been implicated as a common implicated as a common aberrant pathway in W-P-aberrant pathway in W-P-W.W.

W-P-W occurs in ~ .15% - W-P-W occurs in ~ .15% - .20% of the population .20% of the population or 2:1,000 people. or 2:1,000 people. Patients with W-P-W are Patients with W-P-W are otherwise healthy.otherwise healthy.

W-P-W effects men more W-P-W effects men more than women and can evolve than women and can evolve into atrial and ventricular into atrial and ventricular dysrhythmias with a dysrhythmias with a general mortality up to 4% general mortality up to 4% of the effected population.of the effected population.

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

http://homepages.enterprise.net/djenkins/ecghome.htmlhttp://homepages.enterprise.net/djenkins/ecghome.html

http://www.heartinfo.org/physician/ecg/wpw.htmhttp://www.heartinfo.org/physician/ecg/wpw.htm

The Q WaveThe Q Wave

DefinitionDefinition : The Q Wave Is : The Q Wave Is The First Downward The First Downward Deflection After The P Wave Deflection After The P Wave & Before The R Wave.& Before The R Wave.

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

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

A Normal Q Wave Is Not A Normal Q Wave Is Not Wider In Duration Than 0.5 Wider In Duration Than 0.5 mm Or About .02 Seconds. mm Or About .02 Seconds. Its Normal Amplitude Is Its Normal Amplitude Is << 1 1 mm.mm.

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

They Appear Before The They Appear Before The QRS Complex Because The QRS Complex Because The Fascicle That Conducts Fascicle That Conducts The Signal Is Higher Than The Signal Is Higher Than The Right And Left Bundle The Right And Left Bundle Branch That Give You The Branch That Give You The QRS Complex.QRS Complex.

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

Significant Q WavesSignificant Q Waves

Q waves In Leads I, II, Q waves In Leads I, II, aVF, & aVL aVF, & aVL CanCan Mean Mean Something If ...Something If ...

1. They Are Between 25% 1. They Are Between 25% - 33% Of The Amplitude - 33% Of The Amplitude Of The R Wave.Of The R Wave.

2. They Are Greater Than 2. They Are Greater Than 0.04 Seconds (1 mm) In 0.04 Seconds (1 mm) In Duration.Duration.

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

If They Are 25%-33% Of The If They Are 25%-33% Of The Total Amplitude Of The R Total Amplitude Of The R Wave, Then They Are Wave, Then They Are Significant For The Significant For The Presence Of An MI In The Presence Of An MI In The Lead Where The Q Wave Lead Where The Q Wave Appears.Appears.

In Other Words, If The In Other Words, If The Significant Q Wave Appears Significant Q Wave Appears In Leads II, III Or aVF, Then In Leads II, III Or aVF, Then The MI Must Have Occurred The MI Must Have Occurred In The Inferior Portion Of The In The Inferior Portion Of The Heart - The Right Coronary Is Heart - The Right Coronary Is Blocked.Blocked.

If The Significant Q Wave If The Significant Q Wave Appeared In Lead I Or aVL, Appeared In Lead I Or aVL, Then The MI Must Have Then The MI Must Have Occurred In The Antero-Occurred In The Antero-Lateral Or Lateral Portions Lateral Or Lateral Portions Of The Left Ventricle.Of The Left Ventricle.

Since Lead I & aVL Cover The Since Lead I & aVL Cover The Lateral Wall Of The Left Lateral Wall Of The Left Ventricle, Then The Ventricle, Then The Occlusion Likely Occurred In Occlusion Likely Occurred In The Circumflex Or The The Circumflex Or The Marginal Branches Of The Marginal Branches Of The Left Coronary.Left Coronary.

Use The Precordial Chest Use The Precordial Chest Leads To Look For Significant Leads To Look For Significant Q Waves For The Presence Of Q Waves For The Presence Of An MI In The Anterior Portion An MI In The Anterior Portion Of The Heart - V1 - V6 - The Of The Heart - V1 - V6 - The LAD Is Occluded.LAD Is Occluded.

The R WaveThe R Wave

DefinitionDefinition : The R Wave : The R Wave Is The First Upward Is The First Upward Deflection After The P Deflection After The P Wave.Wave.

In the precordial chest In the precordial chest leads, there should be leads, there should be an R wave progression - an R wave progression - i.e. - an ever increasing i.e. - an ever increasing amplitude of the R wave amplitude of the R wave from V1 through V6from V1 through V6

http://www.heartinfo.org/physician/ecg/norm.htmhttp://www.heartinfo.org/physician/ecg/norm.htm

R wave progression occurs R wave progression occurs because the precordial because the precordial chest leads sweep across chest leads sweep across the thoracic cage looking the thoracic cage looking from the thinner right from the thinner right ventricle across to the ventricle across to the thicker left ventricle.thicker left ventricle.

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

The S WaveThe S Wave

DefinitionDefinition : The S Wave Is : The S Wave Is Defined As The First Defined As The First Downward Deflection After Downward Deflection After The R Wave.The R Wave.

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

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

http://www.heartinfo.org/physician/ecg/norm.htmhttp://www.heartinfo.org/physician/ecg/norm.htm

QRS Complex GeneralitiesQRS Complex Generalities

Mostly Upward Deflected Mostly Upward Deflected QRS Complexes Are QRS Complexes Are Found In Leads I, II, III, Found In Leads I, II, III, aVF, aVL, V4, V5, and aVF, aVL, V4, V5, and V6.V6.

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

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

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

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

The ST SegmentThe ST Segment

The ST Segment Is The The ST Segment Is The Pause After The QRS Pause After The QRS Complex - The Interval Complex - The Interval Between The End Of The Between The End Of The QRS Complex & The QRS Complex & The Beginning Of The T Wave.Beginning Of The T Wave.

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

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

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

The ST SegmentThe ST Segment

Normal EKG w/ J Point In Normal EKG w/ J Point In aVLaVL

Normal Up Sloping Of The Normal Up Sloping Of The ST Segment May Be 1-2 mm ST Segment May Be 1-2 mm In Indo-Europeans And As In Indo-Europeans And As Much As 4 mm In African-Much As 4 mm In African-AmericansAmericans

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

ST Segment ElevationST Segment Elevation

When The ST Segment Is When The ST Segment Is Elevated In A Patient Elevated In A Patient With Known Disease, It Is With Known Disease, It Is Usually A Sign Of An Usually A Sign Of An Evolving Transmural Evolving Transmural Infarction - An MI In Infarction - An MI In Progress.Progress.

ST Segment ElevationST Segment Elevation

ST Segment ElevationST Segment Elevation

So...., The Classic Signs So...., The Classic Signs Of An Acute MI In Of An Acute MI In Progress Are :Progress Are :–Elevated ST SegmentElevated ST Segment–Inverted T WaveInverted T Wave–Presence Of A Q WavePresence Of A Q Wave

Signs Of An Signs Of An

Anterior Wall InfarctionAnterior Wall Infarction

Anterior Wall InfarctionAnterior Wall Infarction

An anterior wall MI is An anterior wall MI is usually caused by an usually caused by an occlusion of the LADocclusion of the LAD

EKG changes are seen in EKG changes are seen in any of the precordial chest any of the precordial chest leads - V1 - V6leads - V1 - V6

ST Segment ChangesST Segment ChangesWith An Acute Anterior With An Acute Anterior

MI MI ST segment elevation in ST segment elevation in

V1-V6 and in Leads I and V1-V6 and in Leads I and aVL (the lateral wall aVL (the lateral wall leads).leads).

Reciprocal ST segment Reciprocal ST segment depression in Leads II, III & depression in Leads II, III & aVF (the inferior leads)aVF (the inferior leads)

Acute Anterior Myocardial InfarctionAcute Anterior Myocardial Infarctionhttp://homepages.enterprise.net/djenkins/ami.htmlhttp://homepages.enterprise.net/djenkins/ami.html

In An Uncomplicated MI, In An Uncomplicated MI, These EKG Changes Will These EKG Changes Will Largely Disappear Once Largely Disappear Once The Infarction Has Frankly The Infarction Has Frankly Resolved - Usually In Resolved - Usually In About 3 Or More Days. About 3 Or More Days.

Mature Anterior Wall MIMature Anterior Wall MI

Signs Of An Signs Of An

Inferior Wall InfarctionInferior Wall Infarction

Inferior Wall InfarctionInferior Wall Infarction This infarction occurs on This infarction occurs on

the diaphragmatic surface the diaphragmatic surface of the heart.of the heart.

It is frequently caused by It is frequently caused by an occlusion to blood flow an occlusion to blood flow through the right coronarythrough the right coronary

ST Segment Changes ST Segment Changes With An Acute Inferior MIWith An Acute Inferior MI

ST segment elevations in ST segment elevations in Leads II, III and aVFLeads II, III and aVF

Reciprocal ST segment Reciprocal ST segment changes in Leads I, aVL, changes in Leads I, aVL, V1-V6.V1-V6.

Acute Inferior Myocardial InfarctionAcute Inferior Myocardial Infarctionhttp://homepages.enterprise.net/djenkins/ami.htmlhttp://homepages.enterprise.net/djenkins/ami.html

In An Uncomplicated MI, In An Uncomplicated MI, These EKG Changes Will These EKG Changes Will Largely Disappear Once Largely Disappear Once The Infarction Has The Infarction Has Frankly Resolved - Frankly Resolved - Usually In About 3 Days. Usually In About 3 Days.

A Mature Inferior Wall A Mature Inferior Wall MIMI

Old Inferior Wall MIOld Inferior Wall MI

Signs Of A Signs Of A

Lateral Wall InfarctionLateral Wall Infarction

Lateral Wall InfarctionLateral Wall Infarction

This type of MI involves the This type of MI involves the lateral wall of the heart - the lateral wall of the heart - the left ventricle.left ventricle.

It is often caused by an It is often caused by an occlusion to blood flow occlusion to blood flow through the circumflex artery.through the circumflex artery.

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

Acute Lateral Wall MIAcute Lateral Wall MI

In An Uncomplicated MI, In An Uncomplicated MI, These EKG Changes Will These EKG Changes Will Largely Disappear Once Largely Disappear Once The Infarction Has The Infarction Has Frankly Resolved - Frankly Resolved - Usually In About 3 Days. Usually In About 3 Days.

Mature Lateral Wall Mature Lateral Wall InfarctInfarct

For All Types Of MI’s, The For All Types Of MI’s, The Q Wave Often Remains As Q Wave Often Remains As The Only Residual Sign The Only Residual Sign That An Infarction Has That An Infarction Has Occurred. Also, The ST Occurred. Also, The ST Segment May Be Segment May Be Permanently Depressed.Permanently Depressed.

ST Segment DepressionST Segment Depression

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

ST Segment DepressionST Segment Depression

Types Of Types Of ST Segment DepressionST Segment Depression

ST Segment Depression ST Segment Depression May Be A Permanent May Be A Permanent Part Of The EKG Tracing.Part Of The EKG Tracing.

At Rest The Patient May At Rest The Patient May Have A Normal ST Segment. Have A Normal ST Segment. However, It May Become However, It May Become Depressed As The Person’s Depressed As The Person’s Exercise Level Is Increased Exercise Level Is Increased Above The Heart’s Ability To Above The Heart’s Ability To Receive Adequate Perfusion.Receive Adequate Perfusion.

The ST segment depression The ST segment depression will begin to appear as the will begin to appear as the heart becomes ischemicheart becomes ischemic

It will continue to be more It will continue to be more depressed the more depressed the more ischemic the heart ischemic the heart becomes.becomes.

The ST segment will The ST segment will normalize once the exercise normalize once the exercise intensity is reduced to a intensity is reduced to a level in which the heart level in which the heart receives enough perfusion to receives enough perfusion to support the work that is support the work that is being demanded.being demanded.

The T WaveThe T Wave

The T Wave Represents The T Wave Represents Repolarization Of The Repolarization Of The Ventricles.Ventricles.

Repolarization Proceeds Repolarization Proceeds From The Apex Of The From The Apex Of The Heart To The Base Of The Heart To The Base Of The Heart.Heart.

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

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

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

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

T Waves Get Taller T Waves Get Taller During GXT’s And During GXT’s And Exercise.Exercise.

T Waves During T Waves During InfarctionInfarction

With infarction, the T wave With infarction, the T wave usually becomes tall and usually becomes tall and narrow - referred to as narrow - referred to as “peaking”. “peaking”.

With time and the onset of With time and the onset of ischemia, the T wave will ischemia, the T wave will invert.invert.

The QT IntervalThe QT Interval

The QT Interval The QT Interval Encompasses The Time Encompasses The Time From The Beginning Of From The Beginning Of The Q Or R Wave The Q Or R Wave Through The End Of The Through The End Of The T Wave.T Wave.

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

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

Summary Of Durations & Summary Of Durations & Amplitudes Of The P-QRS-Amplitudes Of The P-QRS-

TT

P WavesP WavesNormal Duration : 2.5 mm Normal Duration : 2.5 mm Normal Amplitude : 2-3 mmNormal Amplitude : 2-3 mm

PR IntervalsPR Intervals Normal Duration : 3-5 mmNormal Duration : 3-5 mm

Q WavesQ WavesNormal Duration : Normal Duration : << .5 mm .5 mmNormal Amplitude : <25% of Normal Amplitude : <25% of R amplitude or R amplitude or ~~ 1.0 mm 1.0 mm

QRS ComplexQRS ComplexNormal Duration : Normal Duration : << 3.0 mm 3.0 mmNormal Amplitude : Variable Normal Amplitude : Variable

ST SegmentST SegmentNormal Amplitude : 1-2 mmNormal Amplitude : 1-2 mmNormal Duration : 2-3 mmNormal Duration : 2-3 mm

T WaveT WaveNormal Duration : 2 mmNormal Duration : 2 mmNormal Amplitude : < 5 Normal Amplitude : < 5 mm in Limb Leads & < 10 mm in Limb Leads & < 10 mm in Precordial Leads mm in Precordial Leads