12-Lead 12-Lead ElectrocardiographyElectrocardiography

a comprehensive course

Adam Thompson, EMT-P, A.S.Adam Thompson, EMT-P, A.S.

Lesson

1

ResourceResource

Course ObjectivesCourse Objectives

• Learn the basic concept behind electrical vectors.Learn the basic concept behind electrical vectors.• Learn the 6 step process to 12-lead ECG interpretation.Learn the 6 step process to 12-lead ECG interpretation.• Learn how to identify chamber enlargement.Learn how to identify chamber enlargement.• Learn how to differentiate between atrial & ventricular Learn how to differentiate between atrial & ventricular

rhythms.rhythms.• Learn how to identify bundle branch blocks.Learn how to identify bundle branch blocks.• Learn how to differentiate a STEMI from STE-MimicLearn how to differentiate a STEMI from STE-Mimic• Learn when to perform a right-sided or posterior 12-lead Learn when to perform a right-sided or posterior 12-lead

ECG.ECG.

Lesson OneLesson One

• Learn the appropriate placement of the 12-Learn the appropriate placement of the 12-lead ECG electrodes.lead ECG electrodes.

• Learn how to eliminate artifact and obtain a Learn how to eliminate artifact and obtain a clean recording.clean recording.

• Learn about the 6 step interpretation process.Learn about the 6 step interpretation process.• Learn and apply the ability to determine rate Learn and apply the ability to determine rate

& rhythm.& rhythm.

12-Lead ECG

“In lead II? You’ve got NO clue.” - Bob Page

12-Lead Placement12-Lead Placement

V1V1 - 4th ICS, right of - 4th ICS, right of sternumsternumV2V2 - 4th ICS, left of - 4th ICS, left of sternumsternumV3V3 - Between V2 & V4 - Between V2 & V4V4V4 - 5th ICS, left - 5th ICS, left midclavicular linemidclavicular lineV5V5 - Lateral to V4, left - Lateral to V4, left anterior axillary lineanterior axillary lineV6V6 - Lateral to V5, left - Lateral to V5, left midaxillary linemidaxillary line

V1V1 - 4th ICS, right of - 4th ICS, right of sternumsternumV2V2 - 4th ICS, left of - 4th ICS, left of sternumsternumV3V3 - Between V2 & V4 - Between V2 & V4V4V4 - 5th ICS, left - 5th ICS, left midclavicular linemidclavicular lineV5V5 - Lateral to V4, left - Lateral to V4, left anterior axillary lineanterior axillary lineV6V6 - Lateral to V5, left - Lateral to V5, left midaxillary linemidaxillary line

Eliminate ArtifactEliminate Artifact

• The patient’s chest should be bare.The patient’s chest should be bare.• All hair that inhibits adequate electrode All hair that inhibits adequate electrode

contact should be shaved.contact should be shaved.• Benzoin tincture may be used to Benzoin tincture may be used to

enhance adhesive.enhance adhesive.

The Culprit ElectrodeThe Culprit Electrode

• Precordial leads are easy. V1 has artifact? Precordial leads are easy. V1 has artifact? Check V1 electrode.Check V1 electrode.

• If Leads I & III have artifact, check left If Leads I & III have artifact, check left shoulder.shoulder.

• If Leads I & II have artifact, check right If Leads I & II have artifact, check right shoulder.shoulder.

• Leads II & III? Check left leg electrode.Leads II & III? Check left leg electrode.

Precordial LeadsPrecordial Leads

Precordium - area of chest over heartPrecordium - area of chest over heart

Precordial LeadsPrecordial Leads

• Right Precordial LeadsRight Precordial Leads

Precordial LeadsPrecordial Leads

• Left Precordial LeadsLeft Precordial Leads

Limb LeadsLimb Leads

• Obtained from Red, White, Black, & Obtained from Red, White, Black, & Green electrodesGreen electrodes

Limb Leads Precordial Leads

Lead I aVR V1 V4

Lead II aVL V2 V5

Lead III aVF V3 V6

12 Leads12 Leads

Lead I aVR V1 V4

Lead II aVL V2 V5

Lead III aVF V3 V6

Contiguous LeadsContiguous Leads

Lead I

high lateral

aVR V1

septal

V4

anterior

Lead II

inferior

aVL

high lateral

V2

septal

V5

low lateral

Lead III

inferior

aVF

inferior

V3

anterior

V6

low lateral

Contiguous LeadsContiguous Leads

The 6-Step MethodThe 6-Step Method

• 1. Rate & Rhythm1. Rate & Rhythm• 2. Axis Determination2. Axis Determination• 3. Intervals3. Intervals• 4. Morphology4. Morphology• 5. STE-Mimics5. STE-Mimics• 6. Ischemia, Injury, & Infarct6. Ischemia, Injury, & Infarct

The 6-Step MethodThe 6-Step Method

Rate & RhythmRate & Rhythm

• What is your initial rhythm What is your initial rhythm interpretation?interpretation?

• Is the rhythm too fast or too slow?Is the rhythm too fast or too slow?• Are we certain it is supraventricular?Are we certain it is supraventricular?• If the QRS complexes are wide, it is If the QRS complexes are wide, it is

ventricular until proven otherwise.ventricular until proven otherwise.

The 6-Step MethodThe 6-Step Method

Axis DeterminationAxis Determination

• Is the axis normal?Is the axis normal?

• Is it left axis deviation? Is it left axis deviation?

• Is it right axis deviation?Is it right axis deviation?

• Extreme right axis deviation?Extreme right axis deviation?

• Consider pathologies!Consider pathologies!

The 6-Step MethodThe 6-Step Method

IntervalsIntervals

• Double check PR-interval and QRS Double check PR-interval and QRS durationduration

• Identify the QT or QTc intervalIdentify the QT or QTc interval

• Consider pathologies for abnormal Consider pathologies for abnormal intervals.intervals.

The 6-Step MethodThe 6-Step Method

MorphologyMorphology

• If QRS is wide, what is morphology in V1?If QRS is wide, what is morphology in V1?• Bundlebranch block?Bundlebranch block?• Bifascicular block?Bifascicular block?• Identify chamber enlargement.Identify chamber enlargement.• Consider T-wave morphologyConsider T-wave morphology• Consider possible pathologies that correlate Consider possible pathologies that correlate

with altered morphologies.with altered morphologies.

The 6-Step MethodThe 6-Step Method

STE-MimicsSTE-Mimics

• Determine if a paced rhythm, LBBB, LVH, Determine if a paced rhythm, LBBB, LVH, Early repol, pericarditis, WPW, or Early repol, pericarditis, WPW, or hyperkalemia is present.hyperkalemia is present.

• By this step, many possible pathologies have By this step, many possible pathologies have already been ruled out or in.already been ruled out or in.

The 6-Step MethodThe 6-Step Method

Ischemia, Injury, & InfarctIschemia, Injury, & Infarct

• Is it an obvious STEMI? ie. Tombstones?Is it an obvious STEMI? ie. Tombstones?• Identify ST-elevation, & ST-depression.Identify ST-elevation, & ST-depression.• Identify hyperacute T-waves or Q-waves.Identify hyperacute T-waves or Q-waves.• Consider reciprocal changes.Consider reciprocal changes.• Do you show changes in contiguous leads?Do you show changes in contiguous leads?• Consider culprit artery, and affected area of the heart.Consider culprit artery, and affected area of the heart.

12-Lead Basics

• Measurements are usually accurate

12-Lead Basics

• GE-Marquette 12SL Interpretive Algorhythm– Relatively reliable on clean ECG tracing.

12-Lead Basics

• The patient age and gender should always be entered into the 12-lead monitor.

12-Lead Basics

Typical 12-Lead ECG

12-Lead Basics

Typical 12-Lead ECG

12-Lead Basics

Typical 12-Lead ECG

12-Lead Basics

Typical 12-Lead ECG

12-Lead Basics

Typical 12-Lead ECG

12-Lead Basics

12-Lead Basics

Typical 12-Lead ECG

12-Lead Basics

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Rate & RhythmRate & Rhythm

• Interpret the rhythmInterpret the rhythm– Identify the rateIdentify the rate– Is it regular or irregular?Is it regular or irregular?– Identify P-wavesIdentify P-waves– Identify PR-intervalIdentify PR-interval

Rate & RhythmRate & Rhythm

Calculate the RateCalculate the Rate

150 100 75 60300

Rate & RhythmRate & Rhythm

• Is the rate too fast or too slow?Is the rate too fast or too slow?

• Intrinsic Rates:Intrinsic Rates:– SA Node - 60 to 100SA Node - 60 to 100– AV Junction - 40 to 60AV Junction - 40 to 60– Purkinje Fibers - 20 to 40Purkinje Fibers - 20 to 40

Rate & RhythmRate & Rhythm

Regular or IrregularRegular or Irregular

Rate & RhythmRate & Rhythm

Regular or IrregularRegular or Irregular

Rate & RhythmRate & Rhythm

P-WavesP-Waves

• Are P-waves present?Are P-waves present?

• Is there a P-wave for every QRS?Is there a P-wave for every QRS?

• Is there a QRS for every P-wave?Is there a QRS for every P-wave?

• Do the P-waves appear after the QRS?Do the P-waves appear after the QRS?

Rate & RhythmRate & Rhythm

PR-IntervalPR-Interval

• Is the PR-interval consistent?Is the PR-interval consistent?

• Is the PR-interval > 0.20 sec (200ms)?Is the PR-interval > 0.20 sec (200ms)?

• Does the PR-interval lengthen?Does the PR-interval lengthen?

Rate & RhythmRate & Rhythm

• The next step is to interpret the rhythm The next step is to interpret the rhythm that the patient is in.that the patient is in.

• The following is a brief ECG arrhythmia The following is a brief ECG arrhythmia review. review.

Sinus Rhythms

Normal Sinus RhythmNormal Sinus Rhythm• Rate: 60 - 100 bpmRate: 60 - 100 bpm• Rhythm: Regularly RegularRhythm: Regularly Regular• P wave: PresentP wave: Present• P:QRS ratio: 1 to 1P:QRS ratio: 1 to 1• PR-interval: NormalPR-interval: Normal• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Normal Sinus Rhythm

Normal Sinus Rhythm

Normal Sinus Rhythm

Normal Sinus Rhythm

Normal Sinus Rhythm

Sinus ArrhythmiaSinus Arrhythmia• Rate: 60 - 100 bpmRate: 60 - 100 bpm• Rhythm: Varies with respirationRhythm: Varies with respiration• P wave: PresentP wave: Present• P:QRS ratio: 1 to 1P:QRS ratio: 1 to 1• PR-interval: NormalPR-interval: Normal• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Sinus ArrhythmiaSinus Arrhythmia

Sinus BradycardiaSinus Bradycardia• Rate: < 60 bpmRate: < 60 bpm• Rhythm: Regularly-RegularRhythm: Regularly-Regular• P wave: PresentP wave: Present• P:QRS ratio: 1 to 1P:QRS ratio: 1 to 1• PR-interval: NormalPR-interval: Normal• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Sinus Bradycardia

Sinus Bradycardia

Sinus Bradycardia

Sinus Bradycardia

Sinus TachycardiaSinus Tachycardia• Rate: > 100 bpmRate: > 100 bpm• Rhythm: Regularly-RegularRhythm: Regularly-Regular• P wave: PresentP wave: Present• P:QRS ratio: 1 to 1P:QRS ratio: 1 to 1• PR-interval: NormalPR-interval: Normal• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Sinus Tachycardia

Sinus Tachycardia

Sinus Tachycardia

Sinus Tachycardia

Sinus Pause/ArrestSinus Pause/Arrest• Rate: VariesRate: Varies• Rhythm: IrregularRhythm: Irregular• P wave: Present except for pauseP wave: Present except for pause• P:QRS ratio: 1 to 1P:QRS ratio: 1 to 1• PR-interval: NormalPR-interval: Normal• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Premature Atrial ContractionPremature Atrial Contraction• Rate: Determine underlined rateRate: Determine underlined rate• Rhythm: IrregularRhythm: Irregular• P wave: Present, may be different w/ PACP wave: Present, may be different w/ PAC• P:QRS ratio: 1 to 1P:QRS ratio: 1 to 1• PR-interval: Normal, may vary w/ PACPR-interval: Normal, may vary w/ PAC• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Ectopic Atrial TachycardiaEctopic Atrial Tachycardia• Rate: 100 - 180 bpmRate: 100 - 180 bpm• Rhythm: RegularRhythm: Regular• P wave: Present, may be different w/ ectopyP wave: Present, may be different w/ ectopy• P:QRS ratio: 1 to 1P:QRS ratio: 1 to 1• PR-interval: Normal, different w/ ectopyPR-interval: Normal, different w/ ectopy• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Wandering Atrial PacemakerWandering Atrial Pacemaker• Rate: < 100 bpmRate: < 100 bpm• Rhythm: Rhythm: Irregularly-IrregularIrregularly-Irregular• P wave: At least 3 different morphologiesP wave: At least 3 different morphologies• P:QRS ratio: 1 to 1P:QRS ratio: 1 to 1• PR-interval: VariablePR-interval: Variable• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Multifocal Atrial TachycardiaMultifocal Atrial Tachycardia• Rate: > 100 bpmRate: > 100 bpm• Rhythm: Rhythm: Irregularly-IrregularIrregularly-Irregular• P wave: At least 3 different morphologiesP wave: At least 3 different morphologies• P:QRS ratio: 1 to 1P:QRS ratio: 1 to 1• PR-interval: VariablePR-interval: Variable• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Atrial Flutter

Atrial FlutterAtrial Flutter• Rate: Atria (250-350), Ventricles (125-175)Rate: Atria (250-350), Ventricles (125-175)• Rhythm: Rhythm: Usually RegularUsually Regular• P wave: Saw toothed “F waves”P wave: Saw toothed “F waves”• P:QRS ratio: Variable, 2:1 is commonP:QRS ratio: Variable, 2:1 is common• PR-interval: VariablePR-interval: Variable• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Atrial Flutter

3:1

Atrial Flutter

2:1

Atrial Fibrillation

Atrial Fibrillation

Atrial FibrillationAtrial Fibrillation• Rate: Variable, depending on ventriclesRate: Variable, depending on ventricles• Rhythm: Rhythm: Irregularly-IrregularIrregularly-Irregular• P wave: None, chaotic atrial activityP wave: None, chaotic atrial activity• P:QRS ratio: NoneP:QRS ratio: None• PR-interval: NonePR-interval: None• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Atrial Fibrillation

Atrial Fibrillation

Atrial Fibrillation

Atrial Fibrillation

Premature Junctional Premature Junctional ContractionContraction

• Rate: Determine underlying rhythmRate: Determine underlying rhythm• Rhythm: Rhythm: IrregularIrregular• P wave: none, antegrade, or retrogradeP wave: none, antegrade, or retrograde• P:QRS ratio: 1:1 or retrogradeP:QRS ratio: 1:1 or retrograde• PR-interval: None, short, or retrogradePR-interval: None, short, or retrograde• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Junctional Escape BeatJunctional Escape Beat

• Rate: Determine underlying rhythmRate: Determine underlying rhythm• Rhythm: Rhythm: IrregularIrregular• P wave: none, antegrade, or retrogradeP wave: none, antegrade, or retrograde• P:QRS ratio: 1:1 or retrogradeP:QRS ratio: 1:1 or retrograde• PR-interval: None, short, or retrogradePR-interval: None, short, or retrograde• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Junctional RhythmJunctional Rhythm

• Rate: 40 - 60 bpmRate: 40 - 60 bpm• Rhythm: Rhythm: RegularRegular• P wave: none, antegrade, or retrogradeP wave: none, antegrade, or retrograde• P:QRS ratio: 1:1 or retrogradeP:QRS ratio: 1:1 or retrograde• PR-interval: None, short, or retrogradePR-interval: None, short, or retrograde• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Accelerated Junctional RhythmAccelerated Junctional Rhythm

• Rate: 60 - 100 bpmRate: 60 - 100 bpm• Rhythm: Rhythm: RegularRegular• P wave: none, antegrade, or retrogradeP wave: none, antegrade, or retrograde• P:QRS ratio: 1:1 or retrogradeP:QRS ratio: 1:1 or retrograde• PR-interval: None, short, or retrogradePR-interval: None, short, or retrograde• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

Narrow Complex TachycardiaNarrow Complex Tachycardia

Sinus Tach

MAT

Ectopic A-Tach

Junctional

AVNRT/AVRT

A-Flutter

P

P

P

P

P

F F F F

P FP-Wave Flutter Wave

Premature Ventricular Premature Ventricular ContractionContraction

• Rate: Determine underlying rhythmRate: Determine underlying rhythm• Rhythm: Rhythm: IrregularIrregular• P wave: None with PVCP wave: None with PVC• P:QRS ratio: NoneP:QRS ratio: None• PR-interval: NonePR-interval: None• QRS Width: > 120 ms (0.12 sec) WIDEQRS Width: > 120 ms (0.12 sec) WIDE

Premature Ventricular ContractionPremature Ventricular Contraction

• Polymorphic– More than one one shape of QRS complex

• Multifocal– More than one focus or site of initial

impulse.

Premature Ventricular ContractionPremature Ventricular Contraction

1 2

Ventricular Escape BeatVentricular Escape Beat

• Rate: Determine underlying rhythmRate: Determine underlying rhythm• Rhythm: Rhythm: IrregularIrregular• P wave: None with PVCP wave: None with PVC• P:QRS ratio: NoneP:QRS ratio: None• PR-interval: NonePR-interval: None• QRS Width: > 120 ms (0.12 sec) WIDEQRS Width: > 120 ms (0.12 sec) WIDE

Ventricular Rhythms

Idioventricular RhythmIdioventricular Rhythm

• Rate: 20 - 40 bpmRate: 20 - 40 bpm• Rhythm: Rhythm: RegularRegular• P wave: NoneP wave: None• P:QRS ratio: NoneP:QRS ratio: None• PR-interval: NonePR-interval: None• QRS Width: > 120 ms (0.12 sec) WIDEQRS Width: > 120 ms (0.12 sec) WIDE

Idioventricular RhythmIdioventricular Rhythm

Accelerated Ventricular RhythmAccelerated Ventricular Rhythm

• Rate: 40 - 100 bpmRate: 40 - 100 bpm• Rhythm: Rhythm: RegularRegular• P wave: NoneP wave: None• P:QRS ratio: NoneP:QRS ratio: None• PR-interval: NonePR-interval: None• QRS Width: > 120 ms (0.12 sec) WIDEQRS Width: > 120 ms (0.12 sec) WIDE

Ventricular TachycardiaVentricular Tachycardia

• Rate: 100 - 200 bpmRate: 100 - 200 bpm• Rhythm: Rhythm: RegularRegular• P wave: None, complete AV disassociationP wave: None, complete AV disassociation• P:QRS ratio: NoneP:QRS ratio: None• PR-interval: NonePR-interval: None• QRS Width: > 120 ms (0.12 sec) WIDEQRS Width: > 120 ms (0.12 sec) WIDE

Ventricular TachycardiaVentricular Tachycardia

Torsade de PointesTorsade de Pointes

• Rate: 200 - 250 bpmRate: 200 - 250 bpm• Rhythm: Rhythm: IrregularIrregular• P wave: NoneP wave: None• P:QRS ratio: NoneP:QRS ratio: None• PR-interval: NonePR-interval: None• QRS Width: > 120 ms (0.12 sec) WIDEQRS Width: > 120 ms (0.12 sec) WIDE

Ventricular FibrillationVentricular Fibrillation

• Rate: IndeterminateRate: Indeterminate• Rhythm: Rhythm: ChaoticChaotic• P wave: NoneP wave: None• P:QRS ratio: NoneP:QRS ratio: None• PR-interval: NonePR-interval: None• QRS Width: NoneQRS Width: None

1st Degree Heart Block1st Degree Heart Block

• Rate: Identify underlying rateRate: Identify underlying rate• Rhythm: Rhythm: RegularRegular• P wave: PresentP wave: Present• P:QRS ratio: 1 to 1P:QRS ratio: 1 to 1• PR-interval: > 200 ms (0.20 sec)PR-interval: > 200 ms (0.20 sec)• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

1st Degree Heart Block1st Degree Heart Block

2nd Degree Heart Block - Type I2nd Degree Heart Block - Type I

• Rate: Identify underlying rateRate: Identify underlying rate• Rhythm: Rhythm: Regularly-IrregularRegularly-Irregular• P wave: PresentP wave: Present• P:QRS ratio: VariableP:QRS ratio: Variable• PR-interval: Variable (going, going, gone…)PR-interval: Variable (going, going, gone…)• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

2nd Degree Heart Block - Type I2nd Degree Heart Block - Type I

1st Degree AVB 2nd Degree AVB - Type I

2nd Degree Heart Block - Type II2nd Degree Heart Block - Type II

• Rate: Identify underlying rateRate: Identify underlying rate• Rhythm: Rhythm: Regularly-IrregularRegularly-Irregular• P wave: PresentP wave: Present• P:QRS ratio: x:x - 1P:QRS ratio: x:x - 1• PR-interval: Normal *Dropped QRSPR-interval: Normal *Dropped QRS• QRS Width: < 120 ms (0.12 sec)QRS Width: < 120 ms (0.12 sec)

3rd Degree Heart Block 3rd Degree Heart Block

• Rate: Atrial & Ventricular rates differRate: Atrial & Ventricular rates differ• Rhythm: Rhythm: RegularRegular• P wave: PresentP wave: Present• P:QRS ratio: VariableP:QRS ratio: Variable• PR-interval: No patternPR-interval: No pattern• QRS Width: Normal or WIDEQRS Width: Normal or WIDE

3rd Degree Heart Block3rd Degree Heart Block

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3rd Degree Heart Block3rd Degree Heart Block

AV Blocks

Yes2nd Degree Type II

No1st Degree

YesDropped QRS?

Yes2nd Degree Type I

No3rd Degree

NoP-wave for every QRS?

Is the PR-interval a constant length?

Interpretation Pearl

• When interpreting an ECG rhythm, always consider the company it keeps. – Associated Signs & Symptoms – Past medical history– Medications…etc

ECG Rhythms

• You must understand the basic ECG arrhythmias prior to moving on.

• Review the previous slides until you think you’ve got it.

• The next slide may assist you if you’re still having a hard time.

The ECG Dance

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The Golden Rule

ECG Interpretation is largely based on THEORY.

Give five cardiologists the same ECG to interpret, and you may receive five different interpretations.

The End

• End of Lesson 1

• Lesson 2 will include axis determination