Basics of EKG Basics of EKG InterpretationInterpretation

Arnold Seto, MD, MPAArnold Seto, MD, MPA

Chief of CardiologyChief of Cardiology

Long Beach VA Medical Long Beach VA Medical CenterCenter

OutlineOutline

1.1. Review of the conduction systemReview of the conduction system

2.2. QRS breakdownQRS breakdown

3.3. RateRate

4.4. AxisAxis

5.5. RhythmsRhythms

The Normal Conduction SystemThe Normal Conduction System

Waveforms and IntervalsWaveforms and Intervals

EKG LeadsEKG Leads

The standard EKG has 12 The standard EKG has 12 leads:leads:

3 Standard Limb Leads

3 Augmented Limb Leads

6 Precordial Leads

The axis of a particular lead represents the viewpoint from The axis of a particular lead represents the viewpoint from which it looks at the heart.which it looks at the heart.

Standard Limb LeadsStandard Limb Leads

All Limb LeadsAll Limb Leads

Precordial LeadsPrecordial Leads

Adapted from: www.numed.co.uk/electrodepl.html

Precordial LeadsPrecordial Leads

Anatomic GroupsAnatomic Groups(Summary)(Summary)

RateRate

►Rule of 300Rule of 300

►10 Second Rule10 Second Rule

Rule of 300Rule of 300

Take the number of “big boxes” Take the number of “big boxes” between neighboring QRS complexes, between neighboring QRS complexes, and divide this into 300. The result will and divide this into 300. The result will be approximately equal to the ratebe approximately equal to the rate

Although fast, this method only works Although fast, this method only works for regular rhythms.for regular rhythms.

What is the heart rate?What is the heart rate?

(300 / 6) = 50 bpm

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What is the heart rate?What is the heart rate?

(300 / ~ 4) = ~ 75 bpm

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What is the heart rate?What is the heart rate?

(300 / 1.5) = 200 bpm

The Rule of 300The Rule of 300

It may be easiest to memorize the following table:It may be easiest to memorize the following table:

# of big # of big boxesboxes

RateRate

11 300300

22 150150

33 100100

44 7575

55 6060

66 5050

10 Second Rule10 Second Rule

As most EKGs record 10 seconds of rhythm As most EKGs record 10 seconds of rhythm per page, one can simply count the number of per page, one can simply count the number of beats present on the EKG and multiply by 6 to beats present on the EKG and multiply by 6 to get the number of beats per 60 seconds.get the number of beats per 60 seconds.

This method works well for irregular rhythms.This method works well for irregular rhythms.

What is the heart rate?What is the heart rate?

33 x 6 = 198 bpm

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The QRS AxisThe QRS Axis

By near-consensus, the normal QRS axis is defined as ranging from -30° to +90°.

-30° to -90° is referred to as a left axis deviation (LAD)

+90° to +180° is referred to as a right axis deviation (RAD)

Determining the AxisDetermining the Axis

►The Quadrant ApproachThe Quadrant Approach

►The Equiphasic ApproachThe Equiphasic Approach

Determining the AxisDetermining the Axis

Predominantly Positive

Predominantly Negative

Equiphasic

The Quadrant ApproachThe Quadrant Approach1. Examine the QRS complex in leads I and aVF to 1. Examine the QRS complex in leads I and aVF to

determine if they are predominantly positive or determine if they are predominantly positive or predominantly negative. The combination should predominantly negative. The combination should place the axis into one of the 4 quadrants below.place the axis into one of the 4 quadrants below.

The Quadrant ApproachThe Quadrant Approach2. In the event that LAD is present, examine lead II to 2. In the event that LAD is present, examine lead II to

determine if this deviation is pathologic. If the QRS determine if this deviation is pathologic. If the QRS in II is predominantly positive, the LAD is non-in II is predominantly positive, the LAD is non-pathologic (in other words, the axis is normal). If it is pathologic (in other words, the axis is normal). If it is predominantly negative, it is pathologic. predominantly negative, it is pathologic.

Quadrant Approach: Example 1Quadrant Approach: Example 1

Negative in I, positive in aVF RAD

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Quadrant Approach: Example 2Quadrant Approach: Example 2

Positive in I, negative in aVF Predominantly positive in II

Normal Axis (non-pathologic LAD)

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The Equiphasic ApproachThe Equiphasic Approach

1. Determine which lead contains the most equiphasic 1. Determine which lead contains the most equiphasic QRS complex. The fact that the QRS complex in QRS complex. The fact that the QRS complex in this lead is equally positive and negative indicates this lead is equally positive and negative indicates that the net electrical vector (i.e. overall QRS axis) that the net electrical vector (i.e. overall QRS axis) is perpendicular to the axis of this particular lead.is perpendicular to the axis of this particular lead.

2. Examine the QRS complex in whichever lead lies 2. Examine the QRS complex in whichever lead lies 90° away from the lead identified in step 1. If the 90° away from the lead identified in step 1. If the QRS complex in this second lead is predominantly QRS complex in this second lead is predominantly positive, than the axis of this lead is approximately positive, than the axis of this lead is approximately the same as the net QRS axis. If the QRS complex the same as the net QRS axis. If the QRS complex is predominantly negative, than the net QRS axis is predominantly negative, than the net QRS axis lies 180° from the axis of this lead.lies 180° from the axis of this lead.

Equiphasic Approach: Example 1Equiphasic Approach: Example 1

Equiphasic in aVF Predominantly positive in I QRS axis ≈ 0°

The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/

Equiphasic Approach: Example 2Equiphasic Approach: Example 2

Equiphasic in II Predominantly negative in aVL QRS axis ≈ +150°

The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/

Systematic ApproachSystematic Approach► Rate Rate ► RhythmRhythm► AxisAxis► Wave MorphologyWave Morphology

P, T, and U waves and QRS P, T, and U waves and QRS complexcomplex

► IntervalsIntervals PR, QRS, QTPR, QRS, QT

► ST SegmentST Segment

Rhythms/ArrhythmiasRhythms/Arrhythmias

►SinusSinus

►AtrialAtrial

► JunctionalJunctional

►VentricularVentricular

Sinus Rhythms: Criteria/TypesSinus Rhythms: Criteria/Types

► P waves upright in I, II, aVFP waves upright in I, II, aVF

► Constant P-P/R-R intervalConstant P-P/R-R interval

► RateRate

► Narrow QRS complexNarrow QRS complex

► P:QRS ratio 1:1P:QRS ratio 1:1

► P-R interval is normal and constantP-R interval is normal and constant

Sinus Arrhythmias: Sinus Arrhythmias: Criteria/TypesCriteria/Types

►Normal Sinus RhythmNormal Sinus Rhythm

►Sinus BradycardiaSinus Bradycardia

►Sinus TachycardiaSinus Tachycardia

►Sinus ArrhythmiaSinus Arrhythmia

Normal Sinus RhythmNormal Sinus Rhythm

• Rate is 60 to 100

Sinus BradycardiaSinus Bradycardia

• Can be normal variant

• Can result from medication

• Look for underlying cause

Sinus TachycardiaSinus Tachycardia

• May be caused by exercise, fever, hyperthyroidism

• Look for underlying cause, slow the rate

Sinus ArrhythmiaSinus Arrhythmia

• Seen in young patients

• Secondary to breathing

• Heart beats faster

Atrial Arrhythmias: Atrial Arrhythmias: Criteria/TypesCriteria/Types

►P waves inverted in I, II and aVFP waves inverted in I, II and aVF

►Abnormal shapeAbnormal shape NotchedNotched

FlattenedFlattened

DiphasicDiphasic

►Narrow QRS complexNarrow QRS complex

Atrial Arrhythmias: Atrial Arrhythmias: Criteria/TypesCriteria/Types

►Premature Atrial ContractionsPremature Atrial Contractions►Ectopic Atrial RhythmEctopic Atrial Rhythm►Wandering Atrial PacemakerWandering Atrial Pacemaker►Multifocal Atrial TachycardiaMultifocal Atrial Tachycardia►Atrial FlutterAtrial Flutter►Atrial FibrillationAtrial Fibrillation

Premature Atrial ContractionPremature Atrial Contraction

• QRS complex narrow

• RR interval shorter than sinus QRS complexes

• P wave shows different morphology than sinus P wave

Ectopic Atrial RhythmEctopic Atrial Rhythm

• Narrow QRS complex

• P wave inverted

Wandering Atrial PacemakerWandering Atrial Pacemaker

• 3 different P wave morphologies

possible with ventricular rate < 100 bpm

Multifocal Atrial TachycardiaMultifocal Atrial Tachycardia

• 3 different P wave morphologies

with ventricular rate> 100 bpm

Atrial FlutterAtrial Flutter

• Regular ventricular rate 150 bpm

• Varying ratios of F waves to QRS

complexes, most common is 4:1

• Tracing shows 2:1 conduction

Atrial FlutterAtrial Flutter

• Tracing shows 6:1 conduction

Atrial FibrillationAtrial Fibrillation

• Tracing shows irregularly irregular rhythm with no P waves

• Ventricular rate usually > 100 bpm

Atrial FibrillationAtrial Fibrillation

• Tracing shows irregularly irregular

rhythm with no P waves

• Ventricular rate is 40

Atrial TachycardiaAtrial Tachycardia

• Tracing shows regular ventricular rate with P waves that are different from sinus

P waves

• Ventricular rate is usually 150 to 250 bpm

AV Nodal BlocksAV Nodal Blocks

• Delay conduction of impulses from

sinus node

• If AV node does not let impulse

through, no QRS complex is seen

• AV nodal block classes:

1st, 2nd, 3rd degree

11stst Degree AV Block Degree AV Block

• PR interval constant

• >.2 sec

• All impulses conducted

22ndnd Degree AV Block Type 1 Degree AV Block Type 1

• AV node conducted each impulse slower and finally no impulse is conducted

• Longer PR interval, finally no QRS complex

22ndnd Degree AV Block Type 2 Degree AV Block Type 2

• Constant PR interval

• AV node intermittently conducts no impulse

• AV node conducts no impulse

• Atria and ventricles beat at intrinsic rate (80 and 40 respectively)

• No association between P waves and QRS complexes

33rdrd Degree AV Block Degree AV Block

• Caused by bypass tract

• AV node is bypassed, delay

• EKG shows short PR interval <.11 sec

• Upsloping to QRS complex (delta wave)

Another Consideration: Another Consideration: Wolfe-Parkinson-White (WPW)Wolfe-Parkinson-White (WPW)

• Delta wave, short PR interval

WPWWPW

Ventricular Arrhythmias: Ventricular Arrhythmias: Criteria/TypesCriteria/Types

► Wide QRS Wide QRS complexcomplex

► Rate : Rate : variablevariable

► No P wavesNo P waves

► Premature Ventricular Premature Ventricular ContractionsContractions

► Idioventricular RhythmIdioventricular Rhythm

► Accelerated IVRAccelerated IVR

► Ventricular TachycardiaVentricular Tachycardia

► Ventricular FibrillationVentricular Fibrillation

• Occurs earlier than sinus beat

• Wide, no P wave

Premature Ventricular Premature Ventricular ContractionContraction

• Escape rhythm

• Rate is 20 to 40 bpm

Idioventricular RhythmIdioventricular Rhythm

• Rate is 40 to 100 bpm

Accelerated Idioventricular Accelerated Idioventricular RhythmRhythm

• Rate is > than 100 bpm

Ventricular TachycardiaVentricular Tachycardia

Torsades de PointesTorsades de Pointes

• Occurs secondary to prolonged QT interval

• Unorganized activity of ventricle

Ventricular Ventricular Tachycardia/FibrillationTachycardia/Fibrillation

Ventricular FibrillationVentricular Fibrillation

Chamber Chamber EnlargementsEnlargements

► Differential DiagnosisDifferential Diagnosis Hypertension (HTN)Hypertension (HTN) Aortis Stenosis (AS)Aortis Stenosis (AS) Aortic Insufficiency (AI)Aortic Insufficiency (AI) Hypertrophic Cardiomyopathy (HCM)Hypertrophic Cardiomyopathy (HCM) Mitral Regurgitation (MR)Mitral Regurgitation (MR) Coarctation of the Aorta (COA) Coarctation of the Aorta (COA) Physiologic Physiologic

Left Ventricular Hypertrophy Left Ventricular Hypertrophy (LVH)(LVH)

► False positiveFalse positive Thin chest wallThin chest wall Status post mastectomyStatus post mastectomy Race, Sex, AgeRace, Sex, Age Left Bundle Branch Block (LBBB)Left Bundle Branch Block (LBBB) Acute MIAcute MI Left Anterior Fascicular BlockLeft Anterior Fascicular Block Incorrect standardizationIncorrect standardization

Left Ventricular Hypertrophy Left Ventricular Hypertrophy (LVH)(LVH)

EKG Criteria: Diagnosis of EKG Criteria: Diagnosis of LVHLVH

LVH with StrainLVH with Strain

Right Ventricular HypertrophyRight Ventricular Hypertrophy

►Reversal of precordial patternReversal of precordial pattern

R waves prominent in V1 and V2R waves prominent in V1 and V2

S waves smaller in V1 and V2S waves smaller in V1 and V2

S waves become prominent in V5 S waves become prominent in V5 and V6and V6

Right Ventricular HypertrophyRight Ventricular Hypertrophy

Right Ventricular Hypertrophy: Right Ventricular Hypertrophy: CausesCauses

► Chronic Obstructive Pulmonary DiseaseChronic Obstructive Pulmonary Disease► Pulmonary HTNPulmonary HTN

PrimaryPrimary► Pulmonary EmbolusPulmonary Embolus► Mitral StenosisMitral Stenosis► Mitral RegurgitationMitral Regurgitation► Chronic LV failureChronic LV failure

Right Ventricular Hypertrophy: Right Ventricular Hypertrophy: CausesCauses

►Tricuspid RegurgitationTricuspid Regurgitation

►Atrial Septal DefectAtrial Septal Defect

►Pulmonary StenosisPulmonary Stenosis

►Tetralogy of FallotTetralogy of Fallot

►Ventricular Septal DefectVentricular Septal Defect

► Mitral StenosisMitral Stenosis

► Mitral RegurgitationMitral Regurgitation

► Left ventricular hypertrophyLeft ventricular hypertrophy

► HypertensionHypertension

► Aortic StenosisAortic Stenosis

► Aortic InsufficiencyAortic Insufficiency

► Hypertrophic CardiomyopathyHypertrophic Cardiomyopathy

Left Atrial Enlargement: CausesLeft Atrial Enlargement: Causes

Left Atrial Enlargement: Left Atrial Enlargement: CriteriaCriteria

► P waveP wave

► Notch in P waveNotch in P wave Any leadAny lead Peaks > 0.04 secsPeaks > 0.04 secs

► V1 V1 Terminal portion of P wave Terminal portion of P wave >> 1mm 1mm

deep and deep and >> 0.04 sec wide 0.04 sec wide

Lead IILead II

P Wave: Left Atrial P Wave: Left Atrial EnlargementEnlargement

Left Atrial EnlargementLeft Atrial EnlargementLead V1Lead V1

► CHDCHD Tricuspid StenosisTricuspid Stenosis Pulmonary StenosisPulmonary Stenosis

► COPDCOPD► Pulmonary HTNPulmonary HTN► Pulmonary EmbolusPulmonary Embolus► Mitral RegurgitationMitral Regurgitation► Mitral StenosisMitral Stenosis

Right Atrial Enlargement: Right Atrial Enlargement: CausesCauses

►Tall, peaked P waveTall, peaked P wave

>> 2.5 mm in any lead 2.5 mm in any lead

►Most prominent P waves in leads I, Most prominent P waves in leads I,

II and aVFII and aVF

Right Atrial Enlargement: Right Atrial Enlargement: CriteriaCriteria

Right Atrial EnlargementRight Atrial Enlargement

Bundle Branch BlocksBundle Branch Blocks

Bundle Branch BlocksBundle Branch Blocks

►CompleteComplete QRS > .12 secsQRS > .12 secs

► IncompleteIncomplete QRS .10 - .12 secsQRS .10 - .12 secs

►LeftLeft CompleteComplete IncompleteIncomplete

►RightRight CompleteComplete IncompleteIncomplete

► Normal variantNormal variant

► Idiopathic degeneration of the Idiopathic degeneration of the

conduction systemconduction system

► CardiomyopathyCardiomyopathy

► Ischemic heart diseaseIschemic heart disease

► Aortic StenosisAortic Stenosis

► HyperkalemiaHyperkalemia

► Left Ventricular HypertrophyLeft Ventricular Hypertrophy

Left Bundle Branch Block: Left Bundle Branch Block: CausesCauses

Criteria for Left Bundle Criteria for Left Bundle Branch Block (LBBB)Branch Block (LBBB)

► Bizarre QRS MorphologyBizarre QRS Morphology High voltage S wave in V1, V2 & V3High voltage S wave in V1, V2 & V3 Tall R wave in leads I, aVL and V5-6Tall R wave in leads I, aVL and V5-6

► Often LADOften LAD► QRS IntervalQRS Interval► ST depression in leads I, aVL, & V5-V6ST depression in leads I, aVL, & V5-V6► T wave inversion in I, aVL, & V5-V6T wave inversion in I, aVL, & V5-V6

Left Bundle Branch BlockLeft Bundle Branch Block

Right Bundle Branch Block: Right Bundle Branch Block: Causes Causes

► Idiopathic degeneration of the Idiopathic degeneration of the conduction systemconduction system

► Ischemic heart diseaseIschemic heart disease►CardiomyopathyCardiomyopathy►Massive Pulmonary EmbolusMassive Pulmonary Embolus►Ventricular HypertrophyVentricular Hypertrophy►Normal VariantNormal Variant

Criteria for Right Bundle Criteria for Right Bundle Branch Block (RBBBBranch Block (RBBB))

► QRS morphologyQRS morphology Wide S wave in leads I and V4-V6Wide S wave in leads I and V4-V6 RSR’ pattern in leads V1, V2 and V3RSR’ pattern in leads V1, V2 and V3

► QRS durationQRS duration► ST depression in leads V1 and V2ST depression in leads V1 and V2► T wave inversion in leads V1 and V2T wave inversion in leads V1 and V2

Right Bundle Branch BlockRight Bundle Branch Block

Right Bundle Branch BlockRight Bundle Branch Block

Anterior Septal with RBBBAnterior Septal with RBBB

Ischemia and Ischemia and InfarctionInfarction

Normal Complexes and Normal Complexes and SegmentsSegments

J PointJ Point

IschemiaIschemia

•T wave inversion, ST segment depression

•Acute injury: ST segment elevation

•Dead tissue: Q wave

MeasurementsMeasurements

ST-Segment ElevationST-Segment Elevation

ST Segment DepressionST Segment Depression

Can be characterised as:-Can be characterised as:-

►DownslopingDownsloping

►UpslopingUpsloping

►HorizontalHorizontal

EKG Changes: Ischemia EKG Changes: Ischemia → → Acute Injury→ Infarction Acute Injury→ Infarction

Evolution of Transmural Evolution of Transmural InfarctionInfarction

Evolution of a Subendocardial Evolution of a Subendocardial InfarctionInfarction

Hyperacute T wavesHyperacute T waves

Q WavesQ Waves

Non Pathological Q wavesNon Pathological Q waves

Q waves of less than 2mm are normalQ waves of less than 2mm are normal

Pathological Q wavesPathological Q waves

Q waves of more than 2mm Q waves of more than 2mm

indicate full thickness myocardial indicate full thickness myocardial

damage from an infarctdamage from an infarct

Late sign of MI (evolved)Late sign of MI (evolved)

Look for Grouped Patterns Look for Grouped Patterns (Footprints)(Footprints)

►ST Depressions = IschemiaST Depressions = Ischemia

►ST Elevations = injuryST Elevations = injury

►Q Waves & T Wave Inversion = Q Waves & T Wave Inversion = InfarctionInfarction

Anterior Septal (Left Anterior Anterior Septal (Left Anterior Descending)Descending)

Anterior Lateral (Left Anterior Lateral (Left Circumflex)Circumflex)

Inferior (Right Coronary Inferior (Right Coronary Artery)Artery)

ST-T Wave ChangesST-T Wave Changes

Strain in HypertrophyStrain in Hypertrophy

Strain in LVHStrain in LVH

Strain in RVH Strain in RVH

Strain vs InfarctionStrain vs Infarction

PericarditisPericarditis

Digoxin ChangesDigoxin Changes

Ventricular AneurysmVentricular Aneurysm

T wavesT waves

SummarySummary

►Basic physiology of the conduction Basic physiology of the conduction systemsystem

►Origin of a normal EKGOrigin of a normal EKG

►Systematic approach to reading an Systematic approach to reading an EKGEKG

►Major abnormalities when reading Major abnormalities when reading an EKGan EKG