normal impulse conduction sinoatrial node av node bundle of his bundle branches purkinje fibers

Normal Impulse ConductionNormal Impulse Conduction

Sinoatrial nodeSinoatrial node

AV nodeAV node

Bundle of HisBundle of His

Bundle BranchesBundle Branches

Purkinje fibersPurkinje fibers

The Normal Conduction SystemThe Normal Conduction System

What is an EKG?What is an EKG?

The electrocardiogram (EKG) is a The electrocardiogram (EKG) is a representation of the electrical events of the representation of the electrical events of the cardiac cycle.cardiac cycle.

What types of pathology can we What types of pathology can we identify and study from EKGs?identify and study from EKGs?

ArrhythmiasArrhythmiasMyocardial ischemia and infarctionMyocardial ischemia and infarctionPericarditisPericarditisChamber hypertrophyChamber hypertrophyElectrolyte disturbances (i.e. Electrolyte disturbances (i.e. hyperkalemia, hypokalemia)hyperkalemia, hypokalemia)Drug toxicity (i.e. digoxin and drugs which Drug toxicity (i.e. digoxin and drugs which prolong the QT interval)prolong the QT interval)

Waveforms and IntervalsWaveforms and Intervals

Impulse Conduction & the ECGImpulse Conduction & the ECG

Sinoatrial nodeSinoatrial node

AV nodeAV node

Bundle of HisBundle of His

Bundle BranchesBundle Branches

Purkinje fibersPurkinje fibers

The “PQRST”The “PQRST”

P wave P wave - Atrial - Atrial depolarization depolarization

• T wave - Ventricular repolarization

• QRS - Ventricular depolarization

The PR IntervalThe PR Interval

Atrial depolarization Atrial depolarization

++

delay in AV junctiondelay in AV junction

(AV node/Bundle of His)(AV node/Bundle of His)

(delay allows time for (delay allows time for the atria to contract the atria to contract before the ventricles before the ventricles contract)contract)

Pacemakers of the HeartPacemakers of the Heart

SA NodeSA Node - Dominant pacemaker with an - Dominant pacemaker with an intrinsic rate of 60 - 100 beats/minute.intrinsic rate of 60 - 100 beats/minute.

AV NodeAV Node - Back-up pacemaker with an - Back-up pacemaker with an intrinsic rate of 40 - 60 beats/minute.intrinsic rate of 40 - 60 beats/minute.

Ventricular cellsVentricular cells - Back-up pacemaker with - Back-up pacemaker with an intrinsic rate of 20 - 45 bpm.an intrinsic rate of 20 - 45 bpm.

The ECG PaperThe ECG Paper

HorizontallyHorizontally– One small box - 0.04 sOne small box - 0.04 s– One large box - 0.20 s One large box - 0.20 s

VerticallyVertically– One large box - 0.5 mVOne large box - 0.5 mV

EKG LeadsEKG Leads

Leads are electrodes which measure the Leads are electrodes which measure the difference in electrical potential between difference in electrical potential between either:either:

1. Two different points on the body (bipolar leads)1. Two different points on the body (bipolar leads)

2. One point on the body and a virtual reference point 2. One point on the body and a virtual reference point with zero electrical potential, located in the center of with zero electrical potential, located in the center of the heart (unipolar leads)the heart (unipolar leads)

EKG LeadsEKG Leads

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

Rhythm AnalysisRhythm Analysis

Step 1:Step 1: Calculate rate.Calculate rate.Step 2: Determine axisStep 2: Determine axisStep 3:Step 3: Determine regularity.Determine regularity.Step 4:Step 4: Assess the P waves.Assess the P waves.Step 5:Step 5: Determine PR interval.Determine PR interval.Step 6:Step 6: Determine QRS duration.Determine QRS duration.

Standard Limb LeadsStandard Limb Leads

Standard Limb LeadsStandard Limb Leads

Augmented Limb LeadsAugmented Limb Leads

All Limb LeadsAll Limb Leads

Precordial LeadsPrecordial Leads

Precordial LeadsPrecordial Leads

Summary of LeadsSummary of Leads

Limb LeadsLimb Leads Precordial LeadsPrecordial Leads

BipolarBipolar I, II, IIII, II, III(standard limb leads)(standard limb leads)

--

UnipolarUnipolar aVR, aVL, aVF aVR, aVL, aVF (augmented limb leads)(augmented limb leads)

VV11-V-V66

Anatomic GroupsAnatomic Groups(Septum)(Septum)

Anatomic GroupsAnatomic Groups(Anterior Wall)(Anterior Wall)

Anatomic GroupsAnatomic Groups(Lateral Wall)(Lateral Wall)

Anatomic GroupsAnatomic Groups(Inferior Wall)(Inferior Wall)

Anatomic GroupsAnatomic Groups(Summary)(Summary)

Rule of 300Rule of 300

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

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

(300 / 6) = 50 bpm

www.uptodate.com

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

(300 / ~ 4) = ~ 75 bpm

www.uptodate.com

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

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

The QRS AxisThe QRS Axis

The QRS axis represents the net overall The QRS axis represents the net overall direction of the heart’s electrical activity.direction of the heart’s electrical activity.

Abnormalities of axis can hint at:Abnormalities of axis can hint at:

Ventricular enlargementVentricular enlargement

Conduction blocks (i.e. hemiblocks)Conduction blocks (i.e. hemiblocks)

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 determine 1. Examine the QRS complex in leads I and aVF to determine

if they are predominantly positive or predominantly if they are predominantly positive or predominantly negative. The combination should place the axis into one negative. The combination should place the axis into one of the 4 quadrants below.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 in II is determine if this deviation is pathologic. If the QRS in II is predominantly positive, the LAD is non-pathologic (in other predominantly positive, the LAD is non-pathologic (in other words, the axis is normal). If it is predominantly negative, it words, the axis is normal). If it is predominantly negative, it is pathologic. is pathologic.

Quadrant Approach: Example 1Quadrant Approach: Example 1

Negative in I, positive in aVF RAD

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

Quadrant Approach: Example 2Quadrant Approach: Example 2

Positive in I, negative in aVF Predominantly positive in II

Normal Axis (non-pathologic LAD)

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

The Equiphasic ApproachThe Equiphasic Approach

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

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

Step 2: Determine regularityStep 2: Determine regularity

Look at the R-R distances (using a caliper or Look at the R-R distances (using a caliper or markings on a pen or paper).markings on a pen or paper).

Regular (are they equidistant apart)? Regular (are they equidistant apart)? Occasionally irregular? Regularly irregular? Occasionally irregular? Regularly irregular? Irregularly irregular?Irregularly irregular?

Interpretation?Interpretation? Regular

R R

Step 3: Assess the P wavesStep 3: Assess the P waves

Are there P waves?Are there P waves?

Do the P waves all look alike?Do the P waves all look alike?

Do the P waves occur at a regular rate?Do the P waves occur at a regular rate?

Is there one P wave before each QRS?Is there one P wave before each QRS?

Interpretation?Interpretation? Normal P waves with 1 P wave for every QRS

Step 4: Determine PR intervalStep 4: Determine PR interval

Normal: 0.12 - 0.20 seconds.Normal: 0.12 - 0.20 seconds.

(3 - 5 boxes)(3 - 5 boxes)

Interpretation?Interpretation? 0.12 seconds

Step 5: QRS durationStep 5: QRS duration

Normal: 0.04 - 0.12 seconds.Normal: 0.04 - 0.12 seconds.

(1 - 3 boxes)(1 - 3 boxes)

Interpretation?Interpretation?0.08 seconds

Rhythm SummaryRhythm Summary

RateRate 90-95 bpm90-95 bpm

RegularityRegularity regularregular

P wavesP waves normalnormal

PR intervalPR interval 0.12 s0.12 s

QRS durationQRS duration 0.08 s0.08 s

Interpretation?Interpretation?Normal Sinus Rhythm

The QRS Complex with Interval and Segment Measurements

ECG Paper and related Heart Rate & Voltage Computations

Arrhythmia FormationArrhythmia Formation

Arrhythmias can arise from problems in Arrhythmias can arise from problems in the:the:

• Sinus nodeSinus node

• Atrial cellsAtrial cells

• AV junctionAV junction

• Ventricular cellsVentricular cells

SA Node ProblemsSA Node Problems

The SA Node can:The SA Node can:

fire too slowfire too slow

fire too fastfire too fast Sinus BradycardiaSinus Bradycardia

Sinus TachycardiaSinus Tachycardia

Sinus Tachycardia may be an appropriate response to stress.

Atrial Cell ProblemsAtrial Cell Problems

Atrial cells can:Atrial cells can:

fire occasionally fire occasionally from a focus from a focus

fire continuously fire continuously due to a looping re-due to a looping re-entrant circuit entrant circuit

Premature Atrial Premature Atrial Contractions (PACs)Contractions (PACs)

Atrial Flutter Atrial Flutter

AV Junctional ProblemsAV Junctional Problems

The AV junction can:The AV junction can:

fire continuously fire continuously due to a looping due to a looping re-entrant circuit re-entrant circuit

block impulses block impulses coming from the coming from the SA NodeSA Node

Paroxysmal Paroxysmal Supraventricular Supraventricular TachycardiaTachycardia

AV Junctional BlocksAV Junctional Blocks

Rhythm #1Rhythm #1

30 bpm• Rate?• Regularity? regular

normal

0.10 s

• P waves?

• PR interval? 0.12 s• QRS duration?

Interpretation? Sinus Bradycardia

Rhythm #2Rhythm #2

130 bpm• Rate?• Regularity? regular

normal

0.08 s

• P waves?

• PR interval? 0.16 s• QRS duration?

Interpretation? Sinus Tachycardia

Premature BeatsPremature Beats

Premature Atrial ContractionsPremature Atrial Contractions (PACs)(PACs)

Premature Ventricular ContractionsPremature Ventricular Contractions (PVCs)(PVCs)

Rhythm #3Rhythm #3

70 bpm• Rate?• Regularity? occasionally irreg.

2/7 different contour

0.08 s

• P waves?

• PR interval? 0.14 s (except 2/7)• QRS duration?

Interpretation? NSR with Premature Atrial Contractions

Premature Atrial ContractionsPremature Atrial Contractions

Deviation from NSRDeviation from NSR– These ectopic beats originate in the These ectopic beats originate in the

atria (but not in the SA node), therefore atria (but not in the SA node), therefore the contour of the P wave, the PR the contour of the P wave, the PR interval, and the timing are different than interval, and the timing are different than a normally generated pulse from the SA a normally generated pulse from the SA node.node.

Rhythm #4Rhythm #4

60 bpm• Rate?• Regularity? occasionally irreg.

none for 7th QRS

0.08 s (7th wide)

• P waves?

• PR interval? 0.14 s• QRS duration?

Interpretation? Sinus Rhythm with 1 PVC

Ventricular ConductionVentricular Conduction

NormalSignal moves rapidly through the ventricles

AbnormalSignal moves slowly through the ventricles

AV Nodal BlocksAV Nodal Blocks

1st Degree AV Block1st Degree AV Block

2nd Degree AV Block, Type I2nd Degree AV Block, Type I

2nd Degree AV Block, Type II2nd Degree AV Block, Type II

3rd Degree AV Block3rd Degree AV Block

Rhythm #10Rhythm #10

60 bpm• Rate?• Regularity? regular

normal

0.08 s

• P waves?

• PR interval? 0.36 s• QRS duration?

Interpretation? 1st Degree AV Block

1st Degree AV Block1st Degree AV Block

Etiology:Etiology: Prolonged conduction delay in Prolonged conduction delay in the AV node or Bundle of His.the AV node or Bundle of His.

Rhythm #11Rhythm #11

50 bpm• Rate?• Regularity? regularly irregular

nl, but 4th no QRS

0.08 s

• P waves?

• PR interval? lengthens• QRS duration?

Interpretation? 2nd Degree AV Block, Type I

Rhythm #12Rhythm #12

40 bpm• Rate?• Regularity? regular

nl, 2 of 3 no QRS

0.08 s

• P waves?

• PR interval? 0.14 s• QRS duration?

Interpretation? 2nd Degree AV Block, Type II

2nd Degree AV Block, Type II2nd Degree AV Block, Type II

Deviation from NSRDeviation from NSR– Occasional P waves are completely Occasional P waves are completely

blocked (P wave not followed by QRS).blocked (P wave not followed by QRS).

Rhythm #13Rhythm #13

40 bpm• Rate?• Regularity? regular

no relation to QRS

wide (> 0.12 s)

• P waves?

• PR interval? none• QRS duration?

Interpretation? 3rd Degree AV Block

3rd Degree AV Block3rd Degree AV Block

Deviation from NSRDeviation from NSR– The P waves are completely blocked in The P waves are completely blocked in

the AV junction; QRS complexes the AV junction; QRS complexes originate independently from below the originate independently from below the junction.junction.

Supraventricular ArrhythmiasSupraventricular Arrhythmias

Atrial FibrillationAtrial Fibrillation

Atrial FlutterAtrial Flutter

Paroxysmal Supraventricular Paroxysmal Supraventricular TachycardiaTachycardia

Rhythm #5Rhythm #5

100 bpm• Rate?• Regularity? irregularly irregular

none

0.06 s

• P waves?

• PR interval? none• QRS duration?

Interpretation? Atrial Fibrillation

Atrial FibrillationAtrial Fibrillation

Deviation from NSRDeviation from NSR– No organized atrial depolarization, so no No organized atrial depolarization, so no

normal P waves (impulses are not normal P waves (impulses are not originating from the sinus node).originating from the sinus node).

– Atrial activity is chaotic (resulting in an Atrial activity is chaotic (resulting in an irregularly irregular rate).irregularly irregular rate).

– Common, affects 2-4%, up to 5-10% if > Common, affects 2-4%, up to 5-10% if > 80 years old80 years old

Rhythm #6Rhythm #6

70 bpm• Rate?• Regularity? regular

flutter waves

0.06 s

• P waves?

• PR interval? none• QRS duration?

Interpretation? Atrial Flutter

Rhythm #7Rhythm #7

74 148 bpm• Rate?• Regularity? Regular regular

Normal none

0.08 s

• P waves?

• PR interval? 0.16 s none• QRS duration?

Interpretation? Paroxysmal Supraventricular Tachycardia (PSVT)

PSVTPSVT

Deviation from NSRDeviation from NSR– The heart rate suddenly speeds up, The heart rate suddenly speeds up,

often triggered by a PAC (not seen often triggered by a PAC (not seen here) and the P waves are lost.here) and the P waves are lost.

Ventricular ArrhythmiasVentricular Arrhythmias

Ventricular TachycardiaVentricular Tachycardia

Ventricular FibrillationVentricular Fibrillation

Rhythm #8Rhythm #8

160 bpm• Rate?• Regularity? regular

none

wide (> 0.12 sec)

• P waves?

• PR interval? none• QRS duration?

Interpretation? Ventricular Tachycardia

Ventricular TachycardiaVentricular Tachycardia

Deviation from NSRDeviation from NSR– Impulse is originating in the ventricles Impulse is originating in the ventricles

(no P waves, wide QRS).(no P waves, wide QRS).

Rhythm #9Rhythm #9

none• Rate?• Regularity? irregularly irreg.

none

wide, if recognizable

• P waves?

• PR interval? none• QRS duration?

Interpretation? Ventricular Fibrillation

Ventricular FibrillationVentricular Fibrillation

Deviation from NSRDeviation from NSR– Completely abnormal.Completely abnormal.

Diagnosing a MIDiagnosing a MI

To diagnose a myocardial infarction you To diagnose a myocardial infarction you need to go beyond looking at a rhythm need to go beyond looking at a rhythm strip and obtain a 12-Lead ECG.strip and obtain a 12-Lead ECG.

Rhythm Strip

12-Lead ECG

ST ElevationST Elevation

One way to One way to diagnose an diagnose an acute MI is to acute MI is to look for look for elevation of the elevation of the ST segment.ST segment.

ST Elevation (cont)ST Elevation (cont)

Elevation of the Elevation of the ST segment ST segment (greater than 1 (greater than 1 small box) in 2 small box) in 2 leads is leads is consistent with a consistent with a myocardial myocardial infarction.infarction.

Now, where do you think this person is Now, where do you think this person is having a myocardial infarction?having a myocardial infarction?

Inferior Wall MIInferior Wall MI

This is an inferior MI. Note the ST elevation This is an inferior MI. Note the ST elevation in leads II, III and aVF.in leads II, III and aVF.

How about now?How about now?

Anterolateral MIAnterolateral MI

This person’s MI involves This person’s MI involves bothboth the anterior wall the anterior wall (V(V22-V-V44) and the lateral wall (V) and the lateral wall (V55-V-V66, I, and aVL)!, I, and aVL)!

RIGHT ATRIAL ENLARGEMENTRIGHT ATRIAL ENLARGEMENT

Right atrial enlargementRight atrial enlargement – Take a look at this ECG. What do you notice about Take a look at this ECG. What do you notice about

the P waves?the P waves?

The P waves are tall, especially in leads II, III and avF. Ouch! They would hurt to sit on!!

Right atrial enlargementRight atrial enlargement – To diagnose RAE you can use the following criteria:To diagnose RAE you can use the following criteria:

IIII P > 2.5 mmP > 2.5 mm, or, orV1 or V2V1 or V2 P > 1.5 mmP > 1.5 mm

Remember 1 small box in height = 1 mm

A cause of RAE is RVH from pulmonary hypertension.

> 2 ½ boxes (in height)

> 1 ½ boxes (in height)

Left atrial enlargementLeft atrial enlargement – Take a look at this ECG. What do you notice about Take a look at this ECG. What do you notice about

the P waves?the P waves?

The P waves in lead II are notched and in lead V1 they have a deep and wide negative component.

Notched

Negative deflection

Left atrial enlargementLeft atrial enlargement – To diagnose LAE you can use the following criteria:To diagnose LAE you can use the following criteria:

IIII > 0.04 s (1 box) between notched peaks> 0.04 s (1 box) between notched peaks, , ororV1V1 Neg. deflection > 1 box wide x 1 box Neg. deflection > 1 box wide x 1 box deepdeep

Normal LAE

A common cause of LAE is LVH from hypertension.

Left Ventricular HypertrophyLeft Ventricular Hypertrophy

Compare these two 12-lead ECGs. What stands Compare these two 12-lead ECGs. What stands out as different with the second one?out as different with the second one?

Normal Left Ventricular Hypertrophy

Answer: The QRS complexes are very tall (increased voltage)

Left Ventricular HypertrophyLeft Ventricular Hypertrophy

Criteria exists to diagnose LVH using a 12-lead ECG.Criteria exists to diagnose LVH using a 12-lead ECG. – For example:For example:

The R wave in V5 or V6 plus the S wave in V1 or V2 The R wave in V5 or V6 plus the S wave in V1 or V2 exceeds 35 mm.exceeds 35 mm.

Right ventricular hypertrophyRight ventricular hypertrophy– Take a look at this ECG. What do you notice about Take a look at this ECG. What do you notice about

the axis and QRS complexes over the right ventricle the axis and QRS complexes over the right ventricle (V1, V2)?(V1, V2)?

There is right axis deviation (negative in I, positive in II) and there are tall R waves in V1, V2.

Right ventricular hypertrophyRight ventricular hypertrophy – To diagnose RVH you can use the following criteria:To diagnose RVH you can use the following criteria:

Right axis deviationRight axis deviation, and, andV1V1 R wave > 7mm tallR wave > 7mm tall

A common cause of RVH is left heart failure.

Right ventricular hypertrophyRight ventricular hypertrophy– Compare the R waves in V1, V2 from a normal ECG and one Compare the R waves in V1, V2 from a normal ECG and one

from a person with RVH.from a person with RVH.– Notice the R wave is normally small in V1, V2 because the right Notice the R wave is normally small in V1, V2 because the right

ventricle does not have a lot of muscle mass.ventricle does not have a lot of muscle mass.– But in the hypertrophied right ventricle the R wave is tall in V1, But in the hypertrophied right ventricle the R wave is tall in V1,

V2.V2.

Normal RVH

Left ventricular hypertrophyLeft ventricular hypertrophy– Take a look at this ECG. What do you notice about Take a look at this ECG. What do you notice about

the axis and QRS complexes over the left ventricle the axis and QRS complexes over the left ventricle (V5, V6) and right ventricle (V1, V2)?(V5, V6) and right ventricle (V1, V2)?

There is left axis deviation (positive in I, negative in II) and there are tall R waves in V5, V6 and deep S waves in V1, V2.

The deep S waves seen in the leads over the right ventricle are created because the heart is depolarizing left, superior and posterior (away from leads V1, V2).

Left ventricular hypertrophyLeft ventricular hypertrophy– To diagnose LVH you can use the following criteria*:To diagnose LVH you can use the following criteria*:

R in V5 (or V6) + S in V1 (or V2) > R in V5 (or V6) + S in V1 (or V2) > 35 mm35 mm, or, or

avLavL R > 13 mmR > 13 mm

A common cause of LVH is hypertension.

* There are several other criteria for the diagnosis of LVH.

S = 13 mm

R = 25 mm

Bundle Branch BlocksBundle Branch Blocks

So, conduction in the So, conduction in the Bundle Branches and Bundle Branches and Purkinje fibers are Purkinje fibers are seen as the QRS seen as the QRS complex on the ECG.complex on the ECG.

Therefore, a conduction block of the Bundle Branches would be reflected as a change in the QRS complex.

Right BBB

Bundle Branch BlocksBundle Branch Blocks

With Bundle Branch Blocks you will see two changes With Bundle Branch Blocks you will see two changes on the ECG.on the ECG.

1.1. QRS complex widensQRS complex widens (> 0.12 sec) (> 0.12 sec). .

2.2. QRS morphology changesQRS morphology changes (varies depending on ECG lead, (varies depending on ECG lead, and if it is a right vs. left bundle branch block)and if it is a right vs. left bundle branch block)..

Right Bundle Branch BlocksRight Bundle Branch Blocks

What QRS morphology is characteristic?What QRS morphology is characteristic?

V1

For RBBB the wide QRS complex assumes a unique, virtually diagnostic shape in those leads overlying the right ventricle (V1 and V2).

“Rabbit Ears”

RBBBRBBB

Left Bundle Branch BlocksLeft Bundle Branch Blocks

What QRS morphology is characteristic?What QRS morphology is characteristic?

For LBBB the wide QRS complex assumes a characteristic change in shape in those leads opposite the left ventricle (right ventricular leads - V1 and V2).

Broad, deep S waves

Normal

HYPERKALEMIAHYPERKALEMIA

HYPERKALEMIAHYPERKALEMIA

SEVERE HYPERKALEMIASEVERE HYPERKALEMIA

HYPOKALEMIAHYPOKALEMIA

HYPOKALEMIAHYPOKALEMIA

HYPOKALEMIAHYPOKALEMIA

HYPERCALCEMIAHYPERCALCEMIA

HYPOCALCEMIAHYPOCALCEMIA

ACUTE PERICARDITISACUTE PERICARDITIS

ACUTE PERICARDITISACUTE PERICARDITIS

CARDIAC TAMPONADECARDIAC TAMPONADE

PERICARDIAL EFFUSION-PERICARDIAL EFFUSION-Electrical alteransElectrical alterans

HYPOTHERMIA-OSBORNE WAVEHYPOTHERMIA-OSBORNE WAVE

HYPOTHERMIA- HYPOTHERMIA- Giant Osborne waves Giant Osborne waves