CHAMBERS ENLARGEMENT ECG-Interpretation

BY

RAGAB ABDELSALAM(MD)

Prof. of Cardiology

* Work overload : may be described as > Enlargement, > Dilation, or > Hypertrophy. * The term enlargement generally encompasses both dilation and hypertrophy. * Diastolic overload : Increased diastolic volume, referred to as volume overload .

** Chamber dilation as in : valvular regurgitation and CHF & DCM **Cardiac hypertrophy = increase in muscle mass of the myocardium= pressure overload or systolic overload. **Hypertrophy usually as in: > valvular stenosis or hypertension.

** Hypertrophy and dilation frequently occur together, as both are ways in which the heart compensates to maximize cardiac output ** The atria, which are chambers with relatively thin walls, tend to respond to both volume overload and pressure overload by dilating. ** The term enlargement is more inclusive of both dilation and hypertrophy

GENERAL ECG CONSIDERATIONS

* When one evaluates the ECG for evidence of chamber enlargement,

>>Three basic concepts

are helpful in understanding why certain ECG changes occur

1. The chamber

may take longer to depolarize, potentially causing an ECG waveform of prolonged duration.

2. The enlarged

chamber may generate more current than normal, thereby producing greater voltage and an ECG waveform of increased amplitude.

3. A larger percentage

of the total electrical current may move through the expanded chamber, thus shifting the electrical axis of the ECG

* Strain.

* In patients with

LV enlargement, the myocardium may become so enlarged that portions may not receive adequate blood flow.

*

Because CBF

perfuses from epicardium to the endocardium, the myocardium that is most vulnerable to ischemia in patients with LV enlargement is the subendocardium.

•

Subendocardia

l ischemia causes changes in the ST segment and T wave. •

These changes

in the ST segment and the T wave are referred to as the strain pattern.

•

The ECG changes

include depression of the ST segment and inversion of the T wave and are considered to be secondary changes

•

The strain pattern

is most evident in those leads that overlie the enlarged ventricle and will show tall R waves. •

Therefore, RV

strain will be evident in leads V1 and V2, whereas left ventricular strain will be seen in leads I, aVL, V5, and V6.

> The significance

of strain is that it usually indicates severe hypertrophy and may even signify the onset of ventricular dilation

> When true

myocardial ischemia occurs in the presence of LV enlargement, primary changes in the T wave appear as deep, symmetric T wave inversion and will replace the secondary changes in the T wave.

Electrical axis

The sum

of all electrical currents in the heart during systole • * Electrical axis can be evaluated for the P, QRS, and T waves.

* However

, most references refer to the mean QRS axis in the frontal plane,

* Specific

axis determination requires inspection of the six limb leads

•

Electrical axis

is recorded in degrees progressing in a clockwise direction with the positive electrode of lead I, or straight to the patient's left, designated as 0 °.

•

The negative

electrode of lead I , or straight to the patient's right, is +180 °

* The normal mean

QRS axis is directed leftward somewhere between 30 ° and +90°.

* Some sources

expand normal axis to include +120 °

*Abnormal axis

deviations can be seen in conditions such as hemiblocks and chamber enlargement.

* Axis deviations:

Normal axis

:

 0 ° to +90° Left axis

:

 Right axis

:

 Extreme axis

:

 30 ° to 90° >+90 ° to ±180° 90 ° to ±180°

>> P wave

enlargement.

represents atrial depolarization, >> P wave is assessed for evidence of atrial

>> Similarly

, QRS complex is assessed to determine ventricular enlargement.

>> When

the ventricle is enlarged, its corresponding atrium is often enlarged.

>> The presence

of atrial enlargement should therefore trigger the search for evidence of ventricular enlargement

THE NORMAL P WAVE > It represents

the sum of the depolarizations of the R & L atria.

> Because

the SAN is located in the RA , RA depolarization begins slightly before LA depolarization.

> Therefore

blunted apex .

, the initial portion of the P wave primarily reflects RA depolarization, and the terminal portion of the P wave reflects LA depolarization.

P wave usually has a smooth or

•

The normal time

interval for complete atrial depolarization (duration of the P wave) is less than 0.12 seconds. •

Whether the P

wave is +ve or –ve &, it should not exceed 2.5 mm in amplitude. •

P waves

are best seen in II & V1.

•

A vector

is a force such as electric current that has both direction and magnitude. •

Mean P

wave vector reflects the average electrical forces that flow through the atria. This mean P wave vector travels parallel to lead II toward the +ve electrode of that lead.

•

P wave morphology

in lead V1 is often biphasic. •

The P wave in V1 normally

has an initial positive deflection that reflects RA depolarization and is usually less than 1.5 mm in amplitude.

•

The terminal

portion of the P wave in lead V1 has a negative deflection that reflects LA depolarization and normally does not exceed 1 mm in depth .

** P wave usually has

the largest upright deflection in lead II.

*

Changes in P wave morphology may result from : > chamber

enlargement,

> rhythm

disturbances

> abnormalities

in atrial conduction.

*** Therefore

, it has been suggested that the term atrial abnormality be used.

.

ATRIAL ENLARGEMENT

A ) Left Atrial Enlargement The ECG

patterns for LA enlargement may evolve from conditions such as > LA hypertension, > LA hypertrophy, > or impaired interatrial conduction.

** P-mitrale

is a term used to describe a wide and abnormally notched P wave commonly seen in patients who have mitral stenosis and possible

LA

enlargement.

>>

a broad

, notched P wave in leads I & II,

>> slurring

of the terminal portion of the P wave.

>> The distance

between the two peaks of the notched P wave is usually longer than 0.04 s.

>> P duration

is > 0.12 s.

>> The amplitude

is slightly increased.

The term P terminal force: A measurement

of the negative-terminal component of the P wave in lead V1 and is used to help detect enlargement of the left atrium.

It is calculated by multiplying

the depth (in millimeters) of the terminal P wave deflection by its duration (in seconds).

The value is stated in

millimeters per second. A P terminal force greater than 0.03 mm/sec is a sign of left atrial enlargement.

*

A false positive

diagnosis of (COPD

LA

enlargement frequently occurs in patients with ) with or without cor pulmonale

•

In these patients,

a prominent negative P wave can be seen in the right precordial leads without the presence of left-sided heart disease.

>>This may

be due to the anatomic changes that occur in the diaphragm of patients with COPD.

•

Right Atrial Enlargement

The classic causes of RA enlargement are > COPD > Congenital heart disease .( PS Ebstien,s Anomally …) > Pulm. Embolism .

Mechanism of P pulmonale in COLP

:

> Increased

sympathetic stimulation .

> Hyperinflation

of the lungs, which often results in a lowering of the diaphragm and subsequent downward displacement of the heart. This causes the heart to have a more vertical or rightward orientation and clockwise rotation in the chest.

* RA enlargement :

A) P-pulmonale

as in COLD .

; ( P in III > P in II )

B) P-congenitale

: P- in II > P in III ) as in congenital HD >>> PS , …

C) P-tricuspidale

: ( P- wave is tall & notched, with the first peak taller than the second. As in TVD.

D) P-Ebstein

: the tallest P-wave you can see ( usually > ORS in II )

•

Summary of ECG criteria for RA enlargement

> Normal

P wave duration

> Tall, peaked

P waves with an amplitude greater than 2.5 mm in leads II, III, aVF

> Positive

deflection of the P wave in lead V1 or V2 is greater than 1.5 mm

> P wave

axis in the frontal plane leads is +75 ° or greater

•

Clinical Mimics.

•

The P-pulmonale pattern can appear transiently with :

> Acute pulmonary embolism, > Acute bronchial asthma, > Arterial desaturation. > Coronary artery disease, angina pectoris, tachycardia, and exercise.

 Increased sympathetic tone can increase the amplitude of the P wave.  Moreover , the ECG of healthy persons who have a tall, slim build may reveal tall, peaked P waves related to the more vertical position of the heart

• A pseudo P-pulmonale pattern may be seen in patients with LA enlargement due to MV disease • In a pseudo P-pulmonale P-pulmonale.

pattern, as seen in LA enlargement, analyzing lead V1 for the presence of a negative P terminal force may help in the differential diagnosis of true vs pseudo

Biatrial Enlargement

Abnormalities of the two atria affect different components of the P wave, with the ECG pattern manifesting characteristics of both left and right atrial enlargement

Summary of ECG criteria for biatrial abnormality

* Large biphasic P wave in V1 with initial positive portion of the P wave greater than 1.5 mm * terminal negative component up to 1 mm in depth and 0.04 seconds in duration (abnormal P terminal force)

* Tall, peaked P wave

>

1.5 mm in the right precordial leads (V1, V2) and a wide, notched P wave in the limb leads (I, II, III, aVR, aVL, aVF) or left precordial leads (V5 and V6)

* Increase in both

amplitude (2.5 mm or more) and duration (0.12seconds or more) of the P wave in the limb leads

OVERVIEW OF VENTRICULAR PHYSIOLOGY

> The ventricles

consist of the interventricular septum and the free walls of the right and left ventricles.

> The free wall

of the LV is at least three times thicker than that of the RV, and the IVS forms a continuum with the free wall of the LV

•

The Normal QRS Complex

The QRS complex

reflects ventricular depolarization and is inscribed on the ECG after ventricular activation. •

The initial vector

is depolarization of the IVS, which occurs from left to right. This is followed by depolarization of the ventricles. • The impulse is delivered to the subendocardium of both ventricles at about the same time, resulting in an almost simultaneous depolarization.

>The normal

QRS duration is 0.06 to 0.10 seconds.

 The amplitude of a QRS is influenced by the thickness of the muscle mass involved.

 The net wave of ventricular depolarization, known as the mean QRS vector, is directed inferiorly and to the left .

> The QRS

will be predominantly upright in leads I, II, III, aVL, aVF, V4, V5, and V6.

> Normally,

a progressive increment in the amplitude of the R wave occurs from leads V1 through V6 while small q waves begin to appear from leads V4 through V6.

•

The R wave

begins as a small (<7 mm) upright waveform in lead V1 and becomes progressively taller across the left precordia leads. •

In addition

, the S wave is deep in lead V1 and becomes progressively smaller across the left precordial leads

•

Leads I, aVL

, or V6 will show a small initial q wave, representing the mean septal vector traveling away from the +ve electrode of these leads. •

This q wave

is followed by a relatively tall R wave, which represents the mean QRS vector traveling through the LV toward the +ve electrodes.

• •

> In V1 and V2

, the mean septal vector is directed towards these +ve electrodes, inscribing a small r wave.

> This is followed

by a relatively deep S wave, which results from the mean QRS vector traveling through the LV away from the positive electrodes

> The intrinsicoid

deflection is a term used to represent ventricular activation time or the time required for peak voltage to develop.

> >

It is measured

from the onset of the QRS complex to the peak of the R wave.



The two leads

assess ventricular activation time are V1 and V6.

that are used to 

Activation

of the RV usually occurs first, lasts approximately 0.02 Seconds, and is best seen in lead V1.

> Activation

approximately 0.04 seconds and is best seen in lead V6 of the left ventricle lasts

VENTRICULAR ENLARGEMENT

Left Ventricular Enlargement * CHF and MR

are examples of conditions that may cause volume overload,

* pressure

overload may result from such conditions as AS or systemic hypertension.

* Aging

, diabetes mellitus, and cardiomyopathy are examples of neurohumoral factors leading to enlargement of the left ventricle.

• • • •

ECG Characteristics of LV Enlargement

.

When the LV

increased.

enlarges, the normal sequence of ventricular depolarization is retained, but the electrical dominance of the LV over the RV is

In patients with LV

leads .

enlargement, the mean QRS vector travels more posteriorly and leftward, increasing ventricular activation time (intrinsicoid deflection) and voltage (amplitude) in certain

Secondary

abnormalities in the ST-T segments are common in the later stages of LV enlargement and are referred to as "strain,"

•

Many complex

criteria are used to diagnose LV enlargement with the 12 lead ECG

.

•

> It should be remembered

that ECG changes associated with LV enlargement occur primarily in the QRS complex and that these criteria for diagnosing LV enlargement reflect two common themes :

• •

(1) increased

amplitude of the R wave in leads overlying the LV.

(2) increased

amplitude of the S wave in leads overlying the RV.

•

Usually, the

precordial leads are more sensitive indicators than the limb leads are for the diagnosis of left ventricular enlargement .

•

The more criteria

present, the more likely the patient has enlargement of the LV. •

wave amplitude

in lead V5 or V6 plus the S wave amplitude in lead V1 or V2 exceeding 35 mm) is often considered the most accurate.

•

The precordial

lead criteria are of less value in persons less than 35 years old •

the first criterion

listed for limb leads (R wave amplitude in lead aVL exceeding 13 mm) is probably the most useful.

•

Both right and left

ventricular enlargement may slightly prolong the QRS duration, but rarely beyond 0.10 seconds.

•

The diagnostic

accuracy of ECG for LV enlargement is improved when :

•

ST- depression and T wave

inversion accompany the aforementioned voltage criteria (referred to as the strain pattern).

•

Additional ECG clues

for detecting LV enlargement are LA enlargement, delayed onset of intrinsicoid deflection (>0.045 seconds), and deviation of the axis to the left.

Diagnostic ECG criteria of LV enlargement

> Precordial leads

•

The R wave

amplitude in lead V5 or V6 plus the S wave amplitude in lead V1 or V2 is greater than 35 mm • The R wave amplitude in lead V5 is greater than 26 mm • The R wave amplitude in lead V6 is greater than 18 mm • The R wave amplitude in lead V6 is greater than the R wave amplitude in lead V5

Limb leads

> The R

wave in lead aVL is > 13 mm

> The R

wave in lead aVF is > 21 mm

> The R

wave in lead I is > 14 mm

>The R

wave in lead I plus the S wave amplitude in lead III is > 25 mm

Scott,s Criteria

Limb leads:

* R in 1 + S in 3: > 25 mm * R in aVL : > 7.5 mm * R in aVF; > 20mm * S in aVR: > 14 mm

Chest leads :

*

S in V1,or 2 + R in V5,or 6: >35 mm * R in V5 or V6 : > 26 mm * R + S in any V lead: > 45 mm

Estes, Scoring system for LVH

1-R or S in limb lead : 20 mm or more S in V1,2 or 3 25 mm or more R in V4 ,5, 0r 6 25 mm or mor e --------------------------------------------------------- 2-Any St-segment shift: > with digitalis > without digitalis --------------------------------------------------------- 3 – LAD -15 degree or more --------------------------------------------------------- 4 – I.D in V5, 6 0.04 or more

3

---------- 3 1 ---------- 2 -------- 1

5- QRS duration : 0.09 sec or more

1

6- P-terminal force in V1 > 0.04

--------------------------------------------------------

3

-------------

TOTAL

================================

5 or more= LVH 4 = probable

13

=======

*Cornell criteria:

- R wave

in aVL + S wave in V3 > 24 mm

- Downsloping

of ST-depression & asymmetric T wave inversion

- Prominent

U waves

Systolic Vs Diastolic

Overload

*In systolic overload

> the criteria

of LV strain are evident: - St-segment depression - T-wave inversion - U-wave inversion in left precordial leads.

* In diastolic Overload:

- R- wave is markedly increased - T-wave is upright , large & pointed .

Clinical Mimics:



Age

, body build, sex, and race can produce ECG changes that mimic those of left ventricular enlargement. 

Adolescents

and young adults may have taller QRS complexes.



Men tend

to have a greater QRS amplitude than do women.



Blacks

have a taller QRS voltage than their white counterparts.

> Body build can

either mimic or mask left ventricular enlargement. > In thin or emaciated persons, the QRS amplitude tends to be greater, causing LV enlargement to be overdiagnosed, whereas in obese people, LV enlargement can be underdiagnosed because of decreased QRS voltage from the insulating effects of fat.

> In addition

, fever, anemia, thyrotoxicosis, and other high COP states can increase QRS voltage without corresponding LV enlargement.

Right Ventricular Enlargement

> Normally,

the left ventricle is anatomically and electrophysiologically the dominant ventricle

> However

, any condition that causes an overload of the RV may lead to RV enlargement.

> Examples

include pulmonary disease and congenital or acquired heart disease.

> Normally

, the mean right ventricular vector travels in an anterior and rightward direction but is usually overshadowed by the dominant left ventricle .

•

Because

of the anatomic differences between the RV and LV, slight enlargement of the RV usually does not produce significant ECG abnormalities. •

With increasing

enlargement of the RV , the RV mass may equal and may eventually dominate theelectrical effects of the LV

** ECG Characteristics of RV Enlargement

.

> The earliest

enlargement is a progressive deviation of the axis to the right. manifestation of RV

> RAD seen

in the limb leads is the essential criterion in diagnosing RV enlargement.

> RAD that

exceeds +100 ° significant for RV enlargement.

is considered

> In lead I,

RAD is manifested by a QRS complex that is more negative than positive

•

A second ECG

manifestation is a progressive decrease in the depth of the S wave in V1.

•

Because lead V1

is closer to the RV it is a more sensitive lead to the changes of RV enlargement.

•

In cases

of RV enlargement, the S wave will be initially small in lead V1 and become progressively deeper toward lead V6 •

Simultaneously

, the normal pattern of R wave progression is interrupted

•

In patients with RV

enlargement, the R wave in lead V1 is initially large (>7 mm) and becomes progressively smaller toward lead V6. •

RV enlargement

may also result in a delayed intrinsicoid deflection of more than 0.035 seconds in the right precordial leads (V1 and V2)

•

One of the most

specific ECG signs in patients with a severe degree of right ventricular enlargement and hypertrophy is a qR wave seen in lead V1. •

The reason

for this qR wave is not fully understood; however, it is believed to result from the initial septal vectors being altered because of the increased muscle mass of the septum

•

Additional criteria

for RV enlargement include ST-T wave abnormalities representing ventricular strain.

>> The ECG

strain includes pattern for RV ventricular • ST depression • T wave inversion in leads V1, V2, II, III, and aVF.

summary of ECG diagnostic criteria for RV enlargement

1

-

RAD

of 100 ° or more in the limb leads ( essential criteria ).

2- R

in lead V1 greater than

S .

3- S

in lead V6 greater than

R .

4 Delayed intrinsicoid

deflection in lead V1 greater than 0.035 seconds.

5 - Secondary

ST-T wave

changes in leads V1, V2,, II, III, aVF.

6 - RA

enlargement.

7 - qR

in lead V1 (severe RV enlargement).

Systolic Vs Diastolic

•

Overload

RV-Systolic overload

-Markedly tall R in V!

- right precordial leads strain - rS pattern in lead V6

* RV – Diastolic Overload

- pattern of incomplete or complete RBBB.

NB.

1- S1,S2,S3

index of RV Enlargement in children pattern is a reliable

2- rS pattern

emphysema.

all across the precordial leads is an index of RV enlargement in many cases of

> This pattern

wise rotation ) or poor r-wave progression. is termed (clock-

3-The pattern of rSR

’ in V1 plus AF is an indication of Mitral stenosis with PH

4-pattern of rSr ’

plus left axis deviatin in a patient with ASD indicates Premium defect or ASD+ MVP.

•

Clinical Mimics.

A variety of other clinical conditions may produce ECG findings suggestive of RV enlargement when the condition does not exist.

> RAD

block.

may be due to left posterior fascicular

>

,

ECG changes

enlargement.

associated with inferior, posterior, and high-lateral-wall myocardial infarctions may mimic those of RV

> WPW syndrome

result .

, type A and right bundle branch block may also produce a false-positive

• The

ECG manifestation

of RV enlargement may be a normal variant in some adults, as persons who are tall and slender tend to have:

>

a vertical heart

that can 

produce

findings false-positive for

RV

enlargement.

•

Biventricular Enlargement

** Diagnosis

of biventricular enlargement can be confusing.

> The increased

electrical forces of both ventricles may actually negate each other, producing an ECG that appears normal in amplitude.

>The ECG findings

will be influenced by the degree of enlargement of each of the ventricles.

•

ECG Manifestations of Biventricular Enlargement.

> In patients

with biventricular enlargement, the 12-lead ECG will show features that are a combination of both R and L ventricular enlargement.

> A variety of ECG

clues are suggestive of biven tricular enlargement; however, the best criterion is the pattern of LA enlargement (corresponding to LV enlargement) along with evidence of RV enlargement

* Katz-Watchel phenomenon

.

> The transitional zone : V3, V4.

> The deflections are biphasic & equal .

> R + S > 45 mm > It is characteristically evident in VSD

* Shallow “ S “ Syndrome

> Shallow S in V1



Plus Strikingly deeper S in V2 .

Summary of ECG diagnostic criteria for biventricular enlargement: > Left

artrial enlargement

> S

greater than or equal to R in lead V5 or lead V6

> S

in lead V5 or lead V6 =7 mm or more

> Right

axis deviation of greaer than 100 ° in the limb leads.

* The differential diagnosis of prominent U waves includes all the following except

: 1- Hypokalemia .

2-Hyperkalemia.

3-Digitalis effect 4-Amiodarone.

5-Central nervous system disorders.

6-Left ventricular hypertrophy.

*Anatomical LVH is more likely when Repolarization abnormalities are added to voltage criteria :

> False or > True

Repolarization changes associated with LVH:

1-ST segment & T wave deviation in (

same

of QRS.

/

opposite

) direction to deflection 2-ST segment (

elevation

/

depression

) in I , aVL ,III, aVF and / or V4-V6.

3- < 1-2 mm ST segment (

elevation

/

depression

) in V1-V3.

4-Inverted ---- waves in leads I , aVL, V4-V6. 5- (

Absent

/

prominent

) U waves.

* Factors reduce the sensitivity of voltage criteria diagnostic of LVH include all the following except:

1-Obesity 2- Thin body habitus 3-Severe COPL 4-Pleural or peric. eff.

5-CAD 6- Pneumothorax 7-Infiltrative HD 8-Severe RVH 9-LBBB 10-LA Fascicular Block.

* Causes of RSR ” complex in V1 may include

: 1-RVH.

2- Posterior MI.

3- WPW syndrome.

4-RBBB.

>> The associated ECG findings can help in differential diagnosis

* Match each cause to associated findings in the followings

: A. Right Axis Deviation. B. Inferior MI.

C. RA abnormality.

D. Upright T waves in v1-v3, E. T wave inversion in v1-v3.

F. ORS duration > 0.12 s.

G. Short PR interval.