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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.
• Subendocardial 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°
 30° to 90°
Right axis:
 >+90° to ±180°
Extreme axis:  90° to ±180°
Left axis:
>> P wave represents atrial
depolarization, >> P wave is
assessed for evidence of atrial
enlargement.
>> 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, 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
blunted apex.
• 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 LA
enlargement frequently
occurs in patients with
(COPD) 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 Ppulmonale 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 ; ( P in III > P in II )
as in COLD .
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 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
P-pulmonale.
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 that are used to
assess ventricular activation time are
V1 and V6.
 Activation of the RV usually occurs
first, lasts approximately 0.02 Seconds,
and is best seen in lead V1.
> Activation of the left ventricle lasts
approximately 0.04 seconds and is best
seen
in lead V6
RICULAR
GEMENT
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 enlarges, the normal sequence
of ventricular depolarization is retained, but the
electrical dominance of the LV over the RV is
increased.
• In patients with LV enlargement, the mean
QRS vector travels more posteriorly and leftward,
increasing ventricular activation time (intrinsicoid
deflection) and voltage (amplitude) in certain
leads .
• 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 12lead 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:
* R in aVL :
* R in aVF;
* S in aVR:
> 25 mm
> 7.5 mm
> 20mm
> 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 manifestation of RV
enlargement is a progressive deviation of the
axis to the right.
> RAD seen in the limb leads is the
essential criterion in diagnosing RV enlargement.
> RAD that exceeds +100° is considered
significant for RV enlargement.
> 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 pattern for RV ventricular
strain includes
• 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 pattern is a reliable
index of RV Enlargement in
children
2- rS pattern all across the
precordial leads is an index of RV
enlargement in many cases of
emphysema.
> This pattern is termed (clockwise rotation ) or poor r-wave
progression.
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 may be due to left posterior fascicular
block.
>, ECG changes associated with inferior,
posterior, and high-lateral-wall myocardial
infarctions may mimic those of RV
enlargement.
> WPW syndrome, type A and right bundle
branch block may also produce a false-positive
result .
• 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 biventricular 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 / opposite ) direction to deflection
of QRS.
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
3-Severe COPL
5-CAD
7-Infiltrative HD
9-LBBB
2- Thin body habitus
4-Pleural or peric. eff.
6- Pneumothorax
8-Severe RVH
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.