CHAMBERS ENLARGEMENTECG-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 ECGwaveform of increased amplitude.

3. A larger percentage of the total electrical current may move through the expanded chamber, thus shifting the electricalaxis 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°

Left axis: 30° to 90°

Right axis: >+90° to ±180°

Extreme axis: 90° to ±180°

>>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 suggestedthat 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 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 ; ( 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 ofthe 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

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 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 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

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

Estes, Scoring system for LVH

5- QRS duration : 0.09 sec or more 1

6- P-terminal force in V1 > 0.04

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

TOTAL

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

5 or more= LVH

4 = probable

3

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

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 conditionthat 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 andrightward 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 ECGabnormalities.

• 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 (clock-wise 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 aretall 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 V1Plus Strikingly deeper

S in V2 .

Summary of ECG diagnostic Summary of ECG diagnostic criteria for biventricular criteria for biventricular enlargement:enlargement:

>> Left Left artrial enlargement artrial enlargement

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

> S> S in lead V5 or lead V6 =7 mm or more in lead V5 or lead V6 =7 mm or more

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