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NSU AA Denver > 2025 ECG Quiz 3 > Flashcards

2025 ECG Quiz 3 Flashcards

Cardiac Axis, Hypertrophy and Enlargement

1
Q

Electrical Axis of the Heart

A

The axis is in reference to the electrical activity of the QRS complex (ventricular depolarization)

Axis: orientation of the mean electrical vector

First vector: septal depolarization

Late vectors: progression of ventricular depolarization

Mean vector: average vector of all instantaneous vectors

Mean electrical axis: direction of mean vector

Mean QRS vector: usually points left and inferiorly

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2
Q

Normal Axis

A

If the QRS complex axis lies within the shaded quadrant shown here, it is normal.

If the QRS complex is (+) in leads I and aVF, the QRS axis must be normal.

0-90+ = normal

Some cardiologists say -30 works for normal… NOT FOR US!!!

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3
Q

Determining Normal Axis Lead I

A

-90 to 90 degrees: Positive QRS complex in Lead I

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4
Q

Determining Normal Axis aVF

A

0 to 180 degrees: Positive QRS complex in lead aVF

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5
Q

Determining Normal Axis Lead I and aVF

A

If the QRS complex is positive in both leads I and aVF, the QRS axis is normal.

If the QRS complex in either lead I or aVF is not positive, the QRS axis is not normal

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6
Q

Defining Axis Precisely

A

Identify a biphasic QRS complex in a limb lead.

Look for an iso-electric biphasic wave.

Axis must be perpendicular to this lead.

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7
Q

Actual ECG of Normal Axis

A

Positive deflection in Lead I and aVF means normal axis

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8
Q

Abnormal Electrical Axis

A

Rule of thumb: the heart axis rotates towards hypertrophy and away from infarction

Direction of vector changes under various circumstances:
Rotation: the heart itself is rotated. (ex. Right ventricular overload)

Hypertrophy: axis will deviate towards the greater electrical activity. (increased electrical activity)

Infarction: Myocardial tissue is electrically dead. QRS vector turns away from this tissue.

Conduction abnormalities: influence mean electrical vector. Right Bundle Branch Block can shift it.

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9
Q

Right Axis Deviation

A

Right ventricular hypertrophy

Old lateral STEMI

Posterior fascicular block

Electrical axis is between +90 and 180 degrees

If the QRS is predominantly negative in lead I and positive in lead aVF, then the axis is deviated to the right.

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10
Q

Right Axis Deviation on ECG

A
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11
Q

Extreme Right Axis Deviation

A

Northwest Axis or Superior Axis Deviation

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12
Q

Left Axis Deviation

A

Left ventricular hypertrophy

Old inferior STEMI

Left bundle branch block (LBBB) Anterior fascicular block

Electrical axis is between -90 and 0 degrees.

If the QRS is predominantly positive in lead I and negative in lead aVF, then the axis is left and upwards.

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13
Q

Left Bundle Branch Block Causing Left Axis Deviation

A
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14
Q

Left Axis Deviation on ECG

A
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15
Q

Axis Summary

A
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16
Q

Axis Summary

A
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17
Q

Axis Summary

A
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18
Q

Practice ECG

A
19
Q

Practice ECG

A
20
Q

Hypertrophy vs Enlargement

A

HYPERTROPHY:
Increase in myocardial muscle mass.

Result of chronic pressure overload

Heart must pump harder to overcome increased resistance

Think: Pressure and Stenosis of Valve(s) and Hypertension

Increase in size requires more O2 for activity, and makes it harder for vessels to perfuse the tissue (arteries and veins)

ENLARGEMENT:
Dilation of a heart chamber w/out more muscle mass

Result of chronic volume overload

Chamber dilates to accommodate more blood volume

Think: volume overload, insufficient valves/regurgitation

ECG is not good distinguishing between the two

21
Q

Axis Deviation Right and Left Ventricular Hypertrophy

A

Left ventricular hypertrophy:
Leads to left axis deviation
LV increases dominance of mean vector over the RV
Chronic hypertension:
Heart must work harder to overcome increased pressure
LV hypertrophies
Increases dominance of mean vectors

Right ventricular hypertrophy:
Leads to right axis deviation
Uncommon, requiring significant changes in the RV
Can occur in patients with severe COPD or uncorrected congenital heart disease

22
Q

ECG Changes with Hypertrophy

A

Increase in duration:
Chamber takes longer to depolarize

Increase in amplitude:
Chamber generates more electrical current/voltage. The typical indication

Shifts in electrical axis:
Larger percentage of total electrical current can move through the expanded chamber.

23
Q

Normal Atrial Depolarization

A

Enlargement can be seen in Lead II and V1

24
Q

Right Atrial Enlargement

A

Tall, peaked P waves in inferior leads and V1

Indications of right atrial enlargement (RAE)
Amplitude of >2.5mm
No change in duration

P pulmonale
Caused by increased right sided pressures, i.e. pulmonary hypertension or pulmonary valve stenosis

25
Q

Right Atrial Enlargement in Leads

A
26
Q

Right Atrial Enlargement in 12 Lead

A
27
Q

Left Atrial Enlargement

A

Wide, notched P wave in leads I and II, as well as a wide biphasic P wave in V1

Indications of left atrial enlargement (LAE)
Increased amplitude of terminal component of P wave
> 1mm below isoelectric line in lead V1
Duration of terminal component of P wave is increased
> 1 one small square or 0.04 seconds
No significant axis deviation

P mitrale
Caused by increased left sided pressures, i.e. mitral valve stenosis TYPICAL Cause, mitral valve regurgitation, or systemic hypertension

28
Q

Left Atrial Enlargement in Leads

A
29
Q

Left Atrial Enlargement on 12 Lead

A
30
Q

Right Ventricular Hypertrophy

A

Common diagnostic criteria:
Increased R wave amplitude in right ventricle leads
Increased S wave amplitude in left ventricle leads

Common causes:
Severe or chronic pulmonary disease (COPD)
Pulmonary hypertension
Congenital disease
Tetralogy of Fallot
Pulmonary valve stenosis
Ventral septal defect (VSD)

31
Q

Right Ventricular Hypertrophy in Leads

A

Precordial leads:
R wave larger than S wave in V1
S wave larger than R wave in V5-V6

Limb leads:
Right axis deviation, QRS axis > +100 degrees
Predominantly negative QRS in Lead I

32
Q

Right Ventricular Hypertrophy on Wheel

A
33
Q

Left Ventricular Hypertrophy (Causes)

A

Common diagnostic criteria:
Increased R wave amplitude in left ventricle leads
Increased S wave amplitude in right ventricle leads

Common causes:
Systemic hypertension
Aortic stenosis
Athleticism

34
Q

Left Ventricular Hypertrophy on Leads

A

Precordial Leads:
S wave in V1 plus R wave in V5 or V6 is > 35mm

Limb leads:
R wave in aVL > 11mm

35
Q

Left Ventricular Hypertrophy on Wheel

A
36
Q

Left Ventricular Hypertrophy Rules

A

Precordial Lead Rules: BIGGER INDICATOR
The R-Wave amplitude in lead V5 or V6 PLUS the S wave amplitude in lead V1 or V2 exceeds 35 mm
The R-wave amplitude in lead V5 exceeds 26 mm
The R-wave amplitude in lead V6 exceeds 20 mm
The R-wave amplitude in lead V6 exceeds the R-wave amplitude in lead V5

Limb Lead Rules:
R-wave amplitude in aVL is > 11 mm
R-wave amplitude in aVF is > 20 mm
The R-wave amplitude in lead I > 13 mm
The R-wave amplitude in lead I PLUS the S-wave amplitude in lead III > 25 mm

COMBINED: R-wave amplitude in aVL plus the S-wave amplitude in V3 is > 20 (women) and > 28 in men

37
Q

Diagnosis of Left Ventricular Hypertrophy

A

S wave in V1 = 19mm
R wave in V5 = 28mm
19mm + 28mm = 47mm, 47mm > 35mm

38
Q

Secondary Repolarization Abnormalities of Ventricular Hypertrophy

A

Downward sloping ST segment depression

T wave inversion
Resulting from a change in axis so that it no longer closely aligns with the QRS axis

Blends together to form a single asymmetric wave
The downward slope is gradual
The upward slope is sharp

39
Q

LVH vs RVH

A
40
Q

LVH or RVH?

A

… RVH
Why???

41
Q

LVH or RVH?

A

Normal
Why???

42
Q

Biventricular Hypertrophy

A

Left side will obscure right side electrical indications

43
Q

Biventricular Hypertrophy in ECG

A

Primarily see LV indications

44
Q

ECG Evaluation Synopsis

A

Look at ECG
Look at Lead 1 and aVF for axis deviation
Deviation to the left = look for hypertrophy indicators (V5orV6 and V1orV2 adding to over 35mm)
Deviation to the right = look for hypertrophy indicators (V1 and V5-V6)
See nothing (on possible ventricular hypertrophy and/or initial axis deviation evaluation), look to II and V1 for atrium issues in P waves

Right Atrium
Enlargement Causes:
Right sided pressure
Pulmonary hypertension
Pulmonary valve stenosis
Enlargement ECG:
Tall P waves in inferior leads (Lead II particular) and V1 tall P wave with some biphasic action

Left Atrium
Enlargement Causes:
Left sided pressure increase
Mitral valve stenosis
Mitral Valve regurgitation or system hypertension (Typical)
Enlargement ECG:
Lead II shows P waves notched mountain peak and V1 shows hill with valley

Right Ventricular
Hypertrophy Causes:
COPD
Pulmonary Hypertension
Congenital Disease
Tetralogy of Fallot
Pulmonary Valve Stenosis
Ventral Septal Defect
Hypertrophy ECG:
R-Wave larger than S-Wave in V1
S-Wave larger than R-Wave in V5-V6
Lead I biphasic with Lead aVF elevated R-Wave

Left Ventricular
Hypertrophy Causes:
Systemic Hypertension
Aortic Stenosis
Athleticism
Hypertrophy ECG:
R-Wave amplitude in V5 or V6 and S-Wave amplitude in V1or V2 greater than 35mm
R-Wave amplitude in V5 greater than 26mm
R-Wave amplitude in V6 greater than 20mm
R-Wave amplitude in V6 greater than in lead V5
R-Wave in aVL greater than 11mm
T Wave Inversion

NSU AA Denver (15 decks)

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