2025 ECG Quiz 3 Flashcards
Cardiac Axis, Hypertrophy and Enlargement
Electrical Axis of the Heart
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
Normal Axis
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!!!
Determining Normal Axis Lead I
-90 to 90 degrees: Positive QRS complex in Lead I
Determining Normal Axis aVF
0 to 180 degrees: Positive QRS complex in lead aVF
Determining Normal Axis Lead I and aVF
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
Defining Axis Precisely
Identify a biphasic QRS complex in a limb lead.
Look for an iso-electric biphasic wave.
Axis must be perpendicular to this lead.
Actual ECG of Normal Axis
Positive deflection in Lead I and aVF means normal axis
Abnormal Electrical Axis
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.
Right Axis Deviation
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.
Right Axis Deviation on ECG
Extreme Right Axis Deviation
Northwest Axis or Superior Axis Deviation
Left Axis Deviation
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.
Left Bundle Branch Block Causing Left Axis Deviation
Left Axis Deviation on ECG
Axis Summary
Axis Summary
Axis Summary
Practice ECG
Practice ECG
Hypertrophy vs Enlargement
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
Axis Deviation: Right and Left Ventricular Hypertrophy
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
ECG Changes with Hypertrophy
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.
Normal Atrial Depolarization
Enlargement can be seen in Lead II and V1
Right Atrial Enlargement
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
Right Atrial Enlargement in Leads
Right Atrial Enlargement in 12 Lead
Left Atrial Enlargement
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
Left Atrial Enlargement in Leads
Left Atrial Enlargement on 12 Lead
Right Ventricular Hypertrophy
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)
Right Ventricular Hypertrophy in Leads
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
Right Ventricular Hypertrophy on Wheel
Left Ventricular Hypertrophy (Causes)
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
Left Ventricular Hypertrophy on Leads
Precordial Leads:
S wave in V1 plus R wave in V5 or V6 is > 35mm
Limb leads:
R wave in aVL > 11mm
Left Ventricular Hypertrophy on Wheel
Left Ventricular Hypertrophy Rules
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
Diagnosis of Left Ventricular Hypertrophy
S wave in V1 = 19mm
R wave in V5 = 28mm
19mm + 28mm = 47mm, 47mm > 35mm
Secondary Repolarization Abnormalities of Ventricular Hypertrophy
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
LVH vs RVH
LVH or RVH?
… RVH
Why???
LVH or RVH?
Normal
Why???
Biventricular Hypertrophy
Left side will obscure right side electrical indications
Biventricular Hypertrophy in ECG
Primarily see LV indications
ECG Evaluation Synopsis
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
