ECG #2 Flashcards
What is the axis of the heart?
Axis is the average direction of electrical activity as it travels through the heart
Typically, we look at the ventricular axis
It changes as the electrical impulse moves through different structures of the heart
Measured in the frontal plane, because that is how the leads are set up
What leads do we use for the Quadrant approach to the heart axis?
Lead 1 and Lead aVF
If lead 1 is positive = shade in the right
If lead 1 is negative = shade in the left
If lead aVF is positive = shade in bottom
If lead aVF is negative = shade in top
Use lead 1 to determine if AP is moving left or right
Use lead aVF to determine if AP is moving up or down
Whichever quadrant overlaps, is the direction of the axis
What is the normal axis?
Normal axis = -30 degrees to +90 degrees
If the axis falls anywhere else, it is deviation
How can we “define” the normal axis?
If we combine lead 1 and lead 2, we get an overlapping area that is defined as the “normal axis”
How do we define Left Axis Deviation (LAD)?
Positive lead 1 and negative lead 2, the overlap is LAD
How do we define Right Axis Deviation (RAD)?
Negative in lead 1 and positive in lead aVF, overlap is RAD
What are isoelectric leads?
Add answer!
Do the online practice lesson.
How do we diagnose a bundle branch block?
Diagnosis made using V1 and V6 (precordial leads)
How do we diagnose a LBBB?
Left bundle doesn’t work. Therefore, the signal will NOT travel down to the LV, and the LV is not depolarized normally. But the RV will be normally depolarized.
- Early fast depolarization of the RV occurs first, causing a small, initial upward signal in V1 (toward the V1)
- Slow late LV depolarization (not using the conducting fibers) (mostly toward V6), producing a WIDE QRS in V6 (3 little squares)
- Repolarization occurs normally, from outside of ventricles into the ventricle. Normal T waves are “concordant” with the QRS, but in LBBB, normal repolarization of LV is lost. Instead follows same pattern as depolarization, causing inverted T waves - opposite the QRS
What do the T waves look like in LBBB?
Because repolarization follows the same path as depolarization, the T waves are non-concordant with QRS, they are OPPOSITE to teh direction of QRS inflection.
What are the 4 diagnostic findings associated with LBBB?
- Wide QRS > 0.12 sec (3 little squares)
- V6: broad upgoing R wave
- V1: small R wave, big S wave (rS)
- QRS and T waves are discordant (opposite inflection)
What happens to the ST segment with LBBB?
Both the QRS and T waves are abnormal in LBBB. Thus, the ST segment is affected as a corollary.
This is important to know because ST segment changes occur with ischemia or MI.
Therefore, when you have LBBB the ST segment is NOT useful for ischemia diagnosis.
What is a Right Bundle Branch Block?
RBBB is when the right bundle does not work. therefore the signal will NOT travel down to the RV in the normal way.
However, the left bundle still works well.
What are the steps of a RBBB and their findings on ECG?
- Early fast depolarization of the septum, causing upgoing V1 and downgoing V6 wave
- Depolarization of LV causes downgoing V1 and upgoing V6, which occurs very quickly
- Depolarization of the RV occurs very slowly and toward V1, causing wider upgoing deflection in V1, wide downgoing deflection in V6
What diagnostic findings are associated with RBBB?
- Wide QRS > 0.12 sec
- RSR’ pattern in V1
- Wide, slurred S wave in V6
- RABBIT ears occur in RBBB
Only similarity between LBBB and RBBB is that the QRS or RSR’ are BOTH wide.
