# ECG and Vector Analysis

A collapse of Einthoven’s triangle such that the lead lines meet at a single point gives rise to the triaxial lead system
What is the triaxial lead system?
Positive = The labeled end
Negative = Reference end
What are the positive and negative ends of leads called?
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With their origins at the center of the lead system.
I = Left arm
2 = Left leg
3 = Right arm
How are cardiac vectors positioned in the Triaxial lead system?
I + III = II
What is Einthoven’s law?
The mean axis of all electrical vectors in the frontal plane; the normal mean vector of the QRS complex in the frontal plane is between -30 degrees and +90 degrees
What is the mean electrical vector in the frontal plane?
Between -30 and + 90 degrees
An example of a normal axis
Outside of the -30 to +90 degree range
An example of axis deviation
The vector will be shifted right.
How is a vector shifted if there is a conduction delay in the right ventricle?
It uses augmented (unipolar) limb leads.

• aVR = RA(+) @ -150, LA and LL(-)
• aVL = LA(+) @ -30, RA and LL(-)
• aVF = LL(+) @ +90, RA and LA(-)

What is the hexaxial lead system?
Describe the electrode placement.
The lead with zero NET voltage is identified.
The mean vector is then perpendicular to the lead with zero net voltage.
What is the null method?
How is the direction of a vector determined with it?
A lead with zero NET voltage.