The ECG leads

What's the difference between positive, negative and isodiphasic waves?


A positive wave is any wave that goes predominantly upwards.

A negative wave is any wave that goes predominantly downwards.

An isodiphasic wave is one in which the wave area upwards is equal to the wave area downwards.

The coronal plane is divided into two types of leads.

bipolar leads, also called standard or classic.

3 augmented peripheral leads.

These 6 leads allow us to observe the heart in the coronal plane in 360°.



Bipolar Peripheral Leads: forming Einthoven's triangle

What are bipolar leads?

Lead D1:

the positive (exploring) electrode is on the left arm and the negative electrode is on the right arm.

So a depolarization wave going from right to left will be captured and will form a positive wave on the ECG.

Lead D2

The positive electrode will be on the left foot and the negative electrode on the right hand.

Lead D3

The positive electrode will be on the left foot and the negative electrode on the left hand.

To memorize this:

just remember that the right hand will always be negative and the left foot will always be positive.

Bipolar leads, when grouped, form an equilateral triangle (known as Einthoven's triangle).

The center of the triangle corresponds to the electrical center of the origin of the vectors (heart).

You live in the center of my Einthoven's triangle = you live in my heart.


Augmented peripheral leads.

The augmented peripheral leads theoretically only have one electrode, the exploring one.

What are the 3 peripheral leads?

aVL: The positive electrode is on the left arm. 

Augmented peripheral leads.

aVR: the exploring electrode will be on the right arm.


Augmented peripheral leads.

aVF: the positive electrode is on the foot. The vector that points downwards will be positive.

Interesting facts about augmented leads

Why are these leads called augmented?

Because they need an amplification in the voltage to be seen in the ECG tracing.

Why is this needed?

Because the complexes recorded would be too small to be of use.


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