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Cardiology Teaching Package

A Beginners Guide to Normal Heart Function, Sinus Rhythm & Common Cardiac Arrhythmias

The Q Wave

The picture below shows a small negative wave immediately before the large QRS complex. This is known as a Q wave and represents depolarisation in the septum.

Whilst the electrical stimulus passes through the bundle of His, and before it separates down the two bundle branches, it starts to depolarise the septum from left to right. This is only a small amount of conduction (hence the Q wave is less than 2 small squares), and it travels in the opposite direction to the main conduction (right to left) so the Q wave points in the opposite direction to the large QRS complex.

Image: Q Wave

Diagram of the Q wave section of the sinus wave
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