Cardiology Teaching Package
A Beginners Guide to Normal Heart Function, Sinus Rhythm & Common Cardiac Arrhythmias
The QRS Complex
After the first wave there follows a short period where the line is flat. This is the point at which the stimulus is delayed in the bundle of His to allow the atria enough time to pump all the blood into the ventricles.
As the ventricles fill, the growing pressure causes the valves between the atria and ventricles to close. At this point the electrical stimulus passes from the bundle of His into the bundle branches and Purkinje fibres. The amount of electrical energy generated is recorded as a complex of 3 waves known collectively as the QRS complex. Measuring the waves vertically shows voltage. More voltage is required to cause ventricular contraction and therefore the wave is much bigger.
