This site is intended for healthcare professionals

Go to /sign-in page

You can view 5 more pages before signing in

Electrocardiography

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

The ECG is an record of the electrical activity of the heart. Its utility stems from the specific changes in the trace caused by various pathologies.

The P waves represent atrial depolarisation. The PR interval is caused by the slow propagation of the depolarisation through the AVN; this allows time for the ventricles to fill. PR is measured from the start of P to the start of R. Once the depolarisation reaches the ventricles, conduction must be fast. The impulse passes though the following hierarchy of structures:

  • AVN then:
    • bundle of His then:
      • right bundle branch
      • left bundle branch then:
        • anterior fascicle of the left bundle branch
        • posterior fascicle of the left bundle branch

Ventricular depolarisation is recorded as the QRS complex. In practice, the Q, R and S waves are not always present.

The Q wave is defined as any initial downward deflection. The R wave is defined as any deflection upwards. The S wave is defined as any down deflection that is not Q. The T wave is the repolarisation.

Teams of Leads Inferior: II, III, aVF Anterior: I, aVL, V1, V2, V3


Related pages

Create an account to add page annotations

Add information to this page that would be handy to have on hand during a consultation, such as a web address or phone number. This information will always be displayed when you visit this page