Cardinal ECG Features

The cardinal ECG features of AV-nodal re-entrant tachycardias are:

• Always narrow complex (unless pre-existing bundle branch block)
• P wave simultaneous with QRS (see image)

Learning Bite

In nodal re-entry tachycardia ventricular and atrial (retrograde) depolarisation is simultaneous, so the P waves are buried in the QRS complex.