The ECG of third degree AV block is characterised by atrial separation and has different types of presentation depending on the severity of the disease and the form of the lesion, as described below.
Firstly, in the ECG of third degree AV block, the atria and ventricles are each excited, with complete atrial separation and no correlation, and the P waves are completely unrelated to the QRS waves.
Secondly, a variety of abnormalities in the atrial rhythm can be seen, commonly sinus rhythm, atrial tachycardia, atrial fibrillation and atrial flutter.
Thirdly, the ventricular rhythm in patients with third degree AV block can be either atrioventricular junctional fugitive rhythm or ventricular fugitive rhythm, which is more regular and slow, 40-60 beats/min and 20-40 beats/min respectively.
Fourth, the atrial rate is more often faster than the ventricular rate and the P wave is faster than the QRS wave in patients with third-degree AV block.