Final answer:
AV blocks are categorized into first-degree, second-degree, and third-degree blocks. Each type has distinct characteristics and can be recognized on an ECG.
Step-by-step explanation:
An AV block refers to an interruption in the normal conduction pathway of the heart. The types of AV block are often described by degrees, which include first-degree, second-degree, and third-degree blocks.
In a first-degree or partial block, there is a delay in conduction between the SA and AV nodes, which can be recognized on the ECG as an abnormally long PR interval.
A second-degree or incomplete block occurs when some impulses from the SA node reach the AV node and continue, while others do not. This can be seen on the ECG as some P waves not followed by a QRS complex, while others appear normal.
In a third-degree or complete block, there is no correlation between atrial activity (the P wave) and ventricular activity (the QRS complex). This means that the impulses initiated by the SA node may not reach the AV node, and the P waves are not followed by QRS complexes.