Final answer:
AV blocks refer to interruptions in the normal conduction pathway of the heart. There are three types of AV blocks: first-degree, second-degree, and third-degree.
Step-by-step explanation:
AV blocks refer to interruptions in the normal conduction pathway of the heart. There are three types of AV blocks: first-degree, second-degree, and third-degree. First-degree AV block is characterized by a delay in conduction between the SA and AV nodes, seen as an abnormally long PR interval on an ECG. Second-degree AV block occurs when some impulses from the SA node reach the AV node and continue, while others do not, resulting in P waves not followed by a QRS complex. Third-degree AV block, also known as complete heart block, occurs when there is no correlation between atrial activity (P waves) and ventricular activity (QRS complex).