Final answer:
An AV nodal block refers to an interruption in the normal conduction pathway within the AV node of the heart. It can be categorized into different degrees based on the severity of conduction delay. First-degree blocks show a delay in conduction between the SA and AV nodes, second-degree blocks exhibit intermittent conduction, and third-degree blocks result in independent atrial and ventricular contractions.
Step-by-step explanation:
An AV nodal block refers to an interruption in the normal conduction pathway within the AV node of the heart. The AV node is a clump of specialized myocardial conductive cells located in the inferior portion of the right atrium. It plays a critical role in delaying the transmission of electrical impulses from the atria to the ventricles, allowing for efficient heart function.
AV blocks can be categorized into different degrees based on the severity of conduction delay. First-degree blocks show a delay in conduction between the SA and AV nodes, while second-degree blocks exhibit intermittent conduction where some impulses reach the AV node while others do not. Third-degree blocks show no correlation between atrial and ventricular activity.
On an ECG, first-degree blocks can be recognized by an abnormally long PR interval, while second-degree blocks show P waves without a corresponding QRS complex. Third-degree blocks result in independent atrial and ventricular contractions.