Final answer:
The three atrial conduction abnormalities are first-degree block, second-degree block, and third-degree block.
Step-by-step explanation:
There are three atrial conduction abnormalities: first-degree block, second-degree block, and third-degree block.
A first-degree block occurs when there is a delay in the conduction of electrical signals between the sinoatrial (SA) node and atrioventricular (AV) node. This is indicated by a prolonged PR interval on an electrocardiogram (ECG).
In a second-degree block, some impulses from the SA node reach the AV node and continue, while others do not. This can be seen on an ECG as some P waves not followed by a QRS complex.
A third-degree block is the complete blockage of electrical conduction from the atria to the ventricles. In this case, there is no correlation between atrial activity (P wave) and ventricular activity (QRS complex) on an ECG.