Question

Which of the following describes second degree heart block?

A) there is a longer delay between atrial contraction and ventricular contraction
B) not every atrial contraction is followed by a ventricular contraction
C) not every ventricular contraction is preceded by an atrial contraction
D) the ventricles no longer contract
E) the atria no longer contract

Answer 1

Second-degree heart block is characterized by not every atrial contraction being followed by a ventricular contraction, as seen in an ECG where some P waves are not followed by QRS complexes.

Step-by-step explanation:

The correct answer to the question of which statement describes second degree heart block is B) not every atrial contraction is followed by a ventricular contraction. In second-degree heart block, impulses from the sinoatrial (SA) node sometimes fail to be conducted through the atrioventricular (AV) node. This results in some P waves on an electrocardiogram (ECG) not being followed by a QRS complex, indicating that not every atrial contraction leads to ventricular contraction. However, some impulses do get through, so there are normal P waves followed by QRS complexes. This can be seen in Figure 19.25a where half of the P waves are not followed by QRS complexes.