Which assessment finding is most likely in a patient with a third-degree AV block?

In a patient with third-degree AV block, the electrical impulses from the atria do not consistently lead to ventricular contraction due to a complete blockage between the atrioventricular (AV) node and the ventricles. This results in dissociation between atrial and ventricular activity, leading to a significant slowing of the heart rate, which is termed bradycardia.

Bradycardia occurs because the ventricles might only beat at a slower intrinsic rate, usually originating from a junctional or ventricular escape rhythm. The absence of coordinated electrical activity means that the heart cannot effectively respond to the needs of the body, hence the heart rate can drop significantly.

While factors such as high blood pressure, tachycardia, and irregular heartbeat can be associated with various cardiac conditions, they are not characteristic of third-degree AV block. In this specific condition, the hallmark finding is indeed bradycardia, reflecting the profound impact the blockage has on the heart's rhythm and overall function.