In third-degree AV block, what is there a lack of between the atria and ventricles?

In third-degree AV block, there is a complete dissociation between the electrical signals of the atria and the ventricles. This means that while the atria may be contracting and generating their own electrical impulses, these signals do not reach the ventricles due to a blockage at the atrioventricular node. As a result, the ventricles are unable to respond to the atrial impulses.

This lack of electrical communication is critical because it leads to an independent rhythm for the atria and ventricles, which can significantly impact cardiac function. The atria may continue to beat at their normal pace, but the ventricles often respond at a much slower rate, determined by an escape rhythm or pacemaker activity located in the ventricles. This dissociation can lead to symptoms of decreased cardiac output, such as fatigue, dizziness, and even syncope.

Regarding the other choices, while blood flow may be influenced by the condition, the primary issue is the absence of electrical signals. Heart rate correlation is affected because the atrial and ventricular rates are no longer synchronized. Mechanical contraction is also impacted since the lack of electrical communication prevents the ventricles from contracting in response to atrial activity, but it originates from the disrupted electrical conduction rather than being the primary