What is a significant consequence of untreated third-degree AV block?

Untreated third-degree AV block, also known as complete heart block, leads to a significant disruption in the transmission of electrical impulses between the atria and ventricles of the heart. This disconnect can result in bradycardia, where the heart beats slowly, and it may lead to inadequate cardiac output.

One of the most serious consequences of this condition is the risk of myocardial ischemia, which occurs when the heart muscle does not receive enough blood flow to meet its needs. This can happen because the heart's rhythm is compromised, leading to periods where the heart may not pump effectively enough to supply the coronary arteries with sufficient blood, resulting in angina or even potential heart attacks.

In contrast, the other options presented do not accurately reflect the outcomes associated with untreated third-degree AV block. There is no improvement in heart function or exercise capacity, as the reduced heart rate and inefficient pumping would adversely affect both these areas. Moreover, enhanced electrical conduction does not occur; rather, there is a significant impairment in the heart's ability to conduct electrical signals effectively. Overall, the consequences of untreated third-degree AV block create a critical risk that can endanger the patient's life if not addressed promptly.