What is a common cause of third-degree AV block?

Third-degree AV block, also known as complete heart block, results when there is a complete failure of the electrical signals to travel from the atria to the ventricles. A common cause of this condition is ischemic heart disease or degeneration of the conduction system. Ischemic heart disease can lead to damage in the heart tissue, particularly within the areas that support conduction pathways, such as the atrioventricular node.

This degeneration can arise from the ischemia (lack of blood flow) that occurs during heart attacks or chronic coronary artery disease. Over time, the electrical conduction system can deteriorate, causing a complete dissociation between atrial and ventricular rhythms, which is characteristic of third-degree AV block. This leads to severe bradycardia and can manifest with significant clinical symptoms, as the heart is unable to coordinate the pump function effectively.

In contrast, some of the other options presented may lead to arrhythmias but are less frequently associated specifically with third-degree AV block. For instance, congenital heart defects and electrolyte imbalances affect cardiac function and rhythm but are not the primary causes of complete heart block. Similarly, while viral infections can cause myocarditis, they are not commonly noted as a direct causative factor in the development of third-degree