What is a third degree AV block?

As a medical professional with expertise in cardiology, I can explain that a third-degree atrioventricular (AV) block, also known as complete heart block, is a condition where the electrical impulses that control the heartbeat are completely blocked from passing through the AV node, which is the electrical connection between the atria (the upper chambers of the heart) and the ventricles (the lower chambers). In a healthy heart, electrical signals are generated by the sinoatrial (SA) node, which is the heart's natural pacemaker located in the right atrium. These signals then travel through the atria, causing them to contract and pump blood into the ventricles. After passing through the AV node, which slightly delays the signal to allow the atria to finish contracting, the electrical impulse continues down the bundle of His, which is a pathway that runs through the ventricles, causing them to contract and pump blood out of the heart. In a third-degree AV block, the electrical signals from the SA node do not reach the ventricles because the AV node is not conducting the impulses. As a result, the atria and ventricles beat independently of each other. The atria continue to contract based on a slower backup pacemaker, while the ventricles rely on a slower pacemaker in the lower part of the heart. This can significantly reduce the heart's efficiency in pumping blood because the ventricles may not fill with enough blood before they contract. Symptoms of third-degree AV block can range from none to severe, including fatigue, dizziness, shortness of breath, or even fainting. Treatment may include the use of a pacemaker, which is a small device that is surgically implanted to help regulate the heartbeat.

Third-degree atrioventricular block (AV block), also known as complete heart block, is a medical condition in which the nerve impulse generated in the sinoatrial node (SA node) in the atrium of the heart does not propagate to the ventricles.