Third-Degree (Complete) AV Block

Third-Degree (Complete) AV Block is a serious heart condition where the electrical signals between the upper chambers (atria) and lower chambers (ventricles) of the heart are completely blocked. This means the heart's natural pacemaker in the atria cannot control the heartbeat, causing the ventricles to beat independently and usually more slowly. The condition affects the cardiovascular system and can lead to symptoms like dizziness, fainting, and fatigue due to reduced blood flow to the body. Because the heart beats inefficiently, it can cause low blood pressure and may lead to heart failure if untreated. It is important to recognize this condition as it can be life-threatening without proper management.

Third-Degree (Complete) AV Block is defined as a complete failure of conduction of electrical impulses from the atria to the ventricles, resulting in atrioventricular dissociation. The atria and ventricles beat independently, with the ventricles generating an escape rhythm that is typically slower and less reliable. This block usually occurs due to fibrosis or ischemic damage to the AV node or the His-Purkinje system, often from ischemic heart disease, degenerative conduction system disease, or medication toxicity. The condition causes significant bradycardia, which can lead to hemodynamic instability and symptoms of low cardiac output. It is a critical cause of syncope and requires prompt recognition due to the risk of sudden cardiac death. Diagnosis and management are essential to prevent complications such as heart failure and cardiac arrest.