Atrioventricular (AV) block is a condition characterized by a disruption or delay in the electrical signals along the AV node, a cluster of cells that connect the electrical activity across the atria and ventricles of the heart. This can result in abnormal heart rhythms, chest pain, shortness of breath, dizziness, and fatigue. AV block can be classified into three degrees, with first-degree being the mildest and third-degree being the most severe.