Atrioventricular (AV) block is a condition where the electrical signals between the heart's upper chambers (atria) and lower chambers (ventricles) are delayed or blocked. This disruption can lead to a slower heart rate and may cause symptoms like fatigue, dizziness, or fainting. AV block is classified into three degrees, with the first degree being the mildest and third degree being the most severe. The causes of AV block can include heart disease, certain medications, or damage to the heart from a previous heart attack. Diagnosis typically involves an electrocardiogram (ECG) to monitor the heart's electrical activity. Treatment may vary based on severity and symptoms, ranging from monitoring to the implantation of a pacemaker.