Heart block (or “AV block”) is a condition in which electrical impulses have been slowed or blocked in their normal path through the heart’s conduction system. The result is a delayed or complete lack of electrical communication between the upper chambers of the heart (atria) and the lower chambers of the heart (ventricles). 

Heart block may be caused by a variety of factors, including many medical conditions such as past heart attacks, myocarditis or electrolyte imbalances. It can also be caused by certain medications (e.g., beta blockers, calcium-channel blockers or digitalis).

Both the symptoms and treatments for heart block depend on its degree of severity. Mild forms of heart block usually produce no symptoms and may not require treatment. However, more severe forms can lead to serious symptoms such as weakness, dizziness, fainting or even sudden cardiac death. Some people with second-degree heart block and virtually all people with third-degree or complete heart block will require a permanent pacemaker that can better regulate the heart rhythm.

In rare cases, physicians may create complete heart block to treat the abnormal heartbeats of atrial fibrillation. Medications are often tried first, but if they are unsuccessful, a physician can destroy an area of the heart’s conduction system called the atrioventricular (AV) junction, blocking the errant signals. As with natural cases of complete heart block, these patients require a pacemaker to regulate the heart’s rhythm.