The risk factors for congenital and acquired heart block are different.
Congenital Heart Block
If a pregnant woman has an autoimmune disease, such as lupus, her fetus is at risk for heart block.
Autoimmune diseases can cause the body to make proteins called antibodies that can cross the placenta. (The placenta is the organ that attaches the umbilical cord to the mother's womb.) These antibodies may damage the baby's heart and lead to congenital heart block.
Congenital heart defects also can cause heart block. These defects are problems with the heart's structure that are present at birth. Most of the time, doctors don't know what causes congenital heart defects.
Heredity may play a role in certain heart defects. For example, a parent who has a congenital heart defect might be more likely than other people to have a child with the condition.
Acquired Heart Block
Acquired heart block can occur in people of any age. However, most types of the condition are more common in older people. This is because many of the risk factors are more common in older people.
People who have a history of heart disease or heart attacks are at increased risk for heart block. Examples of heart disease that can lead to heart block include heart failure, coronary heart disease, and cardiomyopathy (heart muscle diseases).
Other diseases also may raise the risk of heart block, such as sarcoidosis and the degenerative muscle disorders Lev's disease and Lenegre's disease.
Exposure to toxic substances or taking certain medicines, such as digitalis, also can raise your risk for heart block.
Well-trained athletes and young people are at higher risk for first-degree heart block caused by an overly active vagus nerve. You have one vagus nerve on each side of your body. These nerves run from your brain stem all the way to your abdomen. Activity in the vagus nerve slows the heart rate.