What is Second-Degree Heart Block?

Second-degree heart block occurs when the electrical signals, which are usually used in communication between the ventricles and the atria, slow down or are halted. When this occurs, the ventricles do not receive messages that instruct them to pump blood to the rest of the body. Second-degree heart block includes two classifications, type 1 and type 2. Depending on which diagnosis is given, it can be a very serious health concern and can even be fatal.

Ventricles are located in both the brain and the heart. The heart’s ventricles are responsible for pumping blood to the arteries. The atria, also known as atrium, are where blood is held before it is sent to the ventricles. Communication and proper functioning between the ventricles and the atria are crucial to proper blood distribution and flow.

Also known as second-degree atrioventricular block, or second-degree AV block, this type of heart blockage is characterized in two different ways. The first, known as type 1 second-degree heart block, is a progressive type of blockage. It begins with the slowing of signals between the atria and ventricles with each heartbeat until the heart eventually skips a beat. A diagnosis of type 1 second-degree AV block does not always lead to a type 2 blockage. Although this type is not as severe or life-threatening as a type 2 heart blockage, it is still considered to be a serious condition.

Type 2 second-degree heart block occurs when some of the signals are completely missed between the atria and ventricles. In a type 2 second-degree heart blockage, some signals may still transmit as usual, while others are completely missed. Pacemakers, which may work to help regulate signals, are commonly used in an attempt to correct this condition.

Of the two types, type 1 second-degree heart block usually does not progress to a more serious condition. Type 2 heart block, on the other hand, is very serious and often progresses to a syndrome known as Stokes-Adams, which is characterized by sudden fainting. A type 2 second-degree heart blockage also often progresses to a more severe type of blockage classified as a third-degree block.

Second-degree heart block may be caused by certain prescription drugs, including antiarrhythmic drugs and beta-blockers. It may also be caused by other diseases and conditions, such as cardiac tumors, Lyme disease, rheumatoid arthritis and hyperthyroidism. Heart block may also be congenital, and affects both men and women equally.