Heart block

Heart block takes place when the SA node sends its electrical signal properly, but the signal is not sent through the atrioventricular (AV) node or lower electrical pathways as quickly as it should be. The condition is most often caused by aging or by the swelling or scarring of the heart that sometimes results from coronary artery disease. There are several types of heart block, and they are named by their degree of severity.

First-degree heart block means that impulses are moving through the AV node too slowly.

Second-degree heart block means that impulses are traveling through the heart’s atria but are delayed in the AV node. Because of this delay, the ventricles do not beat at the right moment.

Third-degree heart block means that no impulses are reaching the ventricles. To make up for this, the ventricles use their own “backup” pacemaker with its slower rate. Because a gap in time is likely to occur between the impulse from the atria and the impulse from the backup unit, a person may faint. This is known as a Stokes-Adams attack. Third-degree heart block is very serious and can lead to heart failure or death.