The conduction system is a complex network of cells and fibers in the heart through which electrical impulses travel, triggering a heartbeat. The conduction system is comprised of two nodes (special conduction cells) and a series of conduction bundles or fibers (pathways).

Electrical impulses travel through the healthy heart in a predictable pattern. They are generated in the sinoatrial node (sinus node or SA node), located in the top of the upper-right chamber of the heart (right atrium). Because the SA node determines the rhythm and the rate at which these impulses are emitted, it is known as the heart’s natural pacemaker.

From the sinoatrial node, the impulses spread through the atria, causing the upper chambers of the heart to contract. From the atria, the impulses travel through the walls to the atrioventricular node (AV node), which is located between the atria and the lower chambers of the heart (ventricles). At the AV node, the impulses are regulated, slowed down and sorted to make sure that the correct number of impulses reach their destination.

After passing the AV node, the impulses reach the bundle of His (pronounced “hiss”).  Also known as bundle branches or the His-Purkinje (pur-'kin-jee) system, the bundle of His is located in the muscular wall (septum) between the ventricles. It consists of specialized bundles of nerve tissue that branch off to the left and right ventricles, conducting the impulses to both ventricles.

Once the impulses reach the ventricles, they cause the chambers to contract and pump out blood in a routine and consistent manner. Under normal circumstances, the heart muscle, tissue and conduction cells can trigger 140 to 200 electrical impulses a minute. If rhythms are interrupted, delayed or sent down the wrong path, the heartbeat may beat abnormally (arrhythmia). It may beat too fast (tachycardia), too slow (bradycardia) or irregularly. Problems with electrical signals due to disease or abnormalities can occur anywhere along the heart's conduction pathway

There are special tests that can determine the type of arrhythmia as well as its cause. An electrocardiogram (EKG) is a painless test that measures the electrical impulses as they travel from the sinoatrial node to the ventricles. The EKG can track and record different phases of the journey of those electrical impulses, like five landmarks on a road or five points on a line. These five waves are labeled P, Q, R, S and T.

Each of these five waves is associated with a different electrical activity or pathway in the heart’s conduction system. The P wave is associated with electrical activity in the atria, and the other waves reflect electrical activity in the ventricles. The EKG is used to trace the electrical pulses on their journey through the heart and gives an excellent indication of how well the conductive system is functioning, as well as detecting any underlying problems. An EKG is sensitive enough to pick up abnormalities in the heart’s conduction system even before any symptoms appear.3

Treatment for depends on the type of arrhythmia and the problems it can cause a heart patient. Therapy may include medication, placement of a pacemaker, ablation of extra pathways or surgery. If the arrhythmia is not causing any difficulties, the condition may require no treatment.