A complex system driven by neurons and electrical impulses controls the function of the heart. The atrioventricular node, or AV node, is part of this system. Located between the atria and the ventricles in an area called Koch's Triangle, this collection of nerve and muscle cells conducts signals between the upper and lower chambers of the heart. The AV is sometimes referred to as the Aschoff-Tawara node.
Elements of the heart's electrical system, including the atrioventricular node, were discovered in the early 20th century in the course of the work of several physicians. Discovery of the AV node itself is attributed to Sunao Tawara, but his work coordinated with that of a variety of others studying the same anatomical areas during the same time frame. Work that occurred in the early 20th century also built upon research from the latter half of the 19th century.
The atrioventricular node works in conjunction with the sinoatrial (SA) node. The sinoatrial node is located in the right atrium and functions as a pacemaker. When the SA node produces a signal, that signal must pass through the AV node. In order to ensure the optimal function of the heart and proper blood flow, the antrioventricular node slows this signal so that the ventricles, or lower chambers of the heart, are not triggered to contract until the atria, the upper chambers, have fully contracted. The reduction in speed of the signal's movement is usually as little as one-tenth of a second.
The SA node signals the heart to speed up or slow down, and it adjusts its signals according to the body's needs. During exertion, stress or other situations that require oxygen to be delivered more quickly to body cells, the SA node speeds its signals. The atrioventricular node then moderates these signals so that the different chambers of the heart work in a coordinated fashion.
When the function of the atrioventricular node is disrupted, it can lead to problems in the heart, such as arrhythmia. An arrhythmia is any irregularity in the rhythm of the heart, and it sometimes is caused by malfunctions in the electrical systems that control the heartbeat. Different types of arrhythmias include bradycardia, when the heart beats too slowly; tachycardia, when it beats too fast; beats that occur too early, referred to as premature contraction; and fibrillation, which refers to an irregular, uncoordinated heartbeat. Some arrhythmias can be harmless, but they sometimes must be treated with medications or the placement of an artificial pacemaker.