The bundle of His (BH) or His bundle (HB) ( "hiss"
Medical Terminology for Health Professions, Spiral bound Version
'. Cengage Learning; 2016. . pp. 129–.) is a collection of heart muscle cells specialized for

electrical conduction Electrical resistivity (also called volume resistivity or specific electrical resistance) is a fundamental specific property of a material that measures its electrical resistance or how strongly it resists electric current. A low resistivity i ...

. As part of the

electrical conduction system of the heart The cardiac conduction system (CCS, also called the electrical conduction system of the heart) transmits the Cardiac action potential, signals generated by the sinoatrial node – the heart's Cardiac pacemaker, pacemaker, to cause the heart musc ...

, it transmits the electrical impulses from the

atrioventricular node The atrioventricular node (AV node, or Aschoff-Tawara node) electrically connects the heart's atria and ventricles to coordinate beating in the top of the heart; it is part of the electrical conduction system of the heart. The AV node lies at the ...

(located between the atria and the ventricles) to the point of the apex of the fascicular branches via the

bundle branches The bundle branches, or Tawara branches, transmit cardiac action potentials (electrical signals) from the bundle of His to Purkinje fibers in heart ventricles. They are offshoots of the bundle of His and are important to the electrical conduc ...

. The fascicular branches then lead to the

Purkinje fibers The Purkinje fibers, named for Jan Evangelista Purkyně, ( ; ; Purkinje tissue or subendocardial branches) are located in the inner ventricular walls of the heart, just beneath the endocardium in a space called the subendocardium. The Purki ...

, which provide electrical conduction to the ventricles, causing the cardiac muscle of the ventricles to

contract A contract is an agreement that specifies certain legally enforceable rights and obligations pertaining to two or more parties. A contract typically involves consent to transfer of goods, services, money, or promise to transfer any of thos ...

at a paced interval.

Function

The bundle of His is an important part of the

, as it transmits impulses from the atrioventricular node, located at the anterior-inferior end of the interatrial septum, to the ventricles of the heart. The bundle of His branches into the left and the right

, which run along the interventricular septum. The left bundle branch further divides into the left anterior fascicle and the left posterior fascicle. These bundles and fascicles give rise to thin filaments known as

. These fibers distribute the impulse to the ventricular muscle. The ventricular conduction system comprises the bundle branches and the Purkinje networks. It takes about 0.03–0.04 seconds for the impulse to travel from the bundle of His to the ventricular muscle.

Clinical significance

Disorders affecting the cardiomyocytes that make up the electrical conduction system of the heart are called heart blocks. Heart blocks are separated into different categories based on the location of the cellular damage. Damage to any of the conducting cells in or below the bundle of His is collectively referred to as "infra-Hisian blocks". To be specific, blocks that occur in the right or left bundle branches are called " bundle branch blocks", and those that occur in either the left anterior or the left posterior fascicles are called "fascicular blocks", or "hemiblocks". The conditions in which both the right bundle branch and either the left anterior fascicle or the left posterior fascicle are blocked are collectively referred to as bifascicular blocks, and the condition in which the right bundle branch, the left anterior fascicle, and the left posterior fascicle are blocked is called trifascicular block. Infra-hisian blocks limit the heart's ability to coordinate the activities of the atria and ventricles, which usually results in a decrease in its efficiency in pumping blood.

Pacing

A 2000 study found that direct His bundle pacing is more effective in producing synchronized ventricular contraction—and therefore in improving cardiac function—than apical pacing.

Etymology

These specialized muscle fibers in the heart were named after the

Swiss Swiss most commonly refers to: * the adjectival form of Switzerland * Swiss people Swiss may also refer to: Places * Swiss, Missouri * Swiss, North Carolina * Swiss, West Virginia * Swiss, Wisconsin Other uses * Swiss Café, an old café located ...

cardiologist Cardiology () is the study of the heart. Cardiology is a branch of medicine that deals with disorders of the heart and the cardiovascular system. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery di ...

Wilhelm His Jr., who discovered them in 1893.

References

External links

* – "Right atrioventricular bundle branch, anterior view" * ()
Healthy Heart
{{Authority control Cardiac anatomy Cardiac electrophysiology