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 Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of ...

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 Atria may refer to: Science *Atrium (heart) (plural: atria), an anatomical structure of the heart *Atria (genus), a flatworm genus in the family Dendrocoelidae * Atria (star) or Alpha Trianguli Australis, a star in the constellation Triangulum Aus ...

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 Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall o ...

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 The interatrial septum is the wall of tissue that separates the right and left atria of the heart. Structure The interatrial septum is a that lies between the left atrium and right atrium of the human heart. The interatrial septum lies at ang ...

, to the ventricles of the heart. The bundle of His branches into the left and the right

, which run along the

interventricular septum The interventricular septum (IVS, or ventricular septum, or during development septum inferius) is the stout wall separating the ventricle (heart), ventricles, the lower chambers of the heart, from one another. The interventricular septum is di ...

. The left bundle branch further divides into the

left anterior fascicle 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 conductio ...

and the

left posterior fascicle 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 conductio ...

. 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

cardiomyocyte Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of ...

s that make up the electrical conduction system of the heart are called

heart block Heart block (HB) is a disorder in the heart's rhythm due to a fault in the natural pacemaker. This is caused by an obstruction – a block – in the electrical conduction system of the heart. Sometimes a disorder can be inherited. Despite the ...

s. 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 block A bundle branch block is a partial or complete interruption in the flow of electrical impulses in either of the bundle branches of the heart's electrical system. Anatomy and physiology The heart's electrical activity begins in the sinoatri ...

s", 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 block Bifascicular block is characterized by right bundle branch block with left anterior fascicular block, or right bundle branch block with left posterior fascicular block on electrocardiography. Complete heart block could be the cause of syncope ...

s, and the condition in which the right bundle branch, the left anterior fascicle, and the left posterior fascicle are blocked is called

trifascicular block Trifascicular block is a problem with the electrical conduction of the heart, specifically the three fascicles of the bundle branches that carry electrical signals from the atrioventricular node to the ventricles. The three fascicles are one in t ...

. 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 Apical means "pertaining to an apex". It may refer to: *Apical ancestor, refers to the last common ancestor of an entire group, such as a species (biology) or a clan (anthropology) *Apical (anatomy), an anatomical term of location for features loc ...

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