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, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle ...

specialized for

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

. 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 signals generated by the sinoatrial node – the heart's pacemaker, to cause the heart muscle to contract, and pump blood through ...

, it transmits the electrical impulses from the atrioventricular node (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, are offshoots of the bundle of His in the heart's ventricle. They play an integral role in the electrical conduction system of the heart by transmitting cardiac action potentials from the bundle of His to ...

. The fascicular branches then lead to the Purkinje fibers, which provide electrical conduction to the ventricles, causing the

cardiac muscle Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle ...

of the ventricles to

contract A contract is a legally enforceable agreement between two or more parties that creates, defines, and governs mutual rights and obligations between them. A contract typically involves the transfer of goods, services, money, or a promise to tr ...

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

. The left bundle branch further divides into the

left anterior fascicle The bundle branches, or Tawara branches, are offshoots of the bundle of His in the heart's ventricle. They play an integral role in the electrical conduction system of the heart by transmitting cardiac action potentials from the bundle of His to ...

and the

left posterior fascicle The bundle branches, or Tawara branches, are offshoots of the bundle of His in the heart's ventricle. They play an integral role in the electrical conduction system of the heart by transmitting cardiac action potentials from the bundle of His to ...

. These bundles and fascicles give rise to thin filaments known as Purkinje fibers. 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, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle ...

s 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 block A bundle branch block is a defect in one the bundle branches in the electrical conduction system of the heart. Anatomy and physiology The heart's electrical activity begins in the sinoatrial node (the heart's natural pacemaker), which is situat ...

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 a conduction abnormality in the heart where two of the three main fascicles of the His/Purkinje system are blocked. Most commonly, it refers to a combination of right bundle branch block (RBBB) and either left anterior fa ...

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. 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 may refer to: * the adjectival form of Switzerland *Swiss people Places * Swiss, Missouri *Swiss, North Carolina * Swiss, West Virginia *Swiss, Wisconsin Other uses * Swiss-system tournament, in various games and sports * Swiss Internation ...

cardiologist 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 disease, heart failure, valvular ...

Wilhelm His Jr. Wilhelm His Jr. (29 December 1863 – 10 November 1934) was a Swiss cardiologist and anatomist, son of Wilhelm His Sr. In 1893, His discovered the bundle of His, the collection of specialized cardiac muscle cells in the heart that transmits el ...

, who discovered them in 1893.

References

External links

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