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| Bundle of His | |
|---|---|
 Isolated heart conduction system showing bundle of His | |
 Heart cut-away showing the bundle of His. Schematic representation of the atrioventricular bundle of His. The bundle, represented in red, originates near the orifice of thecoronary sinus, undergoes slight enlargement to form theAV node. The AV node tapers down into the bundle of His, which passes into theventricular septum and divides into two bundle branches, the left and right bundles. Sometimes the 'left and right bundles of His' are called Purkyně orPurkinje fibers. The ultimate distribution cannot be completely shown in this diagram. | |
| Details | |
| Identifiers | |
| Latin | fasciculus atrioventricularis |
| MeSH | D002036 |
| TA98 | A12.1.06.005 |
| TA2 | 3955 |
| FMA | 9484 |
| Anatomical terminology | |
Thebundle of His (BH)[1]: 58 orHis bundle (HB)[1]: 232 (/hɪs/ "hiss"[2]) is a collection ofheart muscle cells specialized forelectrical conduction. As part of theelectrical conduction system of the heart, it transmits theelectrical impulses from theatrioventricular node (located between theatria and theventricles) to the point of the apex of the fascicular branches via thebundle branches. The fascicular branches then lead to thePurkinje fibers, which provide electrical conduction to the ventricles, causing thecardiac muscle of the ventricles tocontract at apaced interval.
The bundle of His is an important part of theelectrical conduction system of the heart, as it transmitsimpulses from the atrioventricular node, located at the anterior-inferior end of theinteratrial septum, to the ventricles of the heart. The bundle of His branches into the left and the rightbundle branches, which run along theinterventricular septum. The left bundle branch further divides into theleft anterior fascicle and theleft posterior fascicle. These bundles and fascicles give rise to thin filaments known asPurkinje 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 theventricular muscle.
Disorders affecting thecardiomyocytes that make up the electrical conduction system of the heart are calledheart 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 asbifascicular blocks, and the condition in which the right bundle branch, the left anterior fascicle, and the left posterior fascicle are blocked is calledtrifascicular 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.
A 2000 study found that direct His bundle pacing is more effective in producing synchronized ventricular contraction—and therefore in improving cardiac function—thanapical pacing.[3]
These specialized muscle fibers in the heart were named after theSwisscardiologistWilhelm His Jr., who discovered them in 1893.[4][5]
