Bundle of His
|Bundle of His|
|Isolated Heart conduction system showing Bundle of His|
|Heart cut away showing Bundle of His
Schematic representation of the atrioventricular bundle of His. The bundle, represented in red, originates near the orifice of the coronary sinus, undergoes slight enlargement to form the AV node. The AV node tapers down into the bundle of His, which passes into the ventricular septum and divides into two bundle branches, the left and right bundles. Sometimes the 'left and right bundles of His' are called Purkyně or Purkinje fibers. The ultimate distribution cannot be completely shown in this diagram.
The bundle of His is a collection of heart muscle cells specialized for electrical conduction that transmits the electrical impulses from the AV node (located between the atria and the ventricles) to the point of the apex of the fascicular branches. The fascicular branches then lead to the Purkinje fibers which provide electrical conduction to the ventricles, causing the cardiac muscle of the ventricles to contract at a paced interval.
The bundle of His is an important part of the electrical conduction system of the heart as it transmits impulses from the atrioventricular node, located at the inferior end of the interatrial septum, to the ventricles of the heart. The intrinsic rate of the Bundle of His is between 40 - 60 bpm. The bundle of His branches into the left and the right bundle branches, which run along the interventricular septum. The left bundle branch further divides into the left anterior and the left posterior fascicles. These bundles and fascicles give rise to thin filaments known as Purkinje fibers. These fibers distribute the impulse to the ventricular muscle. Together, the bundle branches and Purkinje network comprise the ventricular conduction system. It takes about 0.03-0.04s for the impulse to travel from the bundle of His to the ventricular muscle.
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 are collectively referred to as "infra-Hisian blocks." Specifically, 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 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.
His bundle pacing 
Bundle branch blocks are usually treated with the surgical insertion of a pacemaker.
See also 
- synd/3490 at Who Named It?
- W. His, Jr. Die Thätigkeit des embryonalen Herzens und deren Bedeutung für die Lehre von der Herzbewegung beim Erwachsenen. Arbeiten aus der medizinischen Klinik zu Leipzig, Jena, 1893: 14-50.
- Pramod Deshmukh, MD; David A. Casavant, MS; Mary Romanyshyn, CRNP; Kathleen Anderson, BSN (29 February 2000). "Permanent, direct His-bundle pacing: a novel approach to cardiac pacing in patients with normal His-Purkinje activation". Circulation 101 (8): 836–7. doi:10.1161/01.CIR.101.8.869. PMID 10694526. Retrieved 2008-10-08.
- -1469382599 at GPnotebook
- Atlas of anatomy at UMich ht_rt_vent - "Right atrioventricular bundle branch, anterior view"
- atrioventricular+bundle at eMedicine Dictionary
- Scheinman MM, Saxon LA (2000). "Long-term His-bundle pacing and cardiac function". Circulation 101 (8): 836–7. PMID 10694517.
- thoraxlesson4 at The Anatomy Lesson by Wesley Norman (Georgetown University) (thoraxheartinternalner)