Bundle of His
Fasciculus atrioventricularis
Also known as: atrioventricular bundle, AV bundle, His bundle, common bundle
The bundle of His is a bundle of conducting fibres that continues from the AV node, passes through the central fibrous body and runs along the membranous septum before dividing into the right and left bundle branches. It is the only normal electrical bridge across the fibrous skeleton.
Overview
The penetrating portion of the bundle passes through the right fibrous trigone (central fibrous body). The branching portion then runs along the lower border of the membranous septum, on the crest of the muscular septum. There it splits into the right bundle branch and the broad left bundle branch.
Like the rest of the His–Purkinje system, the bundle conducts quickly using fast Na⁺-dependent action potentials. Its escape rhythm, if the node above it fails, is about 40/min.
Because it lies just below the right and non-coronary cusps of the aortic valve and next to the tricuspid annulus, it is easily damaged during valve surgery, TAVI, VSD repair or by an aortic root abscess.
- Location
From the AV node through the central fibrous body to the top of the muscular interventricular septum, beneath the membranous septum.
Anatomy
- Arterial supply
Dual supply from the AV nodal artery and the septal perforators of the LAD.
Function
- Carries the impulse from the AV node across the fibrous skeleton to the ventricles.
- Divides into the bundle branches that activate the two ventricles.
Clinical significance
Infranodal (His–Purkinje) block
Block at or below the bundle of His typically causes Mobitz II or complete heart block with a slow, wide-QRS escape rhythm. Causes include age-related fibrosis (Lenègre–Lev disease), anterior MI, valve surgery and TAVI. A pacemaker is usually needed.
Conduction-system pacing
In His-bundle pacing and left bundle branch area pacing, the lead is placed in the conduction system itself. The ventricles are then activated through their normal pathways, which preserves synchronous contraction.
Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.