Moderator band (septomarginal trabecula)
Trabecula septomarginalis
Also known as: septomarginal trabecula, moderator band
The moderator band is a muscular bridge across the right ventricle, running from the interventricular septum to the base of the anterior papillary muscle. It carries part of the right bundle branch.
Overview
The moderator band carries a branch of the right bundle branch across the ventricular cavity. This shortcut lets the anterior papillary muscle contract in time, so the tricuspid chordae are already tight when ventricular pressure peaks. The name comes from an old, now abandoned idea that the band "moderated" over-distension of the right ventricle.
The moderator band is a hallmark of the morphological right ventricle. On echocardiography the right ventricle is recognised by coarse trabeculation, a moderator band and a tricuspid valve whose septal leaflet attaches lower than the mitral valve. This matters in complex congenital heart disease, such as congenitally corrected transposition.
- Location
Lower part of the right ventricle, from the septomarginal trabecula on the septum to the base of the anterior papillary muscle.
Function
- Carries part of the right bundle branch directly to the anterior papillary muscle.
- Coordinates tricuspid valve closure with right ventricular contraction.
- Identifies the morphological right ventricle on echocardiography.
Clinical significance
Ventricular ectopy origin
The moderator band can be the source of ventricular premature beats and of triggers for ventricular fibrillation. These can be treated by catheter ablation.
Echocardiographic pitfall
A prominent moderator band can be mistaken for a right ventricular thrombus or tumour.
Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.