The septomarginal trabecula (or moderator band) is a muscular band of heart tissue found in the right ventricle. It is well-marked in sheep
and some other animals, and frequently extends from the base of the anterior papillary muscle
to the ventricular septum
From its attachments it was thought to prevent overdistension of the ventricle, and was named the "moderator band".
However, more recent research has indicated that it is more properly considered part of the electrical conduction system of the heart, and in that capacity it is called the "septomarginal trabecula". The TA name is "trabecula septomarginalis".
The moderator band is often used by radiologists to more easily identify the right ventricle in prenatal ultrasound.