Friday, November 2, 2012

Crista Terminalis

Often incidentally noticed in the right atrium on CT, the crista terminalis is an embryonic remnant of the junction between the sinus venosus and the embryonic right atrial appendage and extends across the right atrium from the SVC to the IVC.

In the adult, the crista terminalis acts as an anatomical boundary line between the right atrium and the right atrial appendage, and this ridge serves as the point of attachment for the anterior pectinate muscles of the right atrial appendage.

The crista terminalis can have a wide variety of appearances, from stubby to long and thin (the examples above show two different shapes). The most prominent pectinate muscle arising from the crista terminalis is termed the septum spurium (present in 80%).

"Crista terminalis. Axial (a) and short-axis (b, c) CT scans show how the crista terminalis (CT) (red arrows)
extends from the SVC to the IVC. The origin of the crest at the interatrial groove is confluent with the Bachmann
bundle (BB) (yellow arrows in a). The septum spurium (SS) (blue arrows in c) is the most prominent anterior
pectinate muscle arising from the crista terminalis." (Ref 1)

The sinoatrial node is located in the superior crista terminalis and can play an important role in the development of arrhythmias.

The most important radiological concern for the crista terminalis is to recognize it as a normal structure, as it can occasionally mimic a mass on echocardiography, especially if it is involved in lipomatous hypertrophy of the septum.

1. Saremi F, Krishnan S. "Cardiac Conduction System: Anatomic Landmarks Relevant to Interventional Electrophysiologic Techniques Demonstrated with 64-Detector CT" November 2007 RadioGraphics, 27, 1539-1565.
2.  Broderick LS, Brooks GN, Kuhlman JE. "Anatomic Pitfalls of the Heart and Pericardium" RadioGraphics 2005; 25:441–453.