Saturday, November 3, 2012

Eustachian Valve

At the other end from the crista terminalis is the eustachian valve. This structure is also known as "the valve of the IVC" and occurs at the IVC/RA junction. It is theorized to help direct blood flow from the IVC to the foramen ovale in the fetus.

The red transparent oval shows how the intact eustachian valve in the fetus would help direct blood flow through the foramen ovale, bypassing the right-sided circulation

The Eustachian valve occasionally has remnants thick enough to be detected on cardiac CT, ECHO, and sometimes, even with angiography. 

Practically, the Eustachian valve is not as commonly seen as the crista terminalis due to incoming unopacified blood from the IVC. But similiarly to the crista terminalis, probably the most important thing about recognizing the eustachian valve is not confusing it with clot or tumor. If you're trying specifically to image it, then the four-chamber view may be the best orientation.  Some believe it to play a role in fixed conduction block during atrial flutter, and it can be a target for ablation. Eustachian valve endocarditis has also been reported.

In the first image, a prominent eustachian valve is noted and measured.  In the second image, vegetations on a prominent eustachian valve were thought to be the source of the patient's endocarditis. (Ref 4 & 5)

1. Broderick LS, Brooks GN, Kuhlman JE. "Anatomic Pitfalls of the Heart and Pericardium" RadioGraphics 2005; 25:441–453.
2. Saremi F, Pourzand L, Krishnan S, et al. "Right Atrial Cavotricuspid Isthmus: Anatomic Characterization with Multi–Detector Row CT" June 2008 Radiology, 247, 658-668.
3. "Clinical Cardiac CT: Anatomy and Function" Halpern E. 2nd ed.
4. James PR, Dawson D, Hardman SMC. "Images in cardiology: Eustachian valve endocarditis diagnosed by transoesophageal echocardiography" Heart 1999;81:91
5. Chuah SS, Al-Mohammad A. "Large Eustachian valve and kyphoscoliosis" Heart 2005;91:e17