The eustachian valve is often misdiagnosed as an interatrial thrombus.
The eustachian valve (called a Chiari network when fenestrated) is the persistent portions of embryologic valves of sinus venosus, which is important in utero to direct inferior vena cava blood flow across the fossa ovalis.
The filamentous structures can be differentiated from thrombus by their characteristic "insertion" into the atrial wall.
In echo, a leaf-like linear structure is seen at the junction of IVC and RA.
RV inflow view, subxiphoid view, and TEE is diagnostic because such windows can visualize both Eustachian valve and IVC in the same imaging plane.
Occasionally, a prominent Eustachian valve appears to divide RA into two chambers making apparent cor triatriatum dexter.
Such a condition is hemodynamically insignificant in most adults because the septation by Eustachian valve is generally incomplete.
Chiari network
■ Chiari network is a thin, web-like fenestrated membrane that attaches along the ridge connecting the vena cavae and interatrial septum.
It is found in 2-3% of normal heart at autopsy.
In echo, the Chiari network appears as free free-floating curvilinear structure that waves with blood flow in RA.
The Chiari network is thought to be a variant of the Eustachian valve.
A part of the Chiari network arises from the orifice of IVC like
the Eustachian valve, but the Chiari network is much more mobile and thinner.
