Chiari network

Last revised by Yaïr Glick on 11 May 2022

A Chiari network refers to a filamentous, weblike structure in the right atrium that results from incomplete resorption of the embryonic sinus venosus. It is an uncommon anatomical variant.

Prevalence estimates for the general population vary widely, ranging from 2%-10% of randomly selected, asymptomatic patients 2.

While thought to be of no innate clinical significance, the presence of a Chiari network is associated with the following 3:

Resorption of the right valve of the embryologic sinus venosus occurs during the normal development of the right atrium, forming the Eustachian valve and the crista terminalis. Incomplete resorption, however, may result in either the persistence of a prominent Eustachian valve or a Chiari network, which shares the same point of anatomical attachment but differs in appearance. 

A Chiari network may be visualized with both transthoracic (TTE) or transesophageal (TEE) approaches, most often an incidental finding when the former is utilized to investigate an unrelated pathology.

Multiple transthoracic windows and views should be used to adequately assess the right atrium, including the apical 4-chamber view, parasternal right ventricular inflow tract view, and a basally angulated parasternal short axis view. The following grey scale features are characteristic of a Chiari network;

Chiari network can sometimes be seen as a lacelike filling defect but can be challenging to diagnose with confidence due to heterogeneity of contrast enhancement within the right atrium. Identification of its attachment to the inferior vena cava ostium can aid in establishing a diagnosis.

Originally described in 1897 by the Austrian pathologist Dr. Hans Chiari (1851-1916) 4.

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