Chiari-Netz

Three-dimensional

echocardiographic assessment of Chiari’s network relationship with the left ventricular false tendon. A Modified apical five-chamber imaging shows the left ventricular false tendon extending between the interventricular septum and the left ventricle lateral wall. B In the four-chamber imaging of the same patient, the Chiari’s network is observed in the right atrium

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Three-dimensional

echocardiographic assessment of Chiari’s network relationship with the left ventricular false tendon. A Apical four-chamber three-dimensional transthoracic echocardiographic view with the appearance of multiple left ventricular false tendons (arrows). B Modified Four-chamber long-axis view depicting two left ventricular false tendons (arrow) from anterolateral mitral papillary muscle to basal segment of the anterior septal wall. Left ventricular false tendons are restricting the movement of the papillary muscle by pulling toward to interventricular septal wall. Fortunately, mitral valve dysfunction did not emerge secondary to these lesions. C, D Modified apical two-chamber view revealed complex branching left ventricular false tendons (arrow) between the base of anterolateral and posteromedial mitral papillary muscles and chordae tendinea

tehj.springeropen.com • CC-by-4.0

Three-dimensional

echocardiographic assessment of Chiari’s network relationship with the left ventricular false tendon. A, C. Modified two-dimensional echocardiographic examination of two patients shows only two left ventricular false tendons (arrows). However, B, D three-dimensional examination of the same images reveals multiple, mesh-shaped, complex left ventricular false tendon structures (arrows)

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An uncommon anatomic variant present in the right atrium, a Chiari network refers to a filamentous, weblike structure that results from incomplete resorption of the embryologic sinus venosus.

Epidemiology

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

Clinical presentation

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

tricuspid regurgitation
infectious endocarditis
embolic transient ischemic attack and/or stroke
- requires presence of patent foramen ovale

Pathology

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.

Radiographic features

Echocardiography

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.

Transthoracic echocardiography

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;

reticulated network of hyperechoic membranous structures located within the right atrium
- typically originates in the most posterior extent of the right atrium (RA), extending a variable distance medially and inferiorly
- may be attached to various other structures within the RA, including the interatrial septum
freely mobile throughout systole and diastole
- absence of diastolic migration into the right ventricle (RV) or the right ventricular outflow tract (RVOT)
most often tethered to the orifice of the inferior vena cava, around which it may appear to rotate

CT

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