What is a Chiari Network?
A Chiari network is a fenestrated, web-like membrane consisting of threads and strands located in the right atrium, representing a congenital remnant from incomplete resorption of the right valve of the sinus venosus during embryonic development. 1
Anatomical Characteristics
- The Chiari network is a reticulated network of fibers connected to the Eustachian valve, identified as the embryological remnant of the right valve of the sinus venosus 2
- It was first described in 1897 by anatomist Hans Chiari 1
- This structure is found in 2% to 3% of the general population 1
- The network is typically thin and small, though it can occasionally be prominent and elongated 3
Clinical Significance
In most cases, the Chiari network is generally not of clinical importance and represents an incidental finding without significant pathophysiological consequences. 1, 2
However, rare complications can occur:
- Thrombus formation on the network, which can serve as a nidus for embolic events including stroke 1, 4
- Catheter entrapment during cardiac procedures such as electrophysiological studies or device placement 1, 5
- Embolus entrapment within the network strands 1
- Arrhythmias in some patients 1
- Device complications during atrial septal defect closure procedures, where the network can become entangled with occluder devices 1
Diagnostic Considerations
- Transesophageal echocardiography (TEE) is the preferred imaging modality for identifying and characterizing a Chiari network, particularly when evaluating for atrial septal defect closure or investigating unexplained embolic events 6, 4
- The presence of an extensive Eustachian valve and Chiari network should be documented during pre-procedural TEE assessment for atrial septal defect closure, as these structures may preclude device placement 6
- A prominent Chiari network can mimic right atrial pathology such as thrombus or tumor, requiring careful differentiation 2
Associated Cardiac Abnormalities
When a prolapsing Chiari network is identified, there is a substantial risk of associated congenital heart defects including:
- Atrial septal defects 3
- Patent foramen ovale (which may facilitate paradoxical embolism) 4
- Supraventricular dysrhythmias 3
- Tricuspid valve regurgitation 3
- Atrial septal aneurysm 3
Important Clinical Distinction
This cardiac structure (Chiari network) should not be confused with Chiari malformation, which is a completely separate neurological condition involving herniation of cerebellar tonsils through the foramen magnum. 6, 7 The shared eponym reflects the same anatomist's contributions but refers to entirely different anatomical abnormalities in different organ systems.