What are the treatment options and management strategies for a patient with a Chiari network, a rare congenital anomaly of the right atrium?

Chiari Network: Clinical Significance and Management

What is a Chiari Network?

A Chiari network is a benign congenital remnant of the right valve of the sinus venosus that appears as a fenestrated, web-like structure in the right atrium and typically requires no treatment in the vast majority of cases 1, 2. This embryonic remnant is found in approximately 2% of the general population and is usually an incidental finding without clinical consequences 1, 2.

When Does It Matter Clinically?

Associated Cardiac Abnormalities

The Chiari network itself is not pathologic, but it frequently coexists with other cardiac findings that may require attention:

• Patent foramen ovale (PFO) is present in 83% of patients with Chiari network versus only 28% of controls, representing a highly significant association 2
• Atrial septal defects occur in approximately 21% of pediatric patients with prominent Chiari networks 3
• Atrial septal aneurysm is found in 24% of patients with Chiari network 2
• The network may direct inferior vena cava blood flow preferentially toward the interatrial septum, potentially maintaining embryonic flow patterns that favor PFO persistence 2

Paradoxical Embolism Risk

The primary clinical concern with Chiari network is its association with paradoxical embolism, particularly in patients with concurrent PFO 2:

• Intense right-to-left shunting occurs in 55% of patients with Chiari network versus only 12% of controls 2
• Among patients with unexplained arterial embolism, Chiari network prevalence is 4.6% compared to 0.5% in patients evaluated for other indications 2
• In patients with both Chiari network and embolic events, 54% experienced recurrent embolic episodes 2
• The network may facilitate paradoxical embolism by maintaining the embryonic flow pattern that directs blood toward the interatrial septum 2

Rare Complications

While uncommon, the following complications have been documented:

• Thrombus formation on the network itself, which may resolve with anticoagulation 4
• Infective endocarditis involving the network, requiring surgical intervention when medical therapy fails 5
• Device entanglement during transcatheter procedures such as atrial septal defect closure 1
• Supraventricular arrhythmias in 21% of pediatric patients with prominent prolapsing networks 3
• Catheter entrapment during cardiac procedures 1

Diagnostic Approach

Imaging Modalities

• Transesophageal echocardiography (TEE) is the gold standard for identifying Chiari network and assessing for associated abnormalities, particularly PFO and atrial septal aneurysm 1, 4, 2
• Contrast echocardiography should be performed to evaluate for right-to-left shunting through a PFO 2
• Transthoracic echocardiography (TTE) can identify prominent networks in children and young adults but has limitations in older patients 3

Key Assessment Points

When a Chiari network is identified, evaluate for:

• Presence and degree of right-to-left shunting through PFO using contrast study 2
• Associated atrial septal defect or aneurysm 3, 2
• Tricuspid valve regurgitation (present in 16% of pediatric cases) 3
• Evidence of thrombus on the network itself 4
• In pediatric patients, measure the extent of prolapse below the tricuspid annulus 3

Management Strategy

Asymptomatic Patients Without Embolic History

No intervention is required for isolated Chiari network in asymptomatic patients 1, 2:

• Routine clinical follow-up is appropriate 6
• In pediatric patients with prominent prolapsing networks, the extent of prolapse typically decreases with growth, and many associated abnormalities resolve spontaneously 3
• Follow-up echocardiography every 3-5 years can monitor for development of associated abnormalities 6

Patients With Embolic Events

For patients with unexplained arterial embolism and Chiari network with PFO, management should focus on the PFO rather than the network itself:

• Anticoagulation with warfarin is appropriate for patients with presumed paradoxical embolism, particularly if thrombus is suspected on the network 4
• The decision regarding PFO closure should follow standard guidelines for cryptogenic stroke with PFO, considering factors such as recurrent events, high-risk PFO features (large shunt, atrial septal aneurysm), and patient age
• The Chiari network itself does not require surgical excision unless it harbors persistent infected vegetations despite appropriate antimicrobial therapy 5

Procedural Considerations

When performing transcatheter procedures in patients with known Chiari network:

• TEE guidance is essential to avoid device entanglement in the network during ASD closure or other right atrial interventions 1
• Careful catheter manipulation is required to prevent entrapment 1
• Pre-procedural imaging should specifically identify and characterize the network 1

Surgical Intervention

Surgery is rarely indicated for Chiari network itself but may be necessary for:

• Refractory endocarditis involving the network despite appropriate antimicrobial therapy for 2+ weeks with persistent fever and septic emboli 5
• Device entanglement that cannot be resolved percutaneously 1
• Concurrent cardiac surgery for other indications where the network can be addressed if it poses technical challenges

Clinical Pitfalls to Avoid

• Do not attribute embolic events solely to the Chiari network—always search for PFO, atrial septal aneurysm, deep venous thrombosis, and other embolic sources 2
• Do not overlook the network during transcatheter procedures—failure to identify it pre-procedurally can lead to device entanglement 1
• Do not assume the network is always benign—in rare cases it can harbor thrombus or become infected 4, 5
• In pediatric patients, do not rush to intervention—many associated abnormalities resolve spontaneously with growth as the extent of prolapse decreases 3

Prognosis

• The natural history is benign in the vast majority of patients 1, 2
• In pediatric patients with prominent prolapsing networks followed for median 3.2 years, prolapse magnitude decreased by median 2 mm, and many associated cardiac abnormalities resolved spontaneously 3
• Only 37% of pediatric patients required any intervention, and outcomes were generally favorable 3
• When embolic events occur in the setting of Chiari network with PFO, recurrence risk is substantial (54%), warranting aggressive secondary prevention 2