During cardiac imaging, such as an echocardiogram, a patient may be told they have a Chiari Network within their heart. This finding, which appears as an unusual structure in the right side of the heart, can cause concern. While the network’s appearance is striking, its clinical meaning is not always alarming. This article defines this cardiac structure and explains when this harmless anatomical variation requires careful medical attention.
What Exactly Is a Chiari Network?
The Chiari Network is a remnant structure located within the heart’s right atrium, the chamber that receives deoxygenated blood from the body. It presents as a delicate, web-like, or filamentous structure that is highly mobile within the blood flow of the chamber. These strands are typically attached near the opening of the inferior vena cava and the Eustachian valve.
This network is not a disease but a normal variant of cardiac development. It is an embryological remnant resulting from the incomplete resorption of the right valve of the sinus venosus during fetal development. While this structure usually disappears completely before birth, its persistence in adults is found in approximately 2% to 10% of the population.
Its presence is usually an incidental finding, meaning it is discovered during an imaging test performed for an unrelated reason. Because of its thin, mobile nature, the Chiari Network can sometimes be mistaken for other, more concerning right atrial masses, such as tumors or blood clots.
Understanding the Risk: When Is It Dangerous?
For the vast majority of individuals, the Chiari Network is clinically insignificant and causes no symptoms or adverse health effects. It functions as a benign anatomical variation of the right atrium that poses no threat to normal function. However, there are specific, rare scenarios where its presence can contribute to complications.
Association with Patent Foramen Ovale (PFO)
One area of concern involves its frequent association with other structural variations in the heart’s septum. The Chiari Network is found alongside a Patent Foramen Ovale (PFO) in a significant number of cases, sometimes reported to be as high as 84%. A PFO is a small, flap-like opening between the atria that typically closes after birth but remains open in about a quarter of the population.
The Chiari Network may contribute to the persistence of a PFO by directing blood flow from the inferior vena cava toward the interatrial septum. This combined presence creates a mechanism for a paradoxical embolism, where a clot originating in the body’s veins bypasses the lungs and travels through the PFO into the arterial circulation. This can lead to a stroke or a transient ischemic attack.
Thrombus Formation and Procedural Risk
The filamentous structure can also provide a surface for blood clots (thrombi) to form or become trapped. A large, complex network can sometimes create pockets where blood flow slows, promoting stasis and increasing the chance of local clot formation. These entrapped thrombi can potentially dislodge, causing a pulmonary embolism, or if a PFO is present, a paradoxical embolism.
A different risk arises in patients who require certain cardiac procedures. The complex, mobile nature of the network can interfere with the safe passage of medical devices, such as catheters, guidewires, or pacemaker leads, into the right atrium or ventricle. This can lead to procedural difficulties, entanglement of the equipment, or damage to the heart structures.
Detection, Monitoring, and Clinical Approach
The Chiari Network is most often detected non-invasively using echocardiography, which provides detailed moving images of the heart’s structures. Transthoracic echocardiography (TTE) is usually the initial test, but Transesophageal Echocardiography (TEE) is often used to get a clearer, more detailed view of the right atrial structures and to accurately differentiate the network from a thrombus or vegetation. Specialized 3D echocardiography can also be employed to better visualize the network’s intricate geometry.
Once a Chiari Network is identified, the clinical approach centers on risk stratification, determining if the patient has any associated high-risk features. The physician will specifically look for the presence of a coexisting PFO and assess the network’s characteristics, such as its size, thickness, and degree of mobility. A prominent Chiari Network, defined as 10 millimeters or greater, is considered a high-risk anatomical feature, especially when a PFO is also present.
For patients who are asymptomatic and whose network is an isolated finding, the standard management involves simple observation with no specific treatment. No medication or intervention is necessary when the network is deemed benign.
However, if the network is associated with a history of recurrent embolisms, a high-risk PFO, or significant procedural complications, a more active approach may be considered. Treatment may involve long-term anticoagulation medication to prevent clot formation or, in rare cases, surgical resection of the network. Surgical removal is typically reserved for cases where the network is causing obstruction, persistent hypoxemia, or when its removal is necessary to safely complete a different cardiac procedure.