Origin of the Chiari Network in the Right Atrium
The Chiari network originates from incomplete resorption of the right valve of the sinus venosus during embryonic development. 1, 2, 3
Embryological Development
The Chiari network is a congenital remnant resulting from incomplete involution of the fetal sinus venosus valves during cardiac development. 1 Specifically, it represents persistence of embryonic structures that normally regress as the heart matures in utero. 3
- The structure forms when the right valve of the sinus venosus fails to completely resorb during fetal development, leaving behind a fenestrated, net-like membrane in the right atrium. 2
- This embryonic remnant typically consists of thin, fenestrated threads and strands that attach to two or more regions within the right atrium. 3
Anatomical Characteristics
The Chiari network appears as a fenestrated membrane consisting of threads and strands located in the right atrium, connecting various structures. 2
- The network most commonly involves the inferior vena cava valve and coronary sinus valve, with strands connecting these valves to the crista terminalis, right atrial wall, or interatrial septum. 4
- Histological examination demonstrates that anomalous coronary sinus valves associated with Chiari networks contain cardiac muscle, distinguishing them from other components. 4
Clinical Prevalence
The prevalence of Chiari networks varies depending on the study population:
- Autopsy studies report occurrence in 1.3-4% of cases, though this figure may underestimate true prevalence. 1
- More comprehensive cadaveric studies found Chiari malformations in 13.6% of cadaver hearts and 10.5% of autopsied hearts, suggesting the anomaly is more common than traditionally cited. 4
- The coronary sinus valve is the most frequently fenestrated component in these malformations. 4
Clinical Significance
While generally benign, the Chiari network can occasionally cause complications:
- A redundant Chiari network may favor persistence of patent foramen ovale, formation of atrial septal aneurysm, atrial thrombus formation, or paradoxical embolism. 1
- In neonates, prominent networks can protrude into the right ventricular inflow tract, causing right-to-left shunting and hypoxemia that typically resolves spontaneously within weeks. 3
- Rare complications include arrhythmias, catheter entrapment during interventional procedures, and compromise of cardiovascular function. 1, 2