Prominent Chiari Network as a Cause of Cyanosis in Infants: A Case Report and Implications for Pediatric Cardiology Practice

ABSTRACT

The Chiari network (CN) is an embryological remnant generally regarded as a benign incidental finding. When large and mobile, it may redirect venous blood across atrial communication and provoke cyanosis. We report a 1‐month‐old infant referred with a presumptive diagnosis of Tetralogy of Fallot whose intermittent desaturation was ultimately attributed to a prominent CN that streamed blood across a sizable atrial septal defect (ASD) in the setting of double outlet right ventricle (DORV). Recognition of this mechanism permitted conservative management until elective repair at 6 months (weight 6 kg). This case adds to the limited number of reports documenting CN‐induced positional right‐to‐left shunting in infants with DORV and underscores how meticulous echocardiography can prevent premature surgery in underweighted neonates.

A prominent Chiari network can cause cyanosis in infants by inducing a positional right‐to‐left atrial shunt. Accurate diagnosis enabled conservative management, delaying surgery until optimal conditions. This case emphasizes the importance of echocardiographic evaluation in differentiating cyanosis mechanisms to guide appropriate treatment in congenital heart disease.

1. Introduction

The Chiari network (CN) is an embryological remnant resulting from incomplete regression of the right venous sinus valve during fetal development. The oxygenated blood is directed from the inferior vena cava (IVC) to the left atrium through the foramen ovale (FO). Echocardiographically, it is identified in all infants aged 1 month and in approximately two‐thirds of older children, appearing as a prominence extending into the right atrium from the IVC ostium (Joyce et al. 2022; Steding et al. 1990; Salameh et al. 2017).

Although typically benign, a prominent CN is associated with rare cardiovascular complications. These include supraventricular arrhythmias, interatrial septal defects, thromboembolism, and, notably, cyanosis in neonates or infants coexisting with a patent foramen ovale (PFO) or atrial septal defect (ASD) (Salameh et al. 2017; Qureshi et al. 2014). In such cases, the CN may redirect right atrial blood flow through interatrial communication, resulting in a right‐to‐left shunt and clinically evident cyanosis. This phenomenon can be positional or triggered by increased right atrial pressure, such as during crying or agitation. Management is usually conservative, as the CN tends to regress relative to other cardiac structures during the first months of life. Most cases resolve spontaneously, and surgical intervention is reserved for severe or persistent symptoms, especially when there is significant obstruction of right ventricular inflow or ongoing hypoxemia (Qureshi et al. 2014).

Recent reports emphasize the clinical diversity of CN‐related pathology, ranging from persistent neonatal cyanosis (Aljemmali et al. 2020; Bouabsa et al. 2022; Takahashi et al. 2023) to arrhythmia and paradoxical embolism in older patients (Takahashi et al. 2023; Brunet‐Garcia et al. 2023; Manerikar and Malaisrie 2022). However, the coexistence of a prominent CN with cyanotic congenital complex defects has been only rarely described—(Farruggio and Caruso 2021; McMahon et al. 2000). We present such a case associated with DORV, highlight its novelty, and discuss the importance and implications of detailed echocardiographic assessment of CN for surgical timing in low‐weight infants.

2. Case Report

We present the case of a previously healthy 1‐month‐old male infant weighing 2.3 kg who was admitted to our Pediatric Intensive Care Unit (PICU) with a prior diagnosis of Tetralogy of Fallot (TOF) made at another center. The patient had a baseline oxygen saturation (SpO₂) of 98% but experienced self‐limiting desaturation episodes of 74% during crying fits. These episodes were initially suspected to be hypoxemic spells typical of TOF based on a functional echocardiogram performed by an intensivist, who subsequently referred the case to the pediatric cardiology team for further evaluation. Physical examination revealed mild tachypnea, tachycardia, hepatomegaly (3 cm), and grade III/VI systolic murmur at the pulmonary focus. Chest X‐ray (Figure 1) revealed cardiomegaly with right atrial enlargement, pulmonary artery prominence, and increased pulmonary flow. Electrocardiography showed sinus tachycardia and right atrial and ventricular hypertrophy. Echocardiography confirmed a prominent CN associated with a large ASD in the ostium secundum, double outlet right ventricle (DORV) with subaortic ventricular septal defect (VSD), moderate right branch pulmonary stenosis, and evidence of pulmonary overflow. During crying, we observed a left‐to‐right shunt through the VSD and laminar antegrade pulmonary flow through the pulmonary artery was observed without infundibular spasm (Figure 2); however, there was a positional right‐to‐left shunt across the ASD induced by the CN (Figure 3). This finding clarified that cyanosis was not caused by TOF but rather by the hemodynamic effects of CN. The patient was managed conservatively with medical treatment for heart failure, including furosemide and enalapril, along with enteral nutritional support using a hypercaloric formula. This approach resulted in partial clinical improvement of heart failure symptoms. Over 2 months, progressive regression of the CN was documented along with resolution of desaturation episodes and cessation of the right‐to‐left shunt across the ASD. At 6 months of age, elective surgical correction of DORV and ASD was successfully performed. At 3 years of follow‐up, the patient remained asymptomatic, with no residual defects or sequelae, and had a normal life without medication.

FIGURE 1.

Chest X‐ray showing cardiomegaly with prominent right atrial enlargement, pulmonary artery imprinting, and increased pulmonary vascular markings, consistent with hyperflow. These findings support the presence of congenital heart disease with pulmonary volume overload against Fallot.

FIGURE 2.

Short‐axis view in color Doppler echocardiography performed during the same hypoxemic spell triggered by the crying episode. The images demonstrate laminar antegrade flow through the infundibulum and pulmonary artery, with a left‐to‐right shunt across the large ventricular septal defect (VSD). These findings rule out infundibular stenosis as the cause of cyanosis, supporting the hypothesis of a positional right‐to‐left shunt through the atrial septal defect (ASD) induced by the Chiari network as the primary mechanism of intermittent cyanosis.

FIGURE 3.

Subcostal coronal view in color Doppler echocardiography performed during a cyanotic spell triggered by a crying episode. The image demonstrates a right‐to‐left shunt across a large ostium secundum atrial septal defect (ASD), intensified by the presence of a prominent Chiari network. The Chiari network redirects blood flow from the inferior vena cava (IVC) toward the left atrium, contributing to the intermittent cyanosis observed in the patient.

3. Discussion

Comprehensive echocardiography revealed that the cyanosis was due to a prominent CN causing a positional right‐to‐left shunt through the ASD, rather than infundibular obstruction. This recognition permitted conservative management and postponed the need for surgical intervention until the patient reached an optimal weight, thereby avoiding the risks associated with neonatal cardiac surgery.

This case emphasizes the importance of including persistent CN in the differential diagnosis of neonatal cyanosis and the adaptation of therapeutic strategies to the unique anatomical and physiological characteristics of each patient with complex congenital heart defects, thereby optimizing clinical outcomes. This case underscores the importance of detailed two‐view (subcostal and transatrial) echocardiographic imaging with color Doppler in any infant presenting with unexplained hypoxemia to identify subtle anatomical features such as a prominent CN that can significantly influence clinical management strategies. Additionally, emerging data suggest that integrating color pulsed‐wave tissue Doppler imaging (PWTDI) can refine the differential diagnosis between true right atrial masses and benign pseudomasses, such as a prominent CN, by analyzing motion coherence and peak velocities, thereby avoiding unnecessary intervention (Hiemetzberger et al. 2008; Sonaglioni et al. 2024). In our patient, this distinction was crucial because TOF‐related hypoxemic spells often require urgent surgical intervention, whereas CN‐induced cyanosis can typically be managed conservatively (Manerikar and Malaisrie 2022). Surgical timing and patient weight are well‐established determinants of outcomes in congenital heart disease. Large series have demonstrated a two‐ to threefold increase in mortality and postoperative morbidity for cardiac surgery in infants weighing less than 2.5 kg. Furthermore, survival rates among infants ≤ 3 kg requiring ECMO after surgery can be as low as 33%. Elective repair of TOF and DORV after 55 days of age has been shown to be safe, without increasing the risk of reintervention, and deferring surgery in asymptomatic or mildly symptomatic infants until 3–6 months reduces postoperative intensive care requirements (Alsoufi et al. 2007; Bhat et al. 2012; Curzon et al. 2008; Gelehrter et al. 2011). In our case, accurate delineation of the cyanosis etiology allowed elective repair under optimal conditions with favorable outcomes, an approach supported by current evidence advocating elective repair between 3 and 11 months of age when feasible (Alsoufi et al. 2007; Curzon et al. 2008).

A prominent CN can have significant clinical implications when mobile or prolapsed into adjacent cardiac structures. It has been associated with rare complications, such as platypnea‐orthodeoxia syndrome, thromboembolism, arrhythmias, and interference during catheter‐based procedures (Schneider et al. 1995). In neonates or infants with coexisting ASD or PFO, it can exacerbate right‐to‐left shunting because of its streaming effect on intracardiac blood flow during episodes of elevated right atrial pressure triggered by crying or exertion (Aljemmali et al. 2020; Bouabsa et al. 2022; Takahashi et al. 2023; Zhao et al. 2025). The management of CN‐related complications remains predominantly conservative, as the natural history of this anomaly is overwhelmingly favorable, with spontaneous regression and symptom resolution observed in most pediatric cases managed conservatively (Aljemmali et al. 2020; Takahashi et al. 2023; Brunet‐Garcia et al. 2023). Of note, the largest pediatric series by Joyce et al. (2022) have demonstrated a median prolapse reduction of approximately 2 mm per year as cardiac structures grow, often accompanied by normalization of associated anomalies such as ASDs and tricuspid regurgitation, over a median follow‐up of 3.2 years, with only a small minority ultimately requiring surgery (8%). As the size of the atrium increases relative to the fixed length of the CN, the degree of prolapse and associated hemodynamic impact diminishes, and pulmonary valve z‐scores also tend to normalize, leading to the spontaneous resolution of symptoms and further reducing the likelihood of intervention. Nonetheless, surgery may be necessary in select cases with persistent cyanosis beyond infancy (Qureshi et al. 2014; Bouabsa et al. 2022; Brunet‐Garcia et al. 2023; Zhao et al. 2025; Li et al. 2025; Katranji et al. 2024), mechanical obstruction to tricuspid inflow (Zhao et al. 2025), and rare but serious complications such as paradoxical embolism and recurrent strokes (Manerikar and Malaisrie 2022). Overall, these findings reinforce that conservative management with close follow‐up is the preferred approach for most patients with CN‐related cyanosis, reserving surgery for the rare instances where symptoms persist or complications develop. The gradual resolution of cyanosis in our patient suggests that conservative management is feasible even in complex anatomy like DORV.

The uniqueness of our case lies in the coexistence of a prominent CN with DORV, a complex cyanotic congenital heart defect, and the pivotal role of CN identification in altering surgical management. In the largest pediatric series, Joyce et al. (2022) reported that 37% of patients with CN had no associated cardiac anomalies and 21% had ASDs or right‐sided valve stenosis. The mechanism by which a prominent CN may contribute to ASDs and right‐sided hypoplasia is hypothesized to involve the redirection of fetal venous flow toward the left atrium, which can enlarge the FO and reduce flow through the tricuspid and pulmonary valves, potentially leading to stenosis or atresia (Joyce et al. 2022; Schneider et al. 1995). Of note, our patient's anatomy represents a novel association: a CN dynamically modulating cyanosis in a biventricular conotruncal defect. Critically, previous reports of CN in complex congenital heart disease (e.g., DORV with mitral atresia, tricuspid atresia, or hypoplastic left heart syndrome) describe anatomies with obligatory univentricular physiology, where early palliative surgery is unavoidable regardless of CN presence. In such cases, cyanosis is attributed to the primary cardiac defect, and the CN is merely an incidental finding and has no impact on surgical planning (Farruggio and Caruso 2021; McMahon et al. 2000). Our patient, however, had biventricular physiology, enabling us to attribute cyanosis to CN‐mediated right‐to‐left shunting through the ASD rather than the DORV anatomy itself. This distinction allowed us to postpone surgery until the patient reached an optimal weight (6 kg at 6 months), avoiding the risks of neonatal intervention. In contrast, Joyce et al.'s cohort did not included patients with CN in complex biventricular defects, and the existing literature on CN in cyanotic heart disease focuses almost exclusively on univentricular pathways.

4. Conclusion

The CN should be included in the differential diagnosis of neonatal or infantile cyanosis when coexisting with PFO or ASD. Our case expands the clinical spectrum of CN, demonstrating its potential to dominate the hemodynamic presentation even in patients with complex defects. Early echocardiographic recognition can prevent unnecessary surgical interventions by enabling conservative management based on its natural regression, even in complex cyanotic congenital heart defects, where its identification is critical for delaying surgery until an appropriate age and weight are achieved for safe complete repair.

Ethics Statement

This study was conducted in accordance with institutional guidelines and ethical standards. Written informed consent was obtained from the patient's parents for the publication of this case report and accompanying images.

Consent

Written informed consent for publication of the case details and accompanying images was obtained from the patient's parents. A scanned copy of the signed consent form can be provided to the journal upon request.

Conflicts of Interest

The authors declare no conflicts of interest.

Rodríguez‐Barrios, C. , Gutierrez‐Rosa I., and Rodriguez‐Gonzalez M.. 2025. “Prominent Chiari Network as a Cause of Cyanosis in Infants: A Case Report and Implications for Pediatric Cardiology Practice.” Journal of Clinical Ultrasound 53, no. 9: 2172–2177. 10.1002/jcu.24097.

Data Availability Statement

The data supporting the findings of this study are available from the corresponding author upon reasonable request.