A 16-year-old male presented to the Emergency Department (ED) with right sided chest pain since last night. He reported pain as pressure-like and worse with deep inspiration. The patient also reported one week of sore throat, body aches and mild cough. The patient had no other past medical history other than a spontaneous pneumothorax three months prior in the setting of vaping.
Upon ED arrival, his blood pressure was 113/62, heart rate 92 bpm, respiration rate 19, oxygen saturation 99% and temperature of 98.4F. On physical exam, the patient had a cardiac exam with regular rate and rhythm and bilateral breath sounds without evidence of respiratory distress. Bedside cardiac and lung point-of-care ultrasound (POCUS) was performed, demonstrating a hyperechoic mobile structure in the right atrium with grossly normal ejection fraction (Figure 1). There was no enlargement of the right ventricle or right atrium (RA). Lung sliding was present bilaterally and no pleural effusions were identified on lung POCUS. CT angiogram of the chest showed no evidence of pulmonary embolus or pneumothorax. Cardiology was consulted regarding the POCUS finding which was a Chiari network, an uncommon normal variant and could be followed up as an outpatient.
Chiari network is a weblike structure in the right atrium that result from incomplete resorption of the right valve of embryonic sinus venosus.1 It was first discovered by Dr. Hans Chiari in 1897 on autopsy. It’s described as a fenestrated network of tissue with thread like components attached to wall of right atrium near the entrance of inferior vena cava. Today its prevalence varies from 1-3% and is usually an incidental finding.2
The Chiari network is often considered to be clinically insignificant. However, it can be mistaken for other pathology such as valve vegetations, flail tricuspid leaflet, ruptured chordae tendinae, right heart thrombus or tumor.3,4,7 Transesophageal echocardiogram has been shown to help in differentiating these findings. Despite it being considered as a normal variant, it has been associated with a patent foramen ovale (PFO), thrombus formation, endocarditis, cardiac arrhythmias and catheter entrapment.
A PFO was found in 83% of patients with Chiari network compared to 28% of controls.3 During fetal development, after atrial absorption of the sinus venosus, the atrium divides into two portions separated by the right valve of the sinus venosus. The two portions are the sinus portion with entrance of vena cava, coronary sinus and foramen ovale and the muscular portion with tricuspid valve.1 The incomplete resorption of valve maintains right atrial flow pattern directing blood from the inferior vena cava towards the interarterial septum, which can be associated with a higher incidence of PFO.
