Chiari network: a protective filter against pulmonary embolism in a case of polycythaemia

Thrombosis of Chiari's network in the setting of non-bacterial thrombotic endocarditis occurring under non-vitamin K antagonist oral anticoagulation: a case report

Background

Non-bacterial thrombotic endocarditis (NBTE) is a rare condition characterized by sterile thrombi on undamaged valves. We herein report a case of NBTE involving the Chiari's network and the mitral valve, related to a metastatic cancer, and occurring under non-vitamin K antagonist oral anticoagulant (NOAC).

Case summary

A 74-year-old patient with metastatic pulmonary cancer was diagnosed with a right atrium mass during pre-treatment cardiovascular check-up. Transoesophageal echocardiography and cardiac magnetic resonance concluded that the mass was a Chiari's network. Two months later, the patient was admitted for a pulmonary embolism and started rivaroxaban. At 1-month follow-up, the patient underwent a new echocardiography, which showed an increased size of the right atrium mass and the presence of two new masses on the mitral valve. She suffered an ischaemic stroke. Infectious work-up was negative. Coagulation factor VIII was 419%. A NBTE with Chiari's network thrombosis and mitral valve involvement was suspected in the setting of a hypercoagulable state related to the active cancer, and intravenous heparin was started, bridged to vitamin K antagonist (VKA) after 3 weeks. All the lesions were fully resolved on follow-up echocardiography at 6 weeks.

Discussion

This case highlights an atypical association of thrombosis on right and left heart chamber with systemic and pulmonary embolism, related to a hypercoagulable state. Chiari's network is an embryonic remnant with no clinical significance and is exceptionally thrombosed. Failure of treatment by NOAC highlights the complexity of cancer-related thrombosis, particularly in NBTE, and the necessity of heparin and VKA in our case.

Benign Structures Mimicking Right Atrial Masses on Prenatal Ultrasound

Advances in imaging have resulted in more frequent reporting of primitive right atrial structures which can sometimes mimic cardiac tumors in prenatal ultrasound. Prominent crista terminalis and Chiari network are examples of these structures. We describe two cases of pregnant women referred to the fetal cardiology clinic for fetal echocardiography for right atrial masses seen on prenatal ultrasound suspicious of tuberous sclerosis. The first case subsequently diagnosed as crista terminalis and the second case as a prominent Chiari network. Postnatal ECHO confirmed the benign nature of these structures. It is important to differentiate tumors from prominent benign structures in the right atrium in fetal ECHO. The location and the similar echogenicity to the adjacent atrial tissue are clues for differentiation of these structures from atrial tumors.

Obstructing Chiari Network Facilitating Blood Flow Across a Patent Foramen Ovale Causing Hypoxia

A 36-year-old man with progressive dyspnea and hypoxia was found to have a large, partially fenestrated Chiari network accelerating blood flow through a patent foramen ovale with preservation of an embryonic right-to-left atrial flow pattern. He underwent successful percutaneous patent foramen ovale closure with resolution of his exertional symptoms. (Level of Difficulty: Beginner.)

A Nonfatal Massive Pulmonary Embolism in a Very Old Patient: The Protective Filter-Effect of the Chiari Network

The Chiari network, a net-like structure within the right atrium, has been described as an embryonic remnant of no clinical significance. Its role in facilitating paradoxical arterial embolic events and as a potential site for thrombus formation has been reported in the literature. This case illustrates the protective filter-effect of the Chiari network in a 92-year-old women who presented with the clinical signs and symptoms of acute cor pulmonale. Transthoracic echocardiography revealed a large, S-shaped, and extremely mobile right atrial thrombus within the Chiari network. Here, the authors describe how the Chiari network may have prevented the occurrence of a fatal pulmonary embolism acting as a protective factor.

A case of a large Chiari network mimicking a right atrial thrombus

The Chiari network is described as a reticulated network of fibers connected to the Eustachian valve identified as the embryological remnant of the right valve of the sinus venosus. It is an incidental finding without any significant pathophysiological consequences. However, the presence of the Chiari network in the right atrium obliges the physician to differentiate from other right atrial pathologies. We present a case of a large Chiari network mimicking a right atrial thrombus with incidental finding in a 76-year-old man undergoing coronary artery bypass surgery.

Accidental Entrapment of Electrical Mapping Catheter by Chiari's Network in Right Atrium during Catheter Ablation Procedure

A 78-year-old male was admitted to our hospital due to frequent palpitation. His electrocardiogram (ECG) presented regular narrow QRS tachycardia with 170 bpm, and catheter ablation was planned. During electroanatomical mapping of the right atrium (RA) with a multiloop mapping catheter, the catheter head was entrapped nearby the ostium of inferior vena cava. Rotation and traction of the catheter failed to detach the catheter head from the RA wall. Exfoliation of connective tissue twined around catheter tip by forceps, which were designed for endomyocardial biopsy, succeeded to retract and remove the catheter. Postprocedural echocardiography and pathologic examination proved the existence of Chiari's network. The handling of complex catheters in the RA has a potential risk of entrapment with Chiari's network.

Chiari network: A case report and brief overview

The Chiari network is mobile, net-like structures occasionally seen in right atrium near the opening of inferior vena cava and coronary sinus. This is usually of no clinical significance and is often diagnosed incidentally. However, sometimes it may cause diagnostic confusion with right atrial pathologies, and may favour thromboembolism by causing flow obstruction. It may be associated with infective endocarditis, arrhythmias, and migraine. Sometimes, it acts as a physical barrier during invasive procedures. The Chiari network has also been described to protect from pulmonary embolism by acting as an inferior vena cava filter due to its sieve-like effect at the cavo-atrial junction. Here, the Chiari network has been described in a case of Ebstein anomaly of tricuspid valve which produced diagnostic confusion during echocardiography. A brief overview has also been presented.