Acute right to left shunt—Combination of tricuspid valve endocarditis, Chiari network, and ostium secundum atrial septal defect

A case report of a triad causing platypnoea–orthodeoxia syndrome

Background

Platypnoea–orthodeoxia syndrome (POS) is a rare condition characterized by hypoxaemia and dyspnoea when changing from a recumbent to an upright position. Diagnosis requires a high clinical suspicion and is often underdiagnosed.

Case summary

We report a case of POS in a 50-year-old woman with dyspnoea and new-onset atrial fibrillation. Oxygen saturation and dyspnoea worsened as she changed from a supine to a sitting position (96 vs. 86%, respectively). Transoesophageal echocardiography demonstrated enlargement of both atria and right ventricle with reduced systolic function and a large Chiari network (CN). Colour Doppler discovered severe tricuspid regurgitation with tenting and tethering of the valve leaflets. Finally, a bubble test revealed the cause of POS to be a patent foramen ovale along with the severe tricuspid regurgitant jet moving into the left atrium and favoured by the CN. Surgical closure of the foramen ovale resulted in the resolution of symptoms.

Discussion

Platypnoea–orthodeoxia syndrome is most commonly caused by a right-to-left shunt through an anatomical defect of the interatrial septum, typically a patent foramen ovale, combined with elevated right atrium pressure. This case illustrates an uncommon cause of POS in the absence of elevated atrium pressure due to the interplay of three key elements: a patent foramen ovale, tricuspid regurgitation, and the CN. Our aim is to alert physicians to the possibility of an intracardiac shunt as the cause of unexplained and/or refractory hypoxaemia related to position changes. Early recognition of this syndrome promotes timely treatment, greatly improving patient outcomes.

Chiari Network Associated with Hypoxemia in a Neonate: Case Report and Review of the Literature

Chiari network is an embryonic remnant of the right sinus venosus. It appears as a thin, fenestrated membrane attached to two or more regions within the right atrium. Usually, a Chiari network has a benign course; however, rare complications associated with a Chiari network have been reported. We present the case of a neonate with hypoxemia and a Chiari network protruding into the right ventricular inflow tract associated with right-to-left shunting across the patent foramen ovale throughout the cardiac cycle. We noted spontaneous improvement after 3 weeks of life.

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.)