A 64-year-old man was admitted for stroke. Transoesophageal echocardiography showed a membrane extending from the top to the bottom of the right atrium ( Fig. 1 ; Video 1 ). As colour Doppler imaging demonstrated a perforation in the membrane ( Fig. 2 ; Video 2 ), we suspected a CTD but had to rule out the Chiari network. A bubble study was performed. The anterior chamber was opacified while the posterior chamber was not ( Fig. 3 ). The peak velocity of the flow across the membrane was 0.66 m/s and the peak pressure gradient was 1.73 mmHg ( Fig. 4 ). These findings led to a fortuitous diagnosis of CTD with no atrial septal defect. Cor triatriatum is a rare congenital malformation, characterized by the presence of a membrane dividing one of the atria into two chambers. When the membrane is in the left atrium (cor triatriatum sinistrum), it mimics mitral stenosis. When it is located in the right atrium (CTD), it may be asymptomatic. In all cases, the severity of symptoms depends on the existence and size of the communication between the two chambers. The membrane dividing the right atrium has to be differentiated from the Chiari network, which is a fenestrated and filamentous structure with an undulating movement. Three-dimensional echocardiography of the right atrium may be a useful tool. However, when not available, our case study suggests that transoesophageal echocardiography with a bubble study can help to differentiate CTD from the Chiari network, one chamber only being opacified.
