Accessory “Pseudo” Left Atrium Confirmed by Cardiac Magnetic Resonance Imaging

Accessory chamber is an extremely rare congenital abnormality, which is often detected as an incidental finding on echocardiography. We described a case of accessory pseudo Left Atrium (LA) firstly detected by echocardiography and confirmed by Cardiac Magnetic Resonance imaging (CMR). Case presentation- A 4-year-old girl referred to our center with recent fatigue and exertional dyspnea. A large accessory LA was clearly visible on transthoracic echocardiography. CMR demonstrated an isolated wide base round “auricle like” chamber with large pectinate muscles simulating bear’s paw. The accessory LA’s only connection was to the Left Ventricle (LV) through an orifice that functioned as a dysplastic valve at the level of Left Ventricular Outflow Tract (LVOT). This valve had severe regurgitation and stenosis with no papillary connection. Conclusion- This entity differs from cor-triatriatum of the LA because there is a superior-inferior septum between the two left-sided atria with no interatrial communication and no pulmonary venous drainage to the accessory chamber.