1112 Discovering the origin of a mysterious heart cavity

Abstract Left atrial appendage aneurysm is an infrequent cardiac malformation, with less than 150 cases reported in the literature. It is a congenital anomaly in the majority of cases, related to a dysplasia of pectinate muscles and atrial muscle bands, which tends to grow with age. At the present time, and despite of being not considered in current guidelines, surgical resection is the standard of treatment in the current literature, even in asymptomatic cases, based on cardiovascular morbidity and mortality by predisposing to atrial tachyarrhythmia, thromboembolism, and other rare conditions as coronary or left ventricular compression and rupture of the aneurysm. We report the case of a 53-year-old male patient presenting an episode of supraventricular paroxysmal tachycardia with the casual finding of a mysterious cavity in the transthoracic echocardiography. We found out the presence of a 50 mm cavity adjacent to the left atrium and left ventricle, with a bidirectional blood flow between the left atrium and the cavity when applying Doppler color and with contrast echocardiography. Given this finding, several differential diagnosis had to be considered, including vascular and structural disorders. In order to clarify the diagnosis, a cardiac magnetic resonance was performed. It revealed the presence of a huge aneurysm of the left atrial appendage (50 x 53 mm) causing a mild compression of the left ventricle, with no thrombus and no other significant findings. Due to its size, the compression of the left ventricle and the history of atrial arrhythmia we decided to manage it with an invasive approach by performing a middle thoracotomy, in order to prevent potentially serious complications. Abstract 1112 Figure. CMR 3D reconstruction; echocardiography