C18 A FISTULA BETWEEN LVOT AND LEFT ATRIUM: AN UNKNOWN ORIGIN

Abstract History of presentation A 76–year–old woman presented to our EchoLab for worsening exertional dyspnea. Few weeks prior the patient underwent cardiological examination that showed heart failure with preserved ejection fraction (HFpEF) with bilateral pleuric effusion, severe mitralic regurgitation (MR), moderate tricuspid regurgitation (TR) with an estimated systolic pulmonary artery pressure (sPAP) of 50 mmHg and a mildly increased mean gradient on bioprothesic aortic valve (26 mmHg). Past medical history The patient had a medical history significant for arterial hypertension, hyperlipidemia, diabetes mellitus, permanent atrial fibrillation and HCV–related liver disease. She received double surgical aortic valve replacement in 2015 and 2019, the second procedure was complicated by intraoperatory stretching of mitral anterior leaflet and atrioventricular block treated with implantation of bicameral PMK. In the following weeks, the patient was admitted to hospital for exposure of the PMK generator pocket associated to catether cultures positivity for S. Aureus oxacilline–resistant, thus undergoing to device removal and positioning of a new PMK. Investigations The cardio–thoracic auscultation revealed a bilateral basal reduction of vesicular breath sounds, an apical sweet systolic murmur (suggestive of MR) and a systolic small aortic murmur best heard at the second intercostal space. The transthoracic echocardiography showed a blood flow apparently originating from interatrial septum heading towards the free left atrial wall. The Transoesophageal Echocardiography (TEE) with bubble test ruled out any interatrial communication. The 3D TEE acquisitions clarified that the shunt arose from the left ventricular outflow tract (LVOT), thus allowing the diagnosis of fistula between the LVOT and the left atrium. Follow–up and conclusions The patient underwent a procedure of percutaneous closure of the fistula. One month after this intervention, the patient presented to our department for the cardiological follow–up. We noticed that the closure had been successful with no left residual shunts and a reduction of the transprothesic mean aortic gradient (18 mmHg). This case report highlights the importance of the 3D echocardiography in order to settle uncertain diagnostics whereas the 2D echocardiography alone is not sufficient. Nevertheless, the diagnostic challenge that remains open is to understand whether the etiology of the fistula is iatrogenic or post–infectious.