Extrinsic tricuspid valve compression due to an aortic aneurysm causing significant right to left shunt via a patent foramen ovale: a case report

Background Aortic aneurysms are known to cause compression of adjacent structures including the tracheobronchial tree, oesophagus, and recurrent laryngeal nerve. Extremely rarely, they can lead to compression of the tricuspid valve (TV) annulus. We describe a case where aortic aneurysm caused TV annulus compression and persistent right-to-left shunt through a patent foramen ovale (PFO). Case summary A 75-year-old female was admitted with headache and dizziness. On examination, she had persistent arterial desaturation with oxygen levels reduced to 69% at rest whilst breathing ambient air. Complete blood count demonstrated polycythaemia (Hb 174 g/L). Right to left cardiac shunt was suspected after significant lung and haematologic pathology was excluded. Transoesophageal echocardiography demonstrated a trileaflet aortic valve with an ascending aorta aneurysm and a stretched PFO with persistent right to left shunt across it. The ascending aortic aneurysm was observed coursing superior to and compressing the TV annulus. Invasive haemodynamic data demonstrated prominent 'a' waves in the right atrium, low RV (12/1 mmHg), and pulmonary artery pressures (14/6 mmHg), reduced cardiac output and significant right to left shunt with Qp:Qs 0.6. Computed tomography (CT) angiogram demonstrated a 5 cm fusiform ascending aorta aneurysm that coursed anteriorly causing TV annulus compression. Discussion Tricuspid valve inflow obstruction associated with a right to left shunt across PFO can be an extremely rare complication of aortic aneurysm. This may result in persistent arterial hypoxaemia and secondary polycythaemia.