Bilateral carcinoid heart disease secondary to a massive right-to-left shunt through a patent foramen ovale: a case report.

Background: Carcinoid heart disease (CHD) is a rare complication of neuroendocrine tumours (NET). It typically involves the right-sided heart valves due to the effect of vasoactive substances. Bilateral involvement is uncommon and usually requires a significant right-to-left shunt through a patent foramen ovale (PFO). Case summary: A 75-year-old woman with metastatic well-differentiated NET presented with progressive dyspnoea. Transthoracic echocardiography showed multivalvular involvement, including the tricuspid, mitral, and aortic valves, secondary to CHD. During preoperative assessment for valve replacement, the patient developed refractory hypoxaemia. A large right-to-left shunt through a high-risk PFO was confirmed by transoesophageal echocardiography. Percutaneous PFO closure was performed, which resulted in immediate normalization of oxygen saturation. Unfortunately, a few days later, the patient developed aspiration pneumonia and died of cardiorespiratory arrest. Discussion: To our knowledge, this is the first reported case of bilateral CHD due to a massive right-to-left shunt through a PFO, driven by elevated right atrial pressure and a tricuspid regurgitation jet. This case highlights the importance of assessing for a PFO in patients with carcinoid syndrome and left-sided valvular involvement or unexplained hypoxia. Early recognition and PFO closure may represent a key therapeutic step in selected patients.