NET-Induced Carcinoid Heart Disease Affecting Both Tricuspid and Aortic Valves Due to Patent Foramen Ovale and Right/Left Shunt: A Multi-imaging Challenge to Nuclear Medicine.

Carcinoid heart disease (Hedinger syndrome) is a long-term consequence in hormone-active neuroendocrine tumors with hepatic metastases and carcinoid syndrome. Because of serotonin, excess multiple cardiac and pulmonary symptoms evolve, which are further complicated by a patent foramen ovale due to right-left shunting. We present a 53-year-old man with an ileum-neuroendocrine tumor including gross liver metastases and long-term stable disease who subsequently developed Hedinger syndrome. Initially experiencing progressive dyspnea, he eventually experienced severe hypoxemia due to patent foramen ovale. 99mTc-MAA lung perfusion scintigraphy quantitatively identified the right-left shunting, whereas 68Ga-FAPI-46 PET/CT characterized the typical fibrous heart valve thickening due to serotonin-induced fibroblast proliferative properties.