Abstract Body (Do not enter title and authors here): A 56-year-old woman presented to her primary care physician with a 1-year history of facial flushing and short-lived paroxysms of chest pain. An electrocardiogram was performed which showed normal sinus rhythm and p-mitrale. Transthoracic echocardiography (TTE) revealed normal left ventricle (LV) size and function, moderate to severe aortic regurgitation, moderate mitral regurgitation (MR), moderate tricuspid regurgitation (TR), and mild pulmonic regurgitation. An agitated saline study suggested an intrapulmonary shunt (positive after >10 beats). Cardiac magnetic resonance imaging (CMR) confirmed these findings but reclassified the TR and MR as severe and the LV as dilated. CMR also incidentally noted numerous complex hepatic masses, largest measuring 6cm. Dedicated liver MRI confirmed this, and biopsy showed strong, diffusely positive staining for neuroendocrine markers, consistent with a well-differentiated neuroendocrine tumor (carcinoid). Positron Emission Tomography/Computed Tomography (PET/CT) revealed high uptake in the pancreatic head, cecum, and right scapula in addition to known liver lesions. Treatment with octreotide was initiated after obtaining a baseline serum serotonin level 1489 ng/mL (normal 50-220 ng/mL). The patient reported mild symptoms and NT Pro BNP was elevated at 265 pg/mL (normal <125 pg/mL). Given LV dilation, severe valve disease, and likely concealed symptoms, cardiac surgery consultation was pursued. Transesophageal echocardiogram with moderate sedation was deferred due to risk of carcinoid crisis. In coordination with oncology, surgery was scheduled after initiating octreotide. Preoperative octreotide infusion was administered, and she underwent four-valve replacement with bioprostheses. Intraoperatively, all four valves had thickened, retracted leaflets; a 7 mm patent foramen ovale (PFO) was also identified and closed. Pathology of valve specimens showed extracellular plaque deposition and bland spindle cells, consistent with carcinoid valve disease. The patient had an uneventful postoperative course. Carcinoid heart disease is a rare, morbid manifestation of neuroendocrine tumors, mediated by elevated serotonin and other vasoactive substances causing fibrotic valve dysfunction. It usually affects right-sided valves, but left-sided involvement may occur with intracardiac shunt or pulmonary metastases. This case illustrates the multidisciplinary diagnosis and management of an exceedingly rare form of carcinoid heart disease.