Carcinoid Heart Disease: A Rare Complication of Metastatic Neuroendocrine Tumor

Carcinoid heart disease (CHD), also known as Hedinger syndrome, is a rare but significant cardiac complication associated with metastatic neuroendocrine tumors (NETs). These tumors secret bioactive substances such as serotonin, leading to fibrotic changes primarily affecting the right-sided heart valves. A case study involving a 69-year-old male presented with a four-month history of diarrhea and a new systolic heart murmur. Transthoracic echocardiogram (TTE) results indicated a left ventricular ejection fraction (LVEF) of 60% to 65%, with severe tricuspid regurgitation and pulmonary valve stenosis. Elevated levels of 5-hydroxyindoleacetic acid (5-HIAA) were detected in a 24-hour urine test, and imaging revealed multiple hypoechoic masses in the liver and mesenteric masses adherent to the small intestine. Furthermore, a biopsy confirmed the diagnosis of a NET. Medical therapy like long-acting somatostatin injection and a peptide receptor radionuclide therapy was ineffective in reversing established valvular pathology, and the patient continued to experience clinical decline, suffering from right-sided heart failure. The patient was able to undergo combined tricuspid and pulmonary valve replacement, which resolved his symptoms. This case exemplifies the successful treatment of a rare syndrome leading to right heart failure.