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Carcinoid Heart Disease “Hedinger syndrome” is a unique cardiac manifestation of carcinoid syndrome, resulting from serotonin and vasoactive peptide–induced endocardial fibrosis, particularly affecting the right side of the heart.

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![CHD arises because of plaque-like, fibrous deposits on right-sided heart valves (the tricuspid and pulmonic valves) and right-sided chamber endocardium, caused by serotonin-related stimulation of fibroblast growth and fibrogenesis. Carcinoid plaques result in thickening, retraction, and immobility of the tricuspid valve leaflets and subtricuspid apparatus, as well as of the pulmonic valve cusps

Courtesy of Ayoub C, Luis SA, Connolly H; Mayo Clinic Medical Illustrations Unit Illustration demonstrating NET metastases in the liver releasing serotonin, which in turn has caused thickening and retraction of the pulmonic and tricuspid valves as well as endocardial thickening in the RV. How to Best Screen For and Manage Carcinoid Heart Disease - American College of Cardiology. Published 2023. Accessed July 3, 2025. https://www.acc.org/Latest-in-Cardiology/Articles/2023/11/27/12/19/How-to-Best-Screen-For-and-Manage-Carcinoid-Heart-Disease](attachment:d231aeff-ca19-4837-87bb-7d51aa3d6835:Cardio-Onc-EA-Ayoub_Fig1.png)

CHD arises because of plaque-like, fibrous deposits on right-sided heart valves (the tricuspid and pulmonic valves) and right-sided chamber endocardium, caused by serotonin-related stimulation of fibroblast growth and fibrogenesis. Carcinoid plaques result in thickening, retraction, and immobility of the tricuspid valve leaflets and subtricuspid apparatus, as well as of the pulmonic valve cusps

Courtesy of Ayoub C, Luis SA, Connolly H; Mayo Clinic Medical Illustrations Unit Illustration demonstrating NET metastases in the liver releasing serotonin, which in turn has caused thickening and retraction of the pulmonic and tricuspid valves as well as endocardial thickening in the RV. How to Best Screen For and Manage Carcinoid Heart Disease - American College of Cardiology. Published 2023. Accessed July 3, 2025. https://www.acc.org/Latest-in-Cardiology/Articles/2023/11/27/12/19/How-to-Best-Screen-For-and-Manage-Carcinoid-Heart-Disease

Etiopathogenesis

Right-sided predominance is due to inactivation of serotonin in the lungs.

• Cause: Excess serotonin (5-HT), tachykinins, and prostaglandins secreted by neuroendocrine tumors (NETs).
• Mechanism: These hormones stimulate fibroblast proliferation, leading to plaque-like fibrous deposits on endocardial surfaces.
• Key Factor: Usually occurs in patients with liver metastases → serotonin bypasses hepatic metabolism and reaches the heart via systemic circulation.

![Pathophysiology of carcinoid heart disease in patients with neuroendocrine tumours and carcinoid syndrome.

Delhomme C, Arangalage D, Walter T, et al. Carcinoid heart disease associated with digestive neuroendocrine tumours. Hépato-Gastro & Oncologie Digestive. 2021; 28: 1220-1234. Delhomme C, Walter T, Dimitri Arangalage, et al. Carcinoid heart disease in patients with midgut neuroendocrine tumours. Journal of Neuroendocrinology. 2023;35(4). doi:https://doi.org/10.1111/jne.13262](attachment:e49a945e-f726-47f9-bb98-a5b1addb46d2:jne13262-fig-0001-m.jpg)

Pathophysiology of carcinoid heart disease in patients with neuroendocrine tumours and carcinoid syndrome.

Delhomme C, Arangalage D, Walter T, et al. Carcinoid heart disease associated with digestive neuroendocrine tumours. Hépato-Gastro & Oncologie Digestive. 2021; 28: 1220-1234. Delhomme C, Walter T, Dimitri Arangalage, et al. Carcinoid heart disease in patients with midgut neuroendocrine tumours. Journal of Neuroendocrinology. 2023;35(4). doi:https://doi.org/10.1111/jne.13262

Clinical Features

Valvular Involvement:

![Transthoracic echocardiography is the gold standard imaging modality for the assessment of presence, extent, and severity of CHD [62]. Interrogation should include a morphological appraisal of the valves (with an emphasis on the right-sided ones), atrial septum and ventricular septum (patency should be ruled out at baseline), as well as a functional evaluation of all cardiac chambers

AV: aortic valve, AR: aortic regurgitation, AS: aortic stenosis, CMR: cardiac magnetic resonance, LV: left ventricle, MR: mitral regurgitation, MS: mitral stenosis, MV: mitral valve, PR: pulmonic regurgitation, PV: pulmonic valve, RV: right ventricle, RVLS by STE: right ventricular longitudinal strain by speckle tracking echocardiography, TR: tricuspid regurgitation, TV: tricuspid valve

Castillo, J.G., Naib, T., Zacks, J.S. et al. Echocardiography in functional midgut neuroendocrine tumors: When and how often. Rev Endocr Metab Disord 18, 411–421 (2017). https://doi.org/10.1007/s11154-017-9434-z](attachment:d4e2e7f6-23ad-49e8-b9de-347d6612c907:11154_2017_9434_Fig3_HTML.webp)

Transthoracic echocardiography is the gold standard imaging modality for the assessment of presence, extent, and severity of CHD [62]. Interrogation should include a morphological appraisal of the valves (with an emphasis on the right-sided ones), atrial septum and ventricular septum (patency should be ruled out at baseline), as well as a functional evaluation of all cardiac chambers

AV: aortic valve, AR: aortic regurgitation, AS: aortic stenosis, CMR: cardiac magnetic resonance, LV: left ventricle, MR: mitral regurgitation, MS: mitral stenosis, MV: mitral valve, PR: pulmonic regurgitation, PV: pulmonic valve, RV: right ventricle, RVLS by STE: right ventricular longitudinal strain by speckle tracking echocardiography, TR: tricuspid regurgitation, TV: tricuspid valve

Castillo, J.G., Naib, T., Zacks, J.S. et al. Echocardiography in functional midgut neuroendocrine tumors: When and how often. Rev Endocr Metab Disord 18, 411–421 (2017). https://doi.org/10.1007/s11154-017-9434-z

Diagnosis

Biomarkers:

Radiology