A 45-year-old woman with metastatic neuroendocrine tumour and flushing develops oedema and ascites. Echocardiography shows tricuspid regurgitation with thickened, shortened tricuspid and pulmonary valve leaflets fixed in a semi-open position. The responsible mediator reaches these valves through:

• A Bronchopulmonary venous drainage into the left atrium
• B Systemic arterial circulation via the aorta
• C Venous drainage directly into the right side of the heart ✓
• D Retrograde flow through the thebesian veins

Explanation

Carcinoid heart disease affects almost exclusively the right-sided valves because serotonin and other vasoactive products released by hepatic metastases drain through the portal vein into the systemic venous return, reaching the tricuspid and pulmonary valves before being detoxified in the lungs. Left-sided involvement occurs only if there is a patent foramen ovale or a bronchial carcinoid whose products bypass pulmonary metabolism.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.