A 52-year-old man with episodic flushing, secretory diarrhoea, and hepatomegaly undergoes echocardiography. The tricuspid and pulmonary valve leaflets are thickened, retracted, and immobile with free regurgitation; the mitral and aortic valves appear normal. Which mechanism explains the distribution of his valve disease?

• A Immune complex deposition selectively damages right-sided valve endothelium
• B Vasoactive amines reach the right heart directly while pulmonary endothelial monoamine oxidase inactivates them, protecting the left-sided valves ✓
• C Right-sided valves experience higher shear stress, exposing them to platelet-fibrin deposition
• D Metastatic tumour emboli seed the tricuspid and pulmonary valves preferentially

Explanation

In carcinoid heart disease, serotonin and other vasoactive substances secreted by hepatic metastases reach the right heart and induce endocardial fibrous plaque formation with leaflet retraction. The left-sided valves are normally protected because pulmonary endothelial monoamine oxidase degrades these mediators during passage through the lung. Left-sided involvement occurs only when a patent foramen ovale permits shunting or when a bronchial carcinoid secretes mediators distal to the pulmonary circulation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.