Carcinoid heart disease – Pathophysiology and mechanism

• Cardiac features of carcinoid syndrome are tricuspid regurgitation, pulmonary stenosis and right ventricular endocardial plaques
• These result in heart failure

Pattern of cardiac involvement in carcinoid syndrome

• Serotonin which is secreted in excess amounts in carcinoid syndrome is the cause of the cardiac manifestations
• It is metabolised in the lungs and liver
• So in most cases of carcinoid syndrome, there is no involvement of the heart
• But in cases of metastatic carcinoid syndrome involving liver and the lungs, the heart is directly exposed to huge quantities of serotonin
• Right heart lesions are seen in liver metastasis and left heart lesions are seen in lung metastasis
  • There is no involvement of the left heart in liver metastasis because serotonin is metabolised in the lungs before reaching the left heart
  • Similarly, the right heart is spared in lung metastasis because the blood passes through the liver before reaching the right heart

Pathology of the cardiac changes in carcinoid syndrome

• High concentration of serotonin causes fibrosis of the papillary muscles and valve leaflets resulting in valve defromity