Carcinoid heart disease occurs when active secretory products of lowgrade neuroendocrine tumors damage the endocardium of the heart. The most common setting involves jejunoileal carcinoids metastatic to the liver, allowing access to the right heart (Table 175.1). Because pulmonary endothelium, like the liver, also inactivates carcinoid secretory products, left-sided cardiac involvement is rare.

Carcinoid heart disease refers to valvular damage related to elevated serum tachykinins, serotonin (5-hydroxytryptophan), and 5-hydroxyindoleacetic acid, a metabolite of serotonin.^2,3,4,5 These circulating agents induce fibroblast proliferation, with possible thrombus formation and increased permeability of vascular endothelium on valve surfaces.⁶ Cardiac involvement is almost always on the right side, with fibrous endocardial plaques formed on the leaflets of the tricuspid and pulmonary valves and subvalvular apparatus. Left-sided involvement implies a cardiac shunt or excess tumor burden that overcomes the capacity of lung endothelial cells to metabolize serotonin. The role of serotonin in the pathogenesis of the valvular disease has been reinforced by the fact that fenfluramine, a serotonin agonist used as appetite suppressant, induces a valvular disease similar to the one in carcinoid heart disease.⁷ Drugs used to treat Parkinson disease, which are dopamine agonists, have been found to have similar effects.⁸

Jejunoileal carcinoids have a 50% to 75% rate of liver metastasis. Among patients with liver metastases, about 20% show symptoms of carcinoid syndrome,⁹ of whom ˜40% develop carcinoid heart disease.⁵ Therefore, overall, carcinoid syndrome occurs in fewer than 10% of patients with jejunoileal carcinoid tumors.

The most frequent symptoms of carcinoid syndrome are cutaneous flushing, gastrointestinal hypermotility, and cardiac involvement.² Carcinoid heart disease is the initial presentation of the tumor in as many as 20% of patients. Most patients diagnosed with carcinoid heart disease have liver metastases. The vast majority of patients with carcinoid heart disease have signs of right heart failure, initially resulting in fatigue, peripheral edema, and dyspnea on exertion. Echocardiography is the principal imaging modality used in the assessment of carcinoid heart disease. Cardiac magnetic resonance imaging enables more accurate quantification of regurgitant volumes and right ventricular ejection fraction. Furthermore, carcinoid plaques can be directly visualized using delayed enhancement imaging with gadolinium.^10,11

Ovarian carcinoid heart disease is rare, as only 0.3% of carcinoid tumors are ovarian in origin. Cardiac involvement may occur at the initial presentation or years after excision of the primary tumor.^12,13