The heart, in particular the heart valves have many serotonin receptors. Some NETs produce excessive serotonin which can affect the heart by causing the heart valves that are normally elastic tissue, to instead thicken and stiffen (fibrosis). Fibrosis affects the way the heart valves on the right side of the heart open and close, and can result in blood flows problems through the heart and lungs. This can cause symptoms such as breathlessness, fatigue, swollen ankles and irregular heartbeat.
It is estimated that between 20-50% of people with carcinoid syndrome have carcinoid heart disease and may eventually develop heart failure.
Whilst carcinoid heart disease cannot be reversed, treatment can prevent further deterioration. This usually consists of treatments to decrease hormone production (SSAs, liver-directed therapy, or even debulking surgery). Patients may be referred to see a cardiologist and there may be medications to help preserve heart function.
Ultimately, some patients with carcinoid heart disease may be advised to have heart surgery to replace the fibrosed valves. As the above treatments are more effective in treating early carcinoid heart disease, and valve damage is irreversible, echocardiography should be considered regularly in NET patients, particularly those with functional NET or known carcinoid heart disease.
