Complications of carcinoid syndrome

People with carcinoid syndrome may develop other complications such as carcinoid heart disease and carcinoid crisis.

Carcinoid heart disease

Carcinoid heart disease is caused by a build up of plaque or scar tissue in the heart valves and the heart muscle. Over time, the valves become thicker and this can affect how the heart works.

Diagram showing carcinoid heart disease

Doctors don’t fully understand why this happens. They think it’s because some neuroendocrine tumours (NETs) make large amounts of hormones and proteins that build up around the heart. The most common substance that NETs make is serotonin.

Carcinoid heart disease happens in around 5 out of every 10 people with carcinoid syndrome. It is more common in people with NETs that started in the small bowel. 


Symptoms are usually vague. Most people don’t have any symptoms until the carcinoid heart disease is severe. Symptoms include:

  • feeling breathless
  • tiredness (fatigue)
  • a build up of fluid in your body causing swelling
  • weight loss


You usually have a heart test called an echocardiogram. Your doctor might ask you to have an echocardiogram regularly to check your heart. If you have any changes to the way your heart works, you see a doctor that specialises in heart problems and you might have treatment.


Some people need to have surgery to the heart valves. Your doctor replaces the affected valves with an artificial valve (prosthesis). 

You might also have treatment with somatostatin analogues to help with the symptoms of carcinoid syndrome. Doctors think this may also help with carcinoid heart disease. 

Before, during and after surgery, you might need to have a somatostatin analogue called octreotide as a continuous drip into a vein to prevent carcinoid crisis.

You may also have an operation to remove as much of the NET as possible. Doctors call this debulking surgery.

Debulking surgery can help to reduce the amount of hormones and substances made by the NET. This can help with the symptoms of carcinoid heart disease. 

Carcinoid crisis

Carcinoid crisis is a serious version of carcinoid syndrome. It happens when NETs make large amounts of hormones and proteins. 

A carcinoid crisis can happen for no reason. In some people, an anaesthetic or treatment such as surgery or chemotherapy can set it off. 

Symptoms of carcinoid crisis include:

  • feeling dizzy and passing out
  • palpitations (an irregular heartbeat)
  • a whistling sound when breathing (wheezing)
  • redness (flushing) of the skin
Carcinoid crisis is a medical emergency. Contact your doctor and go to your local A&E if you think you have this.

You usually have a somatostatin analogue called octreotide as a continuous drip into your vein to prevent carcinoid crisis. If symptoms continue, you may also have treatment with steroids.


It isn’t easy to cope with carcinoid syndrome and its complications. You might have ongoing symptoms such as diarrhoea that are difficult to control. 

There are things you can do to help you cope with carcinoid syndrome. Practical help and support are available for you and your family. 

Last reviewed: 
23 Mar 2021
Next review due: 
23 Mar 2024
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