A heart transplant is a major operation and there's a risk of several complications.

Some complications can occur soon after the procedure, while others may develop months or even years later.

The main risks associated with a heart transplant are described below.

One of the most common complications of a heart transplant is rejection of the donor heart.

This is where the immune system recognises the transplanted heart as foreign and attacks it.

Rejection usually occurs in the days, weeks or months after the transplant, although it can sometimes happen years later.

Immunosuppressant medication can reduce the risk of this happening, but cannot always prevent it completely.

Symptoms of rejection can include:

• chills and aches
• tiredness
• shortness of breath
• puffy, swollen ankles
• noticeable fast or irregular heartbeats (heart palpitations)
• a slightly raised temperature
• tummy (abdominal) pain

Contact your GP or transplant team as soon as possible if you have these symptoms.

Rejection can usually be treated by increasing your dose of immunosuppressant medication.

One of the most serious complications that can occur soon after a heart transplant is that the donated heart fails and does not work properly.

One of the reasons this might happen is primary graft dysfunction.

You'll be closely monitored after your transplant to check for signs of primary graft dysfunction so treatment can be started as soon as possible.

Treatments for primary graft dysfunction may include using:

• medication to support the new heart
• mechanical circulatory support – a machine that helps pump your blood for you and supports the new heart

The immunosuppressant medication you need to take to prevent rejection can have a number of significant side effects.

These can include:

• increased vulnerability to infections
• weight gain
• kidney problems
• high blood pressure
• diabetes
• weakened bones (osteoporosis)
• an increased risk of certain types of cancer, particularly skin cancer

Speak to your transplant team if you experience any troublesome side effects. Do not stop taking your medication without getting medical advice first.

Immunosuppressant medication will weaken your immune system and make you more vulnerable to infection.

While taking the medication, it's a good idea to:

• report any possible symptoms of an infection to a GP or your transplant team immediately – things to look out for include a high temperature (fever), aching muscles, diarrhoea or headaches
• ensure your vaccinations are up-to-date – speak to a GP or transplant team for advice about any additional vaccines you might need, as some are not safe if you have a weak immune system
• avoid close contact with anyone who has an infection – even if it's an infection to which you were previously immune, such as chickenpox

To help prevent infection, you may be given antibiotics, antifungal medicine or antiviral medication to take for at least the first few weeks or months after your transplant.

Narrowing and hardening of the blood vessels connected to the donor heart is a common long-term complication of a heart transplant.

The medical term for this complication is cardiac allograft vasculopathy (CAV). It tends to occur within the first 10 years after the transplant operation.

CAV is potentially serious as it can restrict the supply of blood to the heart, which can sometimes trigger a heart attack or lead to a recurrence of heart failure.

To check for CAV, you may have a coronary angiography, a type of X-ray used to look at the blood vessels of the heart in more detail.

Medication can help keep CAV under control if it does develop, or some people may need to have another heart transplant.

Find out more about the risks of a heart transplant on the NHS Blood and Transplant website