Why heart transplant rejection happens

Your immune system’s job is to find and destroy things in the body that may cause harm. This includes bacteria and viruses. The immune system works to help keep you healthy. But in some cases, the immune system response can lead to problems.

During a heart transplant, a surgeon removes your heart and replaces it with a healthy heart from a donor. Your immune system sees the new heart as a threat and can start to attack it. After a heart transplant, you will need to take medicine for the rest of your life to prevent this from happening. But transplant rejection may still occur. It’s common even in people who take all of their medicine as prescribed.

Types of heart transplant rejection

The types of heart transplant rejection include:

• Acute cellular rejection. This is the most common type. It happens when immune system cells called T-cells attack the cells of your new heart. It happens most often in the first 3 to 6 months after a transplant.

• Humoral rejection. This is a less common type. It’s also known as acute antibody rejection. It can develop during the first month after transplant surgery. Or it can happen months or years after a transplant. With humoral rejection, antibodies injure the blood vessels in your body. This includes the coronary arteries. This can cause problems with the blood flow to the heart.

• Coronary artery vasculopathy. This is a form of ongoing (chronic) rejection. It affects the coronary arteries. These send oxygen and nutrients to the heart muscle. With coronary artery vasculopathy, the inner lining of the blood vessel thickens. This can lead to less blood going to the heart muscle.

What causes heart transplant rejection?

Heart transplant rejection is caused by a normal immune system. Not taking antirejection medicines as prescribed can cause transplant rejection. But many people who take their medicines still have rejection. No one knows for sure why this happens.

Factors that can increase the risk for acute rejection include:

• Genetic mismatch between the heart donor and heart recipient

• Having a recent transplant surgery (rejection risk is highest in the weeks after transplant and then begins to decrease)

• Getting a heart from a female donor

• Being a female recipient

• Being a younger recipient

• Being an African-American recipient

Factors that can increase the risk for chronic rejection include:

• Genetic mismatch between the heart donor and heart recipient

• High cholesterol levels

• Cytomegalovirus (CMV) infection

• Getting a heart from an older donor

• Getting a heart from a male donor

• Being a younger recipient

• History of acute heart rejection

• Coronary heart disease in the donor or the recipient

• Insulin resistance

Symptoms of heart transplant rejection

Rejection may not cause symptoms. The problem may only be found during follow-up tests after the surgery. It’s important to keep all your follow-up appointments.

When symptoms of acute heart transplant rejection occur, they can include:

• Feeling tired or weak

• Fever or chills

• Shortness of breath

• Fast or irregular heartbeat

• Drop in blood pressure

• Swelling of your feet, hands, or ankles

• Sudden weight gain

• Flu-like aches and pains

• Reduced amounts of urine

• Dizziness or fainting

• Nausea or loss of appetite

Chronic heart transplant rejection often has no symptoms. The first symptom may be a heart attack.

Diagnosing heart transplant rejection

Your healthcare provider will ask about your health history and your symptoms. You’ll have a physical exam. You’ll also have tests such as:

• Heart biopsy. A biopsy is a small piece of tissue taken from the right side of the heart to be tested. You may have multiple routine biopsies after a heart transplant. This helps check for rejection. These biopsies often show signs of rejection before any symptoms occur. Finding a rejection early increases the chances it can be treated. Acute rejection is often found with a heart biopsy.

• Blood tests. Acute rejection can be found with a blood test. This test checks for genes linked to transplant rejection.

• Heart function tests. Your healthcare provider may use other standard tests to check your heart function. You may have an electrocardiogram (ECG) to check your heart rhythm. You may also have an echocardiogram to look at your heart movements.

• Blood vessel tests. Other tests may be needed to check for chronic rejection. These tests help give a better look at the blood vessels. You may have a coronary angiography, intravascular ultrasound, or cardiac stress testing. Your healthcare provider can tell you more about these tests.