Transthyretin amyloid cardiomyopathy (ATTR-CM) is a rare type of heart disease that can cause a thickening of the heart muscle. It may lead to heart failure.

ATTR-CM is typically underdiagnosed. The condition can occur when certain proteins in the blood do not form correctly and start to build up in the heart. This can cause symptoms such as shortness of breath and swelling in the legs and feet.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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Transthyretin amyloid cardiomyopathy (ATTR-CM) is a rare type of heart muscle disease that can lead to heart failure.

Transthyretin is a type of protein that the liver produces. The proteins circulate through the bloodstream to the rest of the body. When transthyretin proteins do not form correctly, they can convert into amyloid that deposits in the tissue of the heart muscle, known as the myocardium.

The buildup of misshapen proteins in the heart can lead to cardiomyopathy, a term that describes problems with the heart muscle.

The heart muscle can become thicker, stiffer, or larger than normal, which can prevent the heart from effectively pumping blood around the body.

There are two types of ATTR-CM. The most common type is wild-type ATTR-CM (wATTR-CM), which typically develops as a person ages.

Hereditary ATTR-CM (hATTR-CM) can run in families. This type can occur when a person inherits a certain alteration of the transthyretin gene that can prevent transthyretin proteins from forming correctly.

In both types of ATTR-CM, the transthyretin proteins do not form in the typical way, which can cause them to build up in the heart.

There is no evidence to suggest a direct cause of ATTR-CM other than it being a potential part of the aging process or a person inheriting a gene mutation.

A 2023 article suggests that 83% of people with ATTR-CM are male.

Females may be more likely to develop hATTR-CM than wATTR-CM. According to a 2020 study, 29% of people with hATTR-CM are female, whereas only 9% of people with wATTR-CM are female.

A 2019 study suggests that a person is most likely to develop wATTR-CM if they are over the age of 60 years. However, hATTR-CM may occur between the ages of 30 and 80 years, depending on the type of gene alteration a person inherits.

ATTR-CM may be more common in males with heart conditions such as left ventricular hypertrophy and heart failure with preserved ejection fraction. These conditions can cause a thickening of the wall in the left ventricle, the heart’s main chamber.

In the United States, a person may be more at risk of inheriting a gene variation that can lead to hATTR-CM if they are African American.

ATTR-CM can be difficult to diagnose as it may present with similar symptoms to other heart conditions or no symptoms at all.

The most common symptom of ATTR-CM is shortness of breath, particularly when a person is at rest.

Other symptoms can include:

A person with wATTR-CM may develop carpal tunnel syndrome, a condition that causes pressure on a nerve in the wrist. Symptoms can include pain, numbness, and tingling in the fingers and hands. People with wATTR-CM may also be more likely to develop an irregular heartbeat or a change in heart rhythm.

A person with hATTR-CM may experience pain, tingling, and numbness in the hands and feet.

Because ATTR-CM typically presents with similar symptoms to other heart conditions, diagnosis can be challenging.

The first line of testing a doctor may use when a person presents symptoms of ATTR-CM may be an electrocardiogram (ECG). However, a 2020 review refers to an older study suggesting that an ECG may only detect ATTR-CM in up to 40% of people with the condition.

Therefore, a doctor will typically recommend a combination of additional tests following an ECG. Some of these may include:

The Food and Drug Association (FDA) has approved one type of medication to treat ATTR-CM. This medication, tafamidis, works by preventing further buildup of transthyretin proteins in the heart.

Tafamidis can slow down the progression of ATTR-CM. However, it cannot reverse it. Also, tafamidis may only be effective if a person starts taking it early on in the development of ATTR-CM.

A person with ATTR-CM may consider a liver transplant. This can remove the gene alteration that produces transthyretin protein. However, this is only possible with hATTR-CM.

Other treatment options involve trying to manage symptoms of ATTR-CM to improve quality of life, such as:

Several other treatments for ATTR-CM are currently undergoing FDA clinical trials.

Research suggests that the average survival rate for a person with hATTR-CM may be 2.5 years.

A person with wATTR-CM may have an average survival rate of 3.5 years. However, this may depend on the stage of the condition. If a person receives a diagnosis in the early stages, the survival rate can be approximately 66 months (5.5 years).

A note on survival rates

A survival rate refers to the number of people who are still alive for a specific length of time after a particular diagnosis.

For example, a 5-year survival rate of 50% of people means that half of the people are still alive at least 5 years after diagnosis.

It is important to remember that these figures are estimates based on previous medical studies. Talk with your doctor about the outlook for your specific condition.

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Transthyretin amyloid cardiomyopathy (ATTR-CM) is a rare type of heart disease with two forms. Wild-type ATTR-CM (wATTR-CM) typically develops when a person is over the age of 60 years and is more common in males. Hereditary ATTR-CM (hATTR-CM) can occur when a person inherits a certain gene variation.

The most common symptom of ATTR-CM is shortness of breath. Other symptoms can include swelling of the legs and feet, coughing, and wheezing.

A doctor may focus treatment on managing symptoms of ATTR-CM. The FDA has approved one medication that can help slow the condition’s progression but cannot reverse its effects.

Survival rates for ATTR-CM may vary depending on the type a person has. The average survival rate may be between 20 months and 3.5 years.