Transthyretin Amyloid Cardiomyopathy: A Rare Cause of Heart Failure

Transthyretin amyloid cardiomyopathy (ATTR-CM) describes a life-threatening, progressive condition that is classified as either hereditary or wild-type. The hereditary type is caused by a gene mutation, whereas the wild-type form doesn’t have a genetic link. Unfortunately, the condition is often under-diagnosed and unheard of, even within the heart failure community. Despite its rarity, it is important we increase awareness of the condition so people can be diagnosed earlier and achieve better outcomes.

What causes ATTR-CM?

Both types of ATTR-CM are caused by deposits of aggregates of proteins, called amyloid fibrils, into the heart.1 These fibrils deposit into the heart and stiffen the walls, leading to a condition called cardiomyopathy. Cardiomyopathy means that the heart’s ability to pump blood to the rest of the body is impaired because the walls can't relax and squeeze easily. The end stages usually result in congestive heart failure.

Presentation and symptoms

ATTR-CM is debilitating and impacts daily activities of living. People usually present with a wide variety of symptoms, including low blood pressure upon standing, fainting, and atrial fibrillation. However, some may present with no symptoms. In many ways, the presentation is similar to that of traditional heart failure, with swelling of the feet and ankles and shortness of breath. However, with ATTR-CM, there may be additional symptoms, such as numbness or tingling in the hands and/or feet, back pain, and carpal tunnel syndrome.2 These symptoms are referred to as polyneuropathy. Furthermore, the amyloid deposits deposit not only in the heart, but can also form deposits in the kidneys and liver.

What are the risk factors?

Risk factors for hereditary ATTR-CM include:3

  • Family history of ATTR-CM or heart failure
  • Age 50 and over; however, symptoms can present in early adulthood, or late in one’s life
  • Male gender
  • African American ethnicity

Risk factors for wild-type ATTR-CM include:

  • Male gender
  • Age 65 years and older

How is it diagnosed?

It is hard to determine how many people have this condition because it is often under-diagnosed. Tests include checking for the malformed protein that people with ATTR-CM have and checking how well other organs, such as the kidney, are working. The following tests can be performed:4

  • Blood test
  • Urine test
  • Imaging tests, such as an echocardiogram (also known as an Echo)
  • Biopsy, where a small piece of tissue is removed from the heart and examined under a microscope
  • Genetic testing

Treatment

Like heart failure, there is no cure for ATTR-CM; the goal of therapy is to help reduce symptoms and help people live longer. There are limited drugs that address the underlying cause of the condition. Many of the medications used to treat heart failure are used to manage symptoms of  ATTR-CM. However, there are some medications used in heart failure that should not be used in ATTR-CM because it can make the condition worse. If there is severe damage, some people my be recommended a heart transplant.

Untreated people have an average survival of 2-5 years, highlighting how important it is for people to be diagnosed as soon as possible.5

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