Correctly diagnosing transthyretin amyloid cardiomyopathy (ATTR-CM) can be a challenging process. This rare, progressive disease of the heart muscle is underrecognized by health care professionals and is often overlooked or misdiagnosed, leading to delays in proper diagnosis and treatment.
Differentiating ATTR-CM from other cardiac conditions requires a series of increasingly accurate noninvasive diagnostic tests. If doubt remains, doctors can confirm ATTR-CM with a biopsy that tests for amyloid fibril deposits.
What is ATTR-CM?
Transthyretin amyloidosis cardiomyopathy (ATTR-CM) is a rare progressive disease of the heart muscle that leads to congestive heart failure. It occurs when the transthyretin protein produced by the liver is unstable. Symptoms include fatigue; shortness of breath; irregular heart rate or palpitations; swelling of the legs, ankles and stomach; brain fog; wheezing; and dizziness. It often goes underdiagnosed because of a lack of awareness and knowledge of the disease. There is currently no cure for ATTR-CM.
When are biopsies performed in an ATTR-CM diagnosis?
A comprehensive approach to ATTR-CM diagnosis includes the use of noninvasive diagnostic tools such as echocardiogram, echography, cardiac magnetic resonance imaging, nuclear scintigraphy and genetic tests, and blood and urine tests. In most cases, you doctors will correctly identify ATTR-CM as a result.
Read more about ATTR-CM testing and diagnosis
But if any of the test results are inconclusive or ambiguous, your doctor may order a biopsy to confirm the diagnosis. Bone scintigraphy results may be inconclusive or negative. The presence of gammopathy — abnormal antibodies in the blood — may also require a biopsy.
What kind of biopsy is performed in an ATTR-CM diagnosis?
Your doctor may use cardiac biopsy and extracardiac or noncardiac-related biopsies to confirm an ATTR-CM diagnosis. They include the following.
Endomyocardial biopsy: This is a biopsy of the heart in which a small amount of heart tissue is collected from the inner lining of the heart muscle. It is an invasive procedure that is accurate and relatively safe, with minor complications occurring in fewer than 6% of cases. The sample is then tested for amyloid fibrils. If amyloid fibrils are present, the sample is tested again to determine if they are TTR amyloid fibrils.
Salivary gland biopsy: This extracardiac biopsy requires a local anesthetic before an incision is made in the lower lip. It is easily performed and low-risk for the patient. It is more commonly chosen over a heart biopsy to confirm an ATTR-CM diagnosis because it is quick and painless.
Abdominal fat pad biopsy: This extracardiac biopsy is performed using needle aspiration of fat under the skin. The skin is numbed beforehand, but the procedure creates pressure and discomfort in the abdominal zone being biopsied. It carries minor risks of infection, bruising or bleeding. It is less diagnostically accurate in ATTR-CM and is more often used in AL amyloidosis diagnosis.
Biopsy is no longer a mandatory diagnostic test when identifying ATTR-CM. But when noninvasive tests are inconclusive or ambiguous, a biopsy is used to confirm diagnosis.
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