Learn The BasicsTransthyretin amyloid cardiomyopathy (ATTR-CM) is a rare and progressive heart disease characterized by misfolded amyloid fibrils in the heart muscle causing it to thicken. ATTR-CM is an underrecognized cause of heart failure.
The diagnosis of ATTR-CM starts with a clinical suspicion. Doctors can then conduct a number of tests to reach a diagnosis. These include an electrocardiogram, imaging tests such as an echocardiogram, cardiac magnetic resonance imaging (MRI) and positron emission tomography (PET) scan, bone scintigraphy, heart biopsy and genetic testing.
Electrocardiogram
An electrocardiogram is a record of the heart’s electrical activity. The electrocardiogram of patients with ATTR-CM has low voltage patterns and poor R wave progression.
However, this pattern is not specific and an electrocardiogram in itself cannot diagnose ATTR-CM.
Imaging tests
Imaging tests, including an echocardiogram, a heart MRI and a PET scan of the heart, can help diagnose ATTR-CM.
An echocardiogram is a type of ultrasound scan that provides a graphic outline of the heart’s movement. In ATTR-CM, the infiltration of transthyretin amyloid (ATTR) deposits in the heart muscle causes enlargement of the ventricles. The enlargement of the wall separating the two upper chambers of the heart, thickened valves and small left ventricle (the chamber of the heart that pumps oxygenated blood to the rest of the body) can indicate ATTR-CM.
However, an echocardiogram cannot differentiate between ATTR-CM and other types of amyloidosis.
A heart MRI and a PET scan of the heart are also noninvasive tests that can create a detailed picture of the heart. The former uses a magnetic field and radiofrequency waves, while the latter uses radioactive tracers to do so.
Bone scintigraphy
Bone scintigraphy is a specialized radiological procedure that can help identify physical and chemical changes in the bones.
This procedure is considered a highly accurate and noninvasive method of detecting ATTR-CM. It can help visualize how much amyloid fibers have built up in the heart.
ATTR-CM scoring system
Researchers from the US and Japan developed and validated a scoring system to identify patients with heart failure who are at high risk of ATTR-CM. It includes three clinical variables (age, male sex and hypertension) and three echocardiographic variables (ejection fraction, posterior wall thickness and relative wall thickness).
Clinicians use the scoring system to identify patients to test with bone scintigraphy for ATTR-CM to ensure they receive the right treatment.
Heart biopsy
A heart biopsy, considered a minimally invasive technique, involves removing a small amount of heart tissue to evaluate under a microscope.
This approach can identify the ATTR deposits in the heart tissue.
Genetic testing
A mutation in the TTR gene can cause ATTR-CM. So, a genetic test looking for these mutations in the TTR gene can help reach a diagnosis of ATTR-CM.
However, some cases of ATTR-CM, called wild-type ATTR-CM, are not genetic and instead result from the buildup of ATTR deposits. Genetic testing cannot identify this type of ATTR-CM, which occurs even though there is no mutation in the TTR gene.
Reviewed by Harshi Dhingra, M.D., on November 11, 2024.