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Transthyretin amyloid cardiomyopathy (ATTR-CM) is a type of heart disease that happens when an abnormal protein called amyloid builds up in the heart. Because the symptoms can look similar to those of other heart conditions, such as heart failure caused by high blood pressure, ATTR-CM is often missed or misdiagnosed.
Understanding the signs of ATTR-CM is crucial for early detection. In this article, we’ll review some of the signs and symptoms of ATTR-CM.
Amyloidosis happens when certain proteins change shape in an abnormal way and clump together, forming amyloid fibrils. ATTR-CM is a type of cardiac amyloidosis that involves the misfolding of a protein called transthyretin (TTR).
TTR misfolding can be caused by a genetic mutation (change) in the TTR gene that’s passed down from parent to child, which is known as hereditary ATTR-CM (hATTR-CM). People with hATTR-CM usually don’t have symptoms until after age 50.
Wild-type ATTR-CM (wATTR-CM) occurs when the normal, nonmutated TTR protein misfolds, typically associated with aging. People with wATTR-CM may have only mild symptoms or none at all in the early stages. If symptoms do occur, they usually show up after age 65.
Normally, TTR is made in the liver and helps carry vitamin A and thyroid hormone through the bloodstream. But when TTR proteins misfold, they can build up in the heart muscle and nerves. This makes the heart muscle stiffer and less flexible, so it’s not able to pump blood effectively. When misfolded TTR proteins get deposited in nerves or other tissues, additional symptoms can occur.
Keep reading to learn about the signs and symptoms that can develop in people with ATTR-CM.
Heart failure happens when the heart becomes too stiff or weak to pump enough blood to meet the body’s needs. Heart failure results from conditions such as hypertension (high blood pressure) or coronary artery disease (narrowing of the blood vessels in the heart).
In people with ATTR-CM, amyloid fibrils build up in the heart walls or valves, making the heart muscle stiff. Because the symptoms resemble those of more common heart conditions, ATTR-CM can be easily overlooked or misdiagnosed.
People with heart failure may experience shortness of breath even with light activity or while resting. This symptom is usually linked to left-sided heart failure, which affects the left ventricle (the heart’s main pumping chamber). When this part of the heart can’t fill or pump properly, blood backs up into the lungs, making it harder to breathe.
ATTR-CM is linked to heart failure with preserved ejection fraction, a type of left-sided heart failure in which the left ventricle has trouble relaxing and filling with blood between beats. People with ATTR-CM generally first experience shortness of breath, followed by coughing or wheezing, especially when lying down.
Edema (swelling from fluid buildup) is usually associated with right-sided heart failure, which can also be caused by ATTR-CM. In right-sided heart failure, the right ventricle (the heart’s lower pumping chamber) is too weak to pump blood to the lungs. Blood can back up in other parts of the body, causing symptoms such as swelling in the liver, abdomen (belly), or legs, feet, and ankles. The fluid buildup can also lead to sudden weight changes.
Other symptoms related to heart failure that can occur in people with ATTR-CM include:
To compensate for reduced pumping efficiency, the heart may beat faster or irregularly. People with ATTR-CM may notice changes in their heart rate and rhythm. It’s important to seek medical attention for any irregular heartbeats or unusual palpitations (racing or pounding heart).
An irregular heart rhythm is called an arrhythmia. In ATTR-CM, arrhythmias may occur when blood backs up and increases the pressure in the heart. Amyloid deposits may also disrupt the heart’s electrical conduction system. Healthcare providers may suspect ATTR-CM in people who have an arrhythmia without a known cause.
The most common type of arrhythmia in ATTR-CM is called atrial fibrillation (AFib). Between 40 percent and 60 percent of people have AFib at the time they’re diagnosed with ATTR-CM.
Common AFib symptoms include:
Untreated AFib can increase the risk of stroke. This life-threatening condition occurs when a blood clot blocks blood flow to the brain.
Spinal stenosis is a condition in which the space around the spinal cord narrows, often putting pressure on the nerves. In ATTR-CM, the abnormal TTR protein can be deposited in the ligaments of the lumbar spine (lower back), making them thicker and causing the narrowing.
Spinal stenosis sometimes appears before any heart-related symptoms, making it an early warning sign, especially in people with wild-type ATTR-CM.
Symptoms of lumbar spinal stenosis include:
Carpal tunnel syndrome causes wrist pain and weakness. This condition is usually linked to repetitive hand movements, but it can also signal underlying conditions such as ATTR-CM. The TTR protein can build up in the carpal tunnel, the opening in the wrist where tendons and nerves pass through. The narrowed space places pressure on the median nerve, which helps control the hand.
People with carpal tunnel symptoms in both hands may be more likely to have amyloidosis, and it may be an early symptom of ATTR-CM. Researchers have found that about half of people with ATTR-CM had carpal tunnel syndrome first. The risk of an amyloidosis diagnosis is almost three times higher in people who have carpal tunnel syndrome.
Tendons are strong bands of tissues that connect muscles to bones. A tendon rupture happens when a tendon tears or pulls away from the bone, usually because of an injury.
However, people with ATTR-CM may be more likely to develop this condition when abnormal TTR protein builds up in the tendons, making them weaker. About 1 in 3 people with wild-type ATTR-CM have had a biceps tendon rupture (a tear in the tendon of the upper arm, between the shoulder and elbow).
Peripheral neuropathy refers to nerve damage that occurs outside the brain or spinal cord. TTR protein buildup in the peripheral nerves can cause pain, numbness, or an inability to tell the difference between hot and cold.
In some cases, ATTR-CM affects the autonomic nerves, which control body functions you don’t think about, such as breathing, digestion, and heart rate. This is called autonomic neuropathy. Symptoms include:
People with autonomic neuropathy may not respond as well to common heart failure medications, such as beta-blockers and ACE inhibitors. This can tell healthcare professionals that heart failure symptoms may be linked to ATTR-CM instead of a more common cause. Neuropathies are more common in people with hereditary ATTR-CM than in those with the wild-type form.
Early diagnosis and proper treatment of ATTR-CM may help slow disease progression. However, diagnosis can be difficult because the symptoms are often nonspecific — they can look like other, more common health conditions. On top of that, ATTR-CM is a rare disease, and many healthcare providers may not recognize the symptoms right away.
Guidelines known as expert consensus recommendations can help healthcare providers spot patterns of symptoms that could point to ATTR-CM. Although the symptoms can vary from person to person, these recommendations help make it easier for healthcare providers to identify when ATTR-CM may be the cause.
If you have symptoms of ATTR-CM but haven’t been diagnosed yet, talk to your cardiologist or other healthcare provider about additional testing. Early action can make a big difference.
MyAmyloidosisTeam is the social network for people with amyloidosis and their loved ones. On MyAmyloidosisTeam, members come together to ask questions, give advice, and share their stories with others who understand life with amyloidosis.
Are you or a loved one living with ATTR-CM? Were your symptoms first misdiagnosed as another type of heart disease? Share your experiences in the comments below, or start a conversation by posting on your Activities page.
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