Signs of ATTR-CM

What Is ATTR-CM?

The transthyretin protein is produced mainly by the liver and plays a role in transporting thyroid hormone and vitamin A throughout the body. In ATTR-CM, this protein becomes unstable, misfolds, and clumps together into fibrous deposits that infiltrate the heart muscle. Over time, the heart walls thicken and become stiff, making it harder for the heart to fill with and pump blood effectively.

There are two main forms of ATTR-CM. The hereditary form is caused by an inherited genetic mutation in the transthyretin gene. The wild-type form occurs without a known genetic mutation and is associated with the natural aging process. Both forms share many of the same signs and symptoms, though the hereditary type can appear earlier in life.

Who Is Most Commonly Affected?

Wild-type ATTR-CM predominantly affects older adults, particularly men over the age of 60. It has historically been considered rare, but growing awareness and improved diagnostic tools suggest it may be significantly underdiagnosed.

The hereditary form can affect both men and women at younger ages, depending on the specific genetic variant involved. Certain variants are more prevalent in people of West African ancestry, making awareness particularly important within that population.

Early Warning Signs

Shortness of Breath

One of the earliest and most common symptoms of ATTR-CM is breathlessness during activities that previously caused no difficulty. As the condition progresses, shortness of breath may occur even at rest or while lying flat, often forcing a person to sleep with extra pillows to breathe more comfortably. This happens because the stiffened heart struggles to pump blood efficiently, leading to fluid backing up into the lungs.

Fatigue and Weakness

Persistent, unexplained tiredness is a hallmark symptom. People with ATTR-CM often describe feeling exhausted after minimal physical effort. This occurs because the heart cannot deliver enough oxygen-rich blood to meet the body's demands. This kind of fatigue can be easily dismissed as a normal part of aging, which is one reason the condition is frequently overlooked.

Swelling in the Legs, Ankles, and Feet

Fluid retention, known medically as edema, is another common early sign. When the heart is not pumping effectively, fluid can accumulate in the lower limbs, causing noticeable puffiness or swelling in the legs, ankles, and feet. Clothing or shoes may feel tighter than usual, particularly at the end of the day.

Cardiovascular Signs

Irregular Heartbeat

ATTR-CM is frequently associated with abnormal heart rhythms, known as arrhythmias. Atrial fibrillation — a condition where the upper chambers of the heart beat irregularly — is particularly common. People may notice a fluttering, pounding, or racing sensation in the chest, or they may have no awareness of the rhythm problem at all, with it only being detected on an electrocardiogram (ECG).

Dizziness and Fainting

Some individuals with ATTR-CM experience dizziness, lightheadedness, or even fainting episodes. These can result from the heart's reduced ability to maintain adequate blood pressure and blood flow, particularly when a person stands up quickly. This drop in blood pressure upon standing is called orthostatic hypotension.

Low Blood Pressure

Despite the thickening of the heart walls, people with ATTR-CM often have low or dropping blood pressure rather than high blood pressure. This may seem counterintuitive, but it reflects the reduced pumping capacity of the heart and the involvement of the nervous system in regulating blood pressure. Doctors may notice that blood pressure medications previously prescribed for other conditions are suddenly causing the pressure to drop too low.

Non-Cardiac Clues That May Appear First

One of the most distinctive and clinically important aspects of ATTR-CM is that several non-heart-related conditions often appear years before the cardiac symptoms. Recognizing these clues can be a critical step in reaching an earlier diagnosis.

Carpal Tunnel Syndrome

Carpal tunnel syndrome — numbness, tingling, and pain in the hands and wrists caused by pressure on the median nerve — occurs far more frequently in people who later develop ATTR-CM than in the general population. When both hands are affected, or when carpal tunnel syndrome requires surgical treatment in a person over the age of 50, it may be a signal worth investigating further in the context of amyloid disease.

Spinal Canal Narrowing (Lumbar Spinal Stenosis)

Amyloid deposits can accumulate in the tissues of the spine, causing narrowing of the spinal canal. This leads to back pain, leg pain, numbness, or weakness, particularly when walking or standing. Many patients have undergone spinal surgery for this condition before eventually being diagnosed with ATTR-CM. Pathological examination of tissue removed during spinal surgery sometimes reveals the presence of amyloid deposits, offering an important early clue.

Peripheral Neuropathy

The hereditary form of ATTR-CM is particularly associated with damage to the peripheral nerves — the nerves outside the brain and spinal cord. Symptoms include tingling, burning pain, or numbness that often begins in the feet and gradually moves upward. This nerve involvement can also affect automatic body functions such as digestion, bowel habits, and sexual function.

Gastrointestinal Symptoms

Many people with ATTR-CM, especially those with the hereditary form, experience digestive problems such as nausea, alternating constipation and diarrhea, unexplained weight loss, or a feeling of fullness after eating very little. These symptoms result from amyloid deposits affecting the nerves that control gut function.

Eye Problems

Some individuals with the hereditary form of ATTR-CM develop abnormal deposits in the fluid-producing structures of the eye. This can occasionally lead to changes in vision or be detected during a routine eye examination. Eye involvement is not a feature of the wild-type form.

Signs Detected During Medical Examination

Thickened Heart Walls on Imaging

One of the most important signs that a doctor may detect is the thickening of the heart's walls, particularly the wall between the two lower chambers (the interventricular septum). This is typically found during an imaging scan of the heart, such as an echocardiogram — an ultrasound of the heart. The pattern of thickening in ATTR-CM has a characteristic appearance that can help distinguish it from other causes of heart wall thickening.

A "Sparkling" or "Granular" Appearance on Echocardiogram

When viewed on an echocardiogram, the heart muscle in people with amyloid deposition may appear unusually bright or display a distinctive texture sometimes described as granular or sparkling. While not a definitive diagnostic criterion on its own, this finding can alert a cardiologist to investigate further for amyloid disease.

ECG Findings That Don't Match the Echo

In many types of heart disease, a thickened heart wall corresponds to increased electrical voltage on an electrocardiogram. In ATTR-CM, something unusual occurs: the ECG typically shows low voltage or normal voltage, even though the heart walls are significantly thickened. This mismatch between the ECG and the echocardiogram is a well-recognized red flag that prompts further investigation.

Elevated Biomarkers in the Blood

Routine blood tests may reveal elevated levels of certain proteins that the heart releases when it is under stress or sustaining injury. While these markers are not specific to ATTR-CM alone, they can support the clinical picture when combined with other findings and help doctors assess the severity and progression of the condition over time.

Signs in Special Populations

Older Men With "Unexplained" Heart Failure

Heart failure in older men — particularly those over 70 — that does not have a clear explanation such as coronary artery disease or high blood pressure should raise suspicion for ATTR-CM. As diagnostic awareness has grown, more cases are now being identified in elderly patients who were previously told they had an atypical or unexplained form of heart failure.

People With African Ancestry

A specific genetic variant that is more prevalent among people of West African descent is associated with a higher risk of hereditary ATTR-CM. Studies suggest that this variant may affect a notable proportion of African American individuals. Awareness within this group is especially important because the condition may be underdiagnosed due to historical disparities in access to specialist cardiac care and genetic testing.

How Is It Diagnosed?

Diagnosis typically involves a combination of imaging studies, blood and urine tests, and sometimes a bone scan using a specialized imaging agent. This type of scan has become an important non-invasive tool for identifying certain forms of ATTR-CM without the need for a tissue biopsy. In some cases, a biopsy of heart tissue or fat tissue from the abdomen may still be used to confirm the presence of amyloid deposits.

Genetic testing is recommended for all individuals diagnosed with ATTR-CM to determine whether the hereditary form is present. This information is also valuable for other family members who may wish to know their own risk.

Why Early Recognition Matters

ATTR-CM is a progressive disease, meaning it worsens over time if not addressed. The earlier the condition is identified, the better the opportunity to manage symptoms, slow progression, and reduce the risk of serious complications such as severe heart failure or life-threatening arrhythmias. Early recognition also allows for supportive care strategies that can improve quality of life and help plan for future health needs.

Raising awareness — both among the public and within the medical community — is essential. Many people live with ATTR-CM for years without knowing it, navigating a series of specialists and diagnoses that never quite explain all their symptoms. A clearer understanding of this condition's signs can help change that outcome.

When to See a Doctor

Anyone experiencing unexplained shortness of breath, persistent fatigue, leg swelling, or irregular heartbeat should seek medical evaluation. If these cardiac symptoms are combined with a history of carpal tunnel syndrome requiring surgery, spinal stenosis, unexplained digestive problems, or nerve-related symptoms in the hands or feet, it is worth specifically asking a healthcare provider whether amyloid heart disease might be a possibility.

Specialist referral to a cardiologist with experience in heart failure or amyloid disease may be appropriate in many cases. Early testing can confirm or rule out ATTR-CM and guide next steps in care.

Summary of Key Signs at a Glance

• Shortness of breath, especially during activity or when lying flat
• Persistent, unexplained fatigue and reduced exercise tolerance
• Swelling of the legs, ankles, or feet
• Irregular or rapid heartbeat (palpitations)
• Dizziness or fainting, particularly upon standing
• Low or dropping blood pressure
• History of carpal tunnel syndrome in both hands or requiring surgery
• Lumbar spinal stenosis with back and leg symptoms
• Tingling, numbness, or burning pain in the feet or hands
• Unexplained digestive problems or weight loss
• Thickened heart walls seen on a cardiac imaging scan
• Mismatch between ECG voltage and echocardiogram findings
• Elevated cardiac biomarkers in blood tests without clear cause