Cardiac amyloidosis is a serious but often overlooked condition in which abnormal proteins called amyloids build up in the heart muscle. Over time, these deposits stiffen the heart walls, making it harder for the heart to pump blood effectively. Because its early signs closely resemble other common heart conditions, cardiac amyloidosis is frequently misdiagnosed or detected only at an advanced stage. Knowing what to look out for can make a critical difference in getting timely treatment.
What Is Cardiac Amyloidosis?
Cardiac amyloidosis occurs when misfolded proteins accumulate in the heart tissue. The two most common types are AL amyloidosis, caused by abnormal plasma cells in the bone marrow, and ATTR amyloidosis, caused by a protein called transthyretin. ATTR amyloidosis can be either inherited (hereditary) or age-related (wild-type), with wild-type being more common in older adults.
The condition was once considered rare, but advances in diagnostic imaging and awareness have revealed that it is significantly underdiagnosed, particularly in elderly patients with heart failure or other cardiac conditions.
Why Early Detection Matters
The earlier cardiac amyloidosis is identified, the more treatment options are available to slow its progression. Newer targeted therapies have been developed specifically for ATTR amyloidosis, and prompt diagnosis can help preserve heart function and quality of life. Recognizing the warning signs is therefore an essential first step.
Key Signs of Cardiac Amyloidosis
Shortness of Breath
One of the most common and early signs of cardiac amyloidosis is shortness of breath, particularly during physical activity. As amyloid deposits stiffen the heart walls, the heart loses its ability to relax and fill with blood properly — a condition called diastolic dysfunction. This causes fluid to back up into the lungs, making breathing difficult.
As the condition progresses, breathlessness may occur even at rest or when lying flat. Many people find they need to prop themselves up with extra pillows to sleep comfortably, a sign known as orthopnea.
Swelling in the Legs, Ankles, and Abdomen
Fluid retention is a hallmark sign of heart failure caused by cardiac amyloidosis. When the heart cannot pump efficiently, fluid builds up in the lower extremities, leading to noticeable swelling in the legs, ankles, and feet. The abdomen may also become distended due to fluid accumulation around the organs.
This swelling, known as peripheral edema, often worsens throughout the day and may leave visible indentations when pressed — a symptom called pitting edema.
Fatigue and Weakness
Persistent and unexplained fatigue is another major warning sign. Because the stiffened heart struggles to deliver adequate blood and oxygen to the muscles and organs, patients often feel exhausted even after minimal exertion. Everyday tasks such as climbing stairs, walking short distances, or carrying groceries can become surprisingly draining.
This fatigue is not simply tiredness from lack of sleep. It is a deep, pervasive exhaustion that does not improve with rest and can significantly impact daily functioning.
Irregular Heartbeat (Arrhythmia)
Amyloid deposits can disrupt the heart's electrical system, leading to abnormal heart rhythms known as arrhythmias. Patients may notice palpitations — a fluttering, pounding, or racing sensation in the chest. Some may experience episodes of a rapid heartbeat (tachycardia) or an irregularly irregular rhythm known as atrial fibrillation.
Arrhythmias associated with cardiac amyloidosis can increase the risk of stroke and sudden cardiac death, making them particularly important to identify and treat.
Low Blood Pressure and Dizziness
Unlike many other heart conditions, cardiac amyloidosis can paradoxically be associated with low blood pressure rather than high. Patients may experience sudden drops in blood pressure when standing up — a condition called orthostatic hypotension — which can cause dizziness, lightheadedness, or even fainting (syncope).
This occurs because amyloid deposits can affect the autonomic nervous system, which regulates blood pressure responses. It can make standard heart failure treatments, such as certain blood pressure medications, more challenging to manage.
Carpal Tunnel Syndrome
One of the more surprising early warning signs of cardiac amyloidosis — particularly ATTR amyloidosis — is bilateral carpal tunnel syndrome. When amyloid proteins deposit in the wrist tendons, they can compress the median nerve, causing numbness, tingling, and pain in the hands and fingers.
What makes this significant is that it often appears years before heart symptoms develop. Research has shown that a notable proportion of people diagnosed with ATTR amyloidosis had a history of carpal tunnel surgery. If someone has had carpal tunnel syndrome in both wrists, especially at a younger age than typical, it may warrant further investigation.
Spinal Stenosis
Similarly, amyloid deposits in the spine can cause spinal stenosis — a narrowing of the spinal canal that leads to back pain, numbness, or weakness in the legs. Like carpal tunnel syndrome, this can be an early systemic sign that amyloid proteins are accumulating in multiple tissues, potentially including the heart.
Thickened Heart Walls (Detected on Imaging)
In many cases, cardiac amyloidosis is first suspected when imaging tests reveal an abnormally thickened heart muscle. An echocardiogram (ultrasound of the heart) may show increased thickness of the left ventricular walls — a pattern sometimes described as having a "sparkling" or granular appearance due to the protein deposits.
This finding may initially be misinterpreted as hypertrophic cardiomyopathy (thickening of the heart from high blood pressure), which is one reason why cardiac amyloidosis often goes undiagnosed. A key distinguishing feature is that in cardiac amyloidosis, the thickening is not explained by high blood pressure or other obvious causes.
Reduced Voltage on ECG Despite Thickened Walls
A classic and diagnostically important clue is what doctors call a "voltage-mass mismatch" on an electrocardiogram (ECG). In most conditions that cause thickened heart walls, the ECG shows increased electrical signals. In cardiac amyloidosis, however, the ECG often shows unusually low voltage despite the thickened walls — because the amyloid deposits interfere with the heart's electrical conduction.
This discrepancy between the physical size of the heart (as seen on imaging) and its electrical activity (as seen on ECG) is a strong indicator that amyloidosis may be the underlying cause.
Chest Pain and Angina-Like Symptoms
Some patients with cardiac amyloidosis experience chest discomfort, pressure, or tightness that can mimic angina — the chest pain associated with coronary artery disease. This can occur because amyloid deposits narrow the small blood vessels within the heart, reducing blood flow to the heart muscle itself.
Unlike typical angina, this type of chest pain may not respond well to standard treatments such as nitrates, and further evaluation is needed to determine the true cause.
Weight Loss and Poor Appetite
Unexplained weight loss and reduced appetite can accompany cardiac amyloidosis, particularly when the condition is associated with gastrointestinal involvement (more common in AL amyloidosis). The combination of a failing heart and systemic amyloid deposition can cause general malaise, nausea, and a reduced desire to eat.
Signs That Are Easily Mistaken for Other Conditions
One of the greatest challenges with cardiac amyloidosis is that many of its signs closely overlap with more common conditions. Heart failure, hypertrophic cardiomyopathy, and coronary artery disease can all produce similar symptoms. As a result, patients may be treated for years for a different diagnosis before amyloidosis is considered.
Doctors and patients alike should be particularly alert when:
• Heart failure symptoms are present but do not respond well to standard treatments.
• Thickened heart walls are found in someone without a clear cause such as longstanding high blood pressure.
• Multiple seemingly unrelated conditions are present — such as carpal tunnel syndrome, spinal stenosis, and heart failure together.
• Symptoms appear in older men, as wild-type ATTR amyloidosis disproportionately affects men over the age of 65.
Signs Specific to AL vs. ATTR Amyloidosis
Signs More Common in AL Amyloidosis
AL amyloidosis tends to progress more rapidly and can involve multiple organs simultaneously. In addition to cardiac symptoms, patients may notice a characteristic skin discoloration around the eyes called periorbital purpura (raccoon eyes), which appears as bruising without injury. An enlarged tongue (macroglossia) is another distinctive feature that, while not universal, is strongly suggestive of AL amyloidosis when present.
Kidney involvement leading to protein in the urine (proteinuria) and nerve damage (peripheral neuropathy) causing numbness or tingling in the hands and feet are also more commonly seen in AL amyloidosis.
Signs More Common in ATTR Amyloidosis
ATTR amyloidosis, particularly the hereditary form, often presents with a combination of cardiac and neurological symptoms. Peripheral neuropathy — including pain, numbness, or weakness in the limbs — is frequently reported. The hereditary form is more common in certain populations, including people of West African descent who carry the Val122Ile mutation, and Portuguese, Swedish, or Japanese descent who carry other mutations.
Wild-type ATTR amyloidosis, which is not inherited, typically affects the heart predominantly and is most common in men over 65. It may present primarily with heart failure symptoms and is increasingly being recognized as a cause of heart failure in this demographic.
When to See a Doctor
Anyone experiencing a combination of the symptoms described in this article — particularly unexplained heart failure, bilateral carpal tunnel syndrome, thickened heart walls without clear cause, or unusual patterns on an ECG — should speak with their doctor promptly. A cardiologist with experience in amyloidosis or a specialist center is ideally placed to investigate further.
Diagnostic tools used to confirm cardiac amyloidosis include echocardiography, cardiac MRI, nuclear scintigraphy (bone scan), blood and urine protein tests, and in some cases, a tissue biopsy. Getting the right diagnosis is the essential first step toward accessing the treatments that can help manage this condition.
Key Takeaways
Cardiac amyloidosis is an underdiagnosed condition that presents with a range of signs, from shortness of breath and leg swelling to carpal tunnel syndrome and low ECG voltage. Its symptoms often mimic other heart conditions, which contributes to delayed diagnosis. Awareness of the full spectrum of signs — both cardiac and non-cardiac — is crucial for identifying this condition early, when treatment options can have the greatest impact.
If you or someone you know has persistent, unexplained heart symptoms that have not responded to typical treatments, it is worth raising the possibility of cardiac amyloidosis with a healthcare professional. Early diagnosis truly can change outcomes.
