Infiltrative cardiomyopathy: when abnormal deposits stiffen the heart muscle

In a healthy heart the muscle relaxes between beats so the chambers can fill. The NHS describes restrictive cardiomyopathy as a rare condition in which the walls of the main chambers become stiff and rigid and cannot relax properly after contracting, so the heart cannot fill with enough blood. This can cause heart failure symptoms such as breathlessness, tiredness and ankle swelling, and heart rhythm problems.

Infiltrative describes one way this can happen: abnormal material gets into, or infiltrates, the muscle. The pages used for this guide describe the individual causes rather than the umbrella term, and the main ones named are amyloidosis, iron overload from haemochromatosis and sarcoidosis. The NHS notes that in many people with restrictive cardiomyopathy the cause is unknown, although sometimes it is inherited.

The causes below are those described by NHS and Cardiomyopathy UK pages. Each is rare, and each has its own pathway.

The NHS says amyloidosis is a group of rare conditions where a protein called amyloid builds up in the body and can affect organs including the heart, kidneys, liver, nerves and digestive system. It lists several types: AL amyloidosis (a problem with the bone marrow, sometimes linked with myeloma), AA amyloidosis (long-term inflammatory or infectious disease), hereditary ATTR amyloidosis (an inherited genetic condition), wild-type ATTR amyloidosis (develops with age, usually affecting men over 75) and beta-2 microglobulin amyloidosis (long-term dialysis).

When the heart is affected, the NHS says symptoms can include a fast or slow heartbeat or chest pain, along with tiredness, shortness of breath and swollen feet or legs. Cardiomyopathy UK lists breathlessness, palpitations, swelling in the ankles, legs or tummy, fatigue, chest pain and feeling light-headed or faint. The NHS adds that symptoms can be caused by many other conditions and that it is important to see a GP.

Cardiomyopathy UK says some people with restrictive cardiomyopathy have no symptoms or very mild ones, but over time the restricted function can lead to heart failure. Symptoms it lists are tiredness, shortness of breath (even at rest) and swelling in the abdomen or ankles. Because symptoms can be subtle, diagnosis may be difficult.

For heart failure symptoms, the NHS advises seeing a GP, getting urgent advice if breathless lying down or after everyday activity or suddenly gaining weight, and calling 999 for severe difficulty breathing, pale blue or grey lips or skin, or someone who has passed out and is not responding normally. Chest pain should always be taken seriously: the NHS lists it among amyloidosis symptoms, and a heart attack is an emergency.

The NHS says amyloidosis is often hard to diagnose because symptoms vary and resemble other conditions. It lists blood and urine tests; an ECG, echocardiogram or MRI to check the heart and other organs; a biopsy; a SAP scan to show where amyloid has built up; and genetic testing for hereditary types. Cardiomyopathy UK lists blood tests, an echocardiogram, ECG, cardiac MRI and a DPD scan, which uses a tracer to detect amyloid in the heart, and says genetic testing may be recommended if hereditary ATTR is suspected.

For restrictive cardiomyopathy more generally, Cardiomyopathy UK explains that echocardiography is one of the most widely used tests in cardiology and gives information on heart size and shape, pumping capacity and how well the heart relaxes. For iron overload, treatment of the underlying haemochromatosis is given alongside heart treatment.

The NHS says that there is no cure for amyloidosis but some types can be managed well, and that for some people it eventually leads to organs such as the heart or kidneys no longer working properly. Cardiomyopathy UK says restrictive cardiomyopathy cannot be cured and that treatment may include medication, implantable devices, surgery and lifestyle management.

For cardiac amyloidosis Cardiomyopathy UK lists heart failure medicines (including an SGLT2 inhibitor such as dapagliflozin or empagliflozin, and loop diuretics such as furosemide or bumetanide), beta blockers for heart rhythm, medicines that stabilise the TTR protein (tafamidis and acoramidis), gene silencers (vutrisiran and eplontersen) and, for some people, heart or liver transplant. The NHS says AL amyloidosis may be treated with chemotherapy or a stem cell or bone marrow transplant. For haemochromatosis, Cardiomyopathy UK says the symptoms of cardiomyopathy are treated as well as the underlying iron overload. Which of these are available to a given person depends on the type and on specialist assessment.

The NHS notes that if you have amyloidosis your care team will pass information to the National Congenital Anomaly and Rare Disease Registration Service, and that you can opt out at any time. It lists Myeloma UK and the ATTR Amyloidosis Patients Association for information. Cardiomyopathy UK runs an online support group for people with ATTR cardiac amyloidosis and their families, together with Amyloidosis UK.

Day to day, much of the advice mirrors that for heart failure in general: take medicines as prescribed, weigh yourself regularly, stay as active as your team advises and report new swelling or breathlessness promptly. The NHS says heart failure symptoms can vary from day to day, and that talking therapies are available if the diagnosis feels overwhelming.

Infiltrative heart disease is rare, so assessment tends to be concentrated in cardiology departments and national amyloidosis centres on the NHS. A private cardiologist can arrange initial heart scans. Ask your GP or cardiologist which centre is coordinating your care, and who to contact if symptoms change.