Cardiac amyloidosis is a condition in which abnormal misfolded proteins (called amyloid fibrils) accumulate within the heart muscle, disrupting its structure and function. As amyloid deposits build up in the myocardium, the heart walls become abnormally thick and rigid, impairing the heart’s ability to fill during diastole and, in advanced disease, its ability to pump during systole. The resulting heart failure is called restrictive cardiomyopathy, and the condition is sometimes described informally as ‘stiff heart syndrome’.
There are two main types. AL (light-chain) amyloidosis is caused by abnormal plasma cells producing misfolded immunoglobulin light chains, which accumulate in the heart and other organs. It is associated with haematological conditions such as multiple myeloma and is treated with chemotherapy. ATTR (transthyretin) amyloidosis is caused by misfolded transthyretin, a protein produced by the liver. It has a hereditary form (particularly common in people of West African ancestry, caused by a specific gene mutation) and a wild-type form (occurring predominantly in older men without a genetic cause).
Cardiac amyloidosis presents with heart failure symptoms (breathlessness, fatigue, oedema) and is frequently misdiagnosed for years. Characteristic features include low-voltage ECG complexes despite thickened heart walls on echocardiography, a specific pattern on cardiac MRI (late gadolinium enhancement), and a positive nuclear scintigraphy scan (using DPD or PYP tracers) that can diagnose ATTR amyloidosis non-invasively with high accuracy.
New treatments for ATTR amyloidosis, including tafamidis (which stabilises the transthyretin protein and significantly slows progression), have been approved in the UK and improve outcomes. Cardiac amyloidosis is an increasingly recognised cause of unexplained heart failure, arrhythmia, and aortic stenosis; patients with unexplained ventricular thickening or low-voltage ECG should be investigated for it.
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