Tissue characterization in cardiac amyloidosis: a joint consensus document by the gruppo di studio di cardiopatologia (SIAPEC) and the SIC/ANMCO Italian cardiac amyloidosis network (RIAC).

Cardiac amyloidosis (CA) is an infiltrative cardiomyopathy caused by the accumulation of protein fibrils with an abnormal 3D configuration in the myocardium. The introduction of targeted therapies for the two most common forms, light-chain amyloidosis (AL) and transthyretin amyloidosis (ATTR), has made prompt recognition and accurate typing of the amyloid protein indispensable. Although in some ATTR cases a diagnosis can be reached with noninvasive imaging methods, diagnostic confirmation by peripheral or endomyocardial biopsy remains fundamental for many patients with ATTR and for all those with AL or rarer CA variants. The available typing complementary techniques are immunohistochemistry, immunofluorescence, immune electron microscopy, and mass spectrometry, each with specific strengths and limitations. This review describes the current indications for tissue analysis and compares the options for amyloid typing, with the aim of providing guidance relevant to clinical practice.