Myocardial stiffness assessed by real-time 3D shear wave elastography discriminates accurately ATTR from AL cardiac amyloidosis

Background Cardiac amyloidosis (CA) results from myocardial amyloid deposition, causing increased stiffness and diastolic dysfunction. Differentiating the two main types, Light-Chain (AL) and Transthyretin (ATTR), is critical: ATTR progresses slowly and responds to targeted therapies, whereas AL is rapidly progressive, directly cardiotoxic, and requires urgent chemotherapy. Currently, standard echocardiography cannot reliably differentiate AL from ATTR-CA. We hypothesized that myocardial stiffness, quantitatively assessed using transthoracic 3D shear wave elastography (3D-SWE), can distinguish between these etiologies. Methods 72 patients with confirmed CA underwent echocardiography, bone scintigraphy, biopsy, blood tests, and 3D-SWE at a Hospital (France). Ten 3D-SWE acquisitions were performed per target myocardial segments: the anterior free wall of the right ventricle (RV), the basal anteroseptal (AS) wall in the parasternal long-axis view, and the apex in the apical four-chamber view. Shear wave velocity (SWV) was quantified within a 10x16x16 mm³ myocardial volume of each segment during diastasis using ECG gating (Fig A). Results The cohort comprised 44 patients with ATTR-CA (80±7 years), 24 with AL-CA (66±10 years), and 4 with non-typable CA (87±8 years) based on standard diagnostic criteria. All patients successfully underwent 3D-SWE scanning. While standard echocardiographic parameters failed to discriminate between the AL and ATTR groups, SWV was significantly higher in ATTR-CA compared to AL-CA patients in both the AS wall (p<0.001) and RV free wall (p<0.001), though not at the apex. A multiparametric diagnostic algorithm combining patient age, NT-proBNP levels, and median SWV in the AS and RV walls successfully classified all typable patients, achieving 100% sensitivity and 100% specificity within this cohort. Conclusion Myocardial stiffness measured by 3D-SWE can accurately discriminate between ATTR and AL cardiac amyloidosis, overcoming the limitations of standard echocardiography. This non-invasive approach demonstrates excellent accuracy and holds tremendous promise as a front-line tool for expediting type-specific CA diagnosis and monitoring.Myocardial stiffness of AL and ATTR CA