Substudy (NCT04456582): Noninvasive Assessment of Myocardial Stiffness by 2D-SWE Ultrasound Technique (Two-dimensional Shear Wave Elastography) in Patients With Amyloidosis and Fabry Disease.

Inclusion Criteria: \- Documented diagnosis of ATTRh with and without cardiac involvement. For the definition of cardiac involvement by ATTRh, all the criteria below must be presented: * Pathogenic mutation of TTR consistent with ATTRh. * Evidence of cardiac commitment by echocardiography or nuclear magnetic resonance with measurement of the interventricular septum at the end of diastole (SIVd)\> 12mm or / and medical history of heart failure, and / or levels of troponin and / or BNP above the reference value without another more likely cause. * Amyloid deposit in cardiac or extra-cardiac tissue (eg, abdominal fat aspirate, salivary gland, connective sheath of the median nerve) confirmed by congo red staining or presence of grade 2 or 3 myocardial scintigraphy (DPD-CT) of cardiac uptake, in cases where the presence of monoclonal gammopathy of undetermined significance (MGUS) was ruled out. * In the presence of MGUS, confirmation of the TTR protein in the tissue is necessary through immunohistochemistry (IHC) or mass spectrometry. Exclusion Criteria: * Presence of another type of cardiomyopathy such as hypertension, valve or ischemic heart disease (eg, previous myocardial infarction documented with myocardial necrosis markers and electrocardiographic changes). * Presence of diseases other than cardiac amyloidosis, impairing the assessment of functional capacity, such as chronic obstructive pulmonary disease, severe arthritis or peripheral arterial disease, recent or planned orthopedic procedure during the course of the study (eg, spine surgery or under lower limbs) that impairs walking in the 6-minute test evaluation. * Acute coronary heart disease or unstable angina in the past 3 months Report of disease of the sinus or atrioventricular node with indication of a pacemaker, but with no intention of implantation. * Presence of untreated hypothyroidism or hyperthyroidism. * Previous heart, liver or other organ transplant. * Presence of neoplasia in the last 3 years, except for basal and squamous cell carcinomas of skin or cervical cancer in situ previously treated. * Presence of other medical conditions or comorbidities that, in the investigator's opinion, could interfere with the course of the study or the interpretation of the data. * Pregnancy. * History of alcohol abuse in the last 2 years or excessive daily alcohol intake (for women, more than 14 units per week; for men, more than 21 units of alcohol per week \[unit: one glass of wine (125ml) = one dose of distillate = 332.5ml of beer).