Cardiac amyloidosis (CA) and Fabry disease (FD) are cardiomyopathies that cause heart failure. Despite diastolic dysfunction being markedly altered, pathophysiological mechanisms differ between diseases. While in CA there is an extracellular protein deposition, in FD there is a lysosomal accumulation and intracellular inflammation.1, 2, 3, 4 Whether myocardial stiffness (MS) in these two diseases is equally affected is unknown.

Evaluation of systolic and diastolic functions is essential for the comprehensive prognostic analysis of heart failure. The echocardiogram plays a fundamental role and is a widely used and inexpensive test, indicated for all patients with myocardial disease. Despite that, the diastolic function is incompletely evaluated. Active relaxation, a component of diastolic function, is the only one investigated in clinical practice, but not MS. Direct assessment of MS is only provided invasively.5 However, costs and feasibility preclude its common use.

MS can be evaluated quantitatively by a noninvasive ultrasound-based Shear wave imaging (SWI).6,7 This method has been widely used in liver, prostate, and thyroid pathologies, and is promising for cardiac evaluation. SWI was shown to quantify the MS accurately when compared with invasive parameters.8 Recent study confirmed the ability to quantify and differentiate MS noninvasive in healthy volunteers and hypertrophic cardiomyopathy patients.9 Another study showed marked elevated natural shear wave velocity for CA patients.10

The left ventricular myocardium is not homogenous, and the global properties of the cavity do not reflect regional tissue properties. Differences can be present between different myocardial segments. Studies to date that have evaluated cardiomyopathies have only performed SWI in the basal septal region, although it is possible to measure stiffness in other segments.11

Thus, considering the importance of myocardial stiffness in restrictive diseases, and the difficulty in differentiating diseases such as CA and FD, the possibility of detecting MS noninvasively and the ability to differentiate these diseases through these measures remains uncertain. We aimed in this study to quantify shear wave propagation speed and MS non-invasively using SWI in CA patients and to compare it with MS in patients with Fabry disease patients and a healthy volunteer population (HV).