The main focus of this work is the echogenicity of a 3D-printed synthetic composite material that mimics the acoustic properties of cardiac biological tissues to provide ultrasound images similar to those obtained during interventional cardiology procedures. The 3D-printed material studied is a polymer-based composite with a matrix-inclusion microstructure, which plays a critical role in ultrasound response due to ultrasound-microstructure interaction at the involved medical echography wavelengths. Both numerical simulations and experimental observations are carried out to quantitatively establish the relationship between the 3D-printed microstructure and its ultrasonic echogenicity, considering different microstructure characteristics, namely area fraction and size of the inclusion, and its actual printed shape. A numerical evaluation based on finite element modeling is carried out to characterize the acoustic properties of the 3D-printed synthetic tissue: phase velocity, attenuation coefficient, and B-mode ultrasound images. Moreover, a morphological experimental study of the shape of the real 3D-printed inclusions is carried out. It shows a significant deviation of the final printed inclusions compared to the input spherical shape delivered to the 3D printer. By simulating and comparing numerically generated microstructures and 3D-printed real microstructures, it is shown that the actual shape of the inclusion is significant in the scattering of the ultrasonic wave and the echogenicity of the printed material.