Quantitative Tissue Characterization of Valvular Disease Based Upon Acoustic Properties Measured by High-frequency Ultrasound

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The purpose of the present study was to measure tissue sound speed and ultrasonic attenuation of cardiac valve using acoustic microscopy with high frequency ultrasound. Myocardial and valvular tissue density positively correlated with the tissue sound speed measured by acoustic microscopy. Therefore, according to the equation K=ρ c^2, where K is the bulk modulus, ρ is the density, and c is the sound speed of tissue, myocardial and valvular tissue sound speed data enables us to evaluate tissue elasticity without measuring tissue density directly. In order to assess die physical properties of mitral valve tissue by evaluating the sound speed of the mitral valve tissue in cardiac amyloidosis, mitral valve specimens were obtained at autopsy from 20 control subjects without cardiovascular disease and from 20 patients with cardiac amyloidosis. The tissue sound speed was measured using acoustic microscopy. The patients with cardiac amyloidosis showing moderate mitral regurgitation demonstrated the greater reduction in the tissue sound speed than the patients with cardiac amyloidosis showing mild mitral regurgitation. The data suggest that the changes in physical properties of the MV tissue may be one of causes of mitral regurgitation in cardiac amyloidosis. Thus, tissue sound speed of cardiac valve measured by acoustic microscopy provides information regarding quantitative tissue characterization and pathophysiology in valvular disease.