| Abstract: | BACKGROUND: The myocardial bulk modulus has been described as the constitutive properties of the left ventricular (LV) wall and is measured as rho V2 (rho = density, V = sound speed) using acoustic microscopy. HYPOTHESIS: The study was undertaken to assess the relationship between the myocyte bulk modulus and transmitral inflow patterns in patients with pressure-overload LV hypertrophy (LVH) and cardiac amyloidosis (AMD). METHODS: In 8 patients with LVH, 8 with AMD, and 10 controls without heart disease, the transmitral inflow pattern was recorded by Doppler echocardiography before death, and myocardial tissue specimens were obtained at autopsy. The tissue density and sound speed in the myocytes were measured by microgravimetry and acoustic microscopy, respectively. The diameters of the myocytes were measured on histopathologic specimens stained by the elastica Van Gieson method. RESULTS: In the subendocardium, the myocyte bulk modulus was larger in LVH (2.98 x 10(9) N/m2, p < 0.001) and smaller in AMD (2.61 x 10(9) N/m2, p < 0.001) than in the controls (2.87 x 10(9) N/m2). The myocyte diameter in LVH (26 +/- 1 microns) was larger than that in the control (21 +/- 1 microns, p < 0.001) and AMD (20 +/- 1 microns, p < 0.001). The bulk modulus in the subendocardial myocyte significantly correlated with the deceleration time (DT) of the early transmitral inflow (r = 0.689, p = 0.028 in control, r = 0.774, p = 0.024 in LVH, and r = 0.786, p = 0.021 in AMD). CONCLUSION: The changes in the myocyte elasticity as represented by the bulk modulus were limited to the subendocardial layers and may be related to relaxation abnormalities in LVH and a reduction in LV compliance in AMD. |
