Abstract
Objective: To evaluate cardiac pump function, it is important to measure local myocardial stretchability noninvasively. The objective of this study is to clarify local myocardial stretchability on the basis of the axial strain rate (aSR) on the ultrasonic beam obtained by the phase-difference tracking method with high-frame-rate ultrasonic imaging. Subjects and Method: Twenty subjects with normal heart and 2 patients with heart disease (anterior septal infarction and dilated cardiomyopathy) participated in this study. Ultrasonic RF signals from the interventricular septum (IVS) and left ventricular posterior wall (LVPW) were obtained at a frame rate of 500–600 Hz, and the phase-difference tracking method was applied to calculate the aSR on the beam axis. The colored aSR was superimposed on the M-mode echocardiography to represent the spatial distribution of aSR. Results: In the healthy subjects, contraction and relaxation of the myocardium transited from the right ventricular side to the left ventricular side in the IVS, and from the epicardial side to the endocardial side in the LVPW. In addition, contraction and relaxation in the LVPW proceeded from the apex to the base of the left ventricle. The distribution of aSR was nonuniform, and the distribution pattern was classified into five types: spotted, multilayered, toned, layered, and repetitive. In the patients with heart disease, the absolute value of aSR was small and the distribution was uniform. Conclusion: This method precisely shows the characteristics of myocardial stretchability and it can provide important information on cardiac pump function.
