Ultrasonic tissue characterization of the beating hearts of mice: Evidence of anisotropy and of hypertrophy

Abstract

New insights into the disease-altered properties of the heart may be provided through the study of genetically manipulated mice. To extend methods developed for studies of the hearts of patients to the hearts of mice, we report the observation of anisotropy of backscattered ultrasound in the parasternal short-axis view of normal mouse hearts, the cyclic variation of backscatter in normal hearts, and alterations of that pattern of cyclic variation in hypertrophic hearts. Echocardiographic images were obtained using a clinical imaging system with a nominal 13-MHz linear array. In seven wild-type mice the anisotropy of mid-myocardial apparent backscatter arising from the angle of insonification relative to the local fiber orientation in the short-axis view was consistent with that observed previously in the hearts of healthy human volunteers. The magnitude of the cyclic variation of backscatter from the hypertrophic hearts of nine mice subjected to neonatal aortic banding was significantly less than that obtained from eight control, sham-operated mice. This study lays the groundwork for subsequent investigations in which genetically manipulated mice will be measured in order to clarify the mechanisms of altered ultrasonic scattering and attenuation of the disease-altered myocardium in the presence of myocardial anisotropy. [Work supported by NIH R37HL40302.]