Echocardiography in Mice

Abstract

Murine models have been utilized with increasing frequency mainly due to availability of genetically engineered models. With advancement in high spatial and temporal resolution, echocardiography is used extensively for the evaluation of cardiovascular function in murine models of cardiovascular disease. This review summarizes the general applications and methods involved in echocardiography used to study mouse models for cardiovascular research, based on 20 years of experience in our laboratory. The goal of this article is to provide a practical guide to the use of echo techniques in mice to evaluate cardiac systolic and diastolic function.

Figure 1

Diagrams for basic mouse echocardiography views. Panel A shows the position and direction (small arrow) of probe (upper left) for LV long-axis view (upper right). Panel B demonstrates the position and direction (small arrow) of probe (lower left) for LV short-axis view (lower right). LA=left atrium, AO=aorta.

Figure 2

Images of echocardiographic measurements in mice. (A) LV M-mode, allows for assessment of LV systolic function. (IVSd, LVIDd, PWd and IVSs, LVIDs, PWs are LV interventricular septum thicknesses, LV internal dimensions and LV posterior wall thicknesses at diastole and systole, respectively.) (B) Doppler of transmitral inflow most often used for evaluation of LV diastolic function. (E and A are peak velocities at early and late filling respectively. IVRT and IVCT are isovolumetric relaxation and contraction time. ET is LV ejection time.) (C) Tissue Doppler waveform obtained in LV posterior wall, used for assessing regional wall motion abnormality. (Ea and Aa were two waveforms at early and late diastolic phases. Sa is the peak wall motion velocity in systole.)

Figure 3

Comparing fractional shortening (FS) in two strains of mice (FVB, C57BL/6J) before and after 1, 2, and 3 weeks of pressure overload induced by transverse aortic constriction (TAC). FS was significantly decreased in C57BL mice (square) even 1 week after TAC. However, in FVB mice (triangle) FS was maintained at normal levels even after 2 weeks of TAC. *p<0.05 vs baseline. (FS=fractional shortening).

Figure 4

These are representative images and echocardiography data displaying changes in LV fractional shortening (FS) with isoproterenol and cardiomyopathy. (A) Represents a baseline image (ES=end systole, ED=end diastole). (B) After infusion with isoproterenol 0.04 μg/kg/min, LV contraction was markedly increased. (C) In transgenic mice with cardiomyopathy a clear decrease in LV contraction is observed. (D) LV FS increases with increasing doses of isoproterenol. (E) LV FS is enhanced in young transgenic mice over-expressing β1-adrenergic receptors in the heart (β1-AR Tg, gray bar) as compared to wild type (WT, white bar). However, as the mice develop cardiomyopathy with age (black bar) LV FS is found to be decreased. * p<0.05 vs WT. (Peter et al. 2007). Figure modified and used with permission.