Long-Axis Biplane Echocardiography Sensitively Detects the Progressing Functional Deterioration of Mouse Heart

Transthoracic echocardiography remains the primary non-invasive method for evaluating cardiac function.However, current echocardiographic techniques for mice (e.g. the conventional short-axis M-mode) lack sensitivity to detect subtle changes in heart performance.1 Although the modified biplane Simpson's method of discs is recommended for echocardiographic assessment in humans, 2 this approach has not been utilized in mice due to challenges in obtaining on-axis apical 4-chamber views.3 To address this limitation, we developed a novel methodology of apical 4-chamber-long-axis (A4CLAX) views.This method involves placing a 1.0-cm-diameter soft support underneath the mouse's upper abdominal region and positioning mouse on a 50°-inclined platform, allowing for transducer alignment parallel to the 4-chamber-viewing plane via subcostal imaging (Fig. 1A).Using monoplane volumes from left ventricular (LV) parasternal long-axis (PLAX) and A4CLAX tracings, we developed an equation to estimate the Simpson's PLAX/A4CLAX biplane (LAX-BP) volumes for functional analysis.All procedures were conducted following the established institutional guidelines.All data are available from the corresponding author upon reasonable request.We first assessed a group of adult wild-type (WT) C57BL/6N mice by both M-mode and LAX-BP assessments (Vevo3100, VisualSonics) and compared the results to cardiovascular magnetic resonance (CMR) imaging from the same animals.Our findings validated the assessments of volumetric LV parameters, including end-diastolic volume (EDV) and endsystolic volume (ESV), showing a high degree of agreement between LAX-BP and CMR assessments.