Abstract Body: Introduction: Impaired left ventricular (LV) relaxation, a consequence of left ventricular diastolic dysfunction (LVDD), is a common sequela of cardiometabolic diseases. While separate endeavors have been devoted to studying the mechanical and metabolic mechanisms of diastolic function, the physiological link across mechano-metabolic cues governing relaxation remains understudied. Herein, we present a platform for measuring mechano-metabolic indices of diastolic function in mice through in-vivo echocardiography, followed by ex-vivo benchtop testing of mechanics and energetics.
Methods: Male, 8-10-week-old wild-type mice were used. Early transmitral flow to mitral annular tissue velocity ratio (E/e’), measured by Doppler imaging, was used to assess LV relaxation. The LV free wall (LVFW) was harvested from the mice and immediately placed in PBS at 1°C. Mechanical testing was performed to measure stiffness (n = 4). Additionally, energetics were quantified by homogenizing 10 mg of LVFW tissue using buffer A and analyzing the supernatant ATP concentration (n = 4).
Results: A bias in passive stresses towards the circumferential direction, in comparison to the longitudinal direction, was noted at various stages of equibiaxial stretching (Fig. 1A). A similar anisotropic behavior was confirmed via LVFW stiffness (Fig. 1B). A consistent spread in E and e’ was maintained in all mice, evidenced via similar standard deviation (Fig. 1C). Baseline diastolic function was established using the E/e’ ratio (Fig. 1D), and the average basal ATP levels in mice was measured as 1.75 ± 0.58 nmol (Fig. 1E).
Conclusion: The integration between in-vivo echocardiography and ex-vivo mechanical testing and metabolic assays was established in mice. This platform will enable us to determine the relationship between mechanical and metabolic alterations in LVDD, thereby optimizing patient-specific therapies based on these integrated measures of diastolic function.