Non-invasive left ventricular contractility indices derived from thoracocardiography in rats

Preclinical studies of cardiac contractility in rodents are constrained by the invasiveness of current measurement techniques. We investigated whether flow-derived variables obtained by thoracocardiography (TCG), a fully non-invasive technique that does not require surgery, can serve as surrogates for dP/dt_max. Anesthetized rats were instrumented with both a TCG sensor and a left intraventricular pressure probe to provide the invasive reference. A pharmacological hemodynamic challenge was induced, and four TCG-based indices of early-systolic dynamics-peak aortic velocity (V_p), peak aortic acceleration (A_p), mean aortic acceleration (A_m), and the ratio of [Formula: see text] to time-to-peak velocity were quantified and compared with dP/dt_max. All indices increased during dobutamine infusion and decreased after DL-propranolol injection, paralleling changes in the reference measure. A_p exhibited the strongest correlation with dP/dt_max (r = 0.83, p < 0.001). This metric reflects the rapid rise in aortic flow at the onset of ejection and captures the inertial force generated by the ventricle to accelerate the proximal blood column; higher values therefore indicate a stronger contractile performance. These findings provide proof-of-concept that TCG can yield robust contractility surrogates without surgical access, enabling prescreening, longitudinal follow-up and potentially fully non-invasive hemodynamic monitoring in freely moving rodents.