Quantification of contractile mechanics in the rat heart from ventricular pressure alone

Abstract

To quantitate the contractile mechanics of the heart, the ventricle is considered an elastic chamber with known end-systolic elastance (E_es). E_es can be calculated from a single pressure-ejected volume curve, which requires simultaneous records of left ventricular (LV) pressure and the aortic flow (Q^m). In clinical settings, it is helpful to evaluate patients’ cardiac contractile status by using a minimally invasive approach to physiological signal monitoring, wherever possible, such as by using LV pressure alone. In this study, we evaluated a method for determining E_es on the basis of the measured LV pressure and an assumed aortic flow with a triangular wave shape (Q^tri). Q^tri was derived using a fourth-order derivative of the LV pressure to approximate its corresponding Q^m. Values of E_es^triQ obtained using Q^tri were compared with those of E_es^mQ obtained from the measured Q^m. Healthy rats (NC; n = 28) and rats with type 1 diabetes (DM; n = 26) and chronic kidney disease (CKD; n = 20) were examined. The cardiodynamic conditions in both the DM and CKD groups were characterized by a decline in E_es^mQ and E_es^triQ. A significant regression line for E_es was observed (P < 0.0001): E_es^triQ = 2.6214 + 1.0209 × E_es^mQ (r² = 0.9870; n = 74). Our finding indicates that the systolic pumping mechanics of the heart can be derived from a single LV pressure recording together with the assumed Q^tri.