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

To quantitate the contractile mechanics of the heart, the ventricle is considered an elastic chamber with known end-systolic elastance (E ). E 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 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^triQ obtained using Q^tri were compared with those of E^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^mQ and E^triQ. A significant regression line for E was observed (P < 0.0001): E^triQ = 2.6214 + 1.0209 × E^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.