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(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) (r(2) = 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).