Quantification of cardiac pumping mechanics in rats by using the elastance-resistance model based solely on the...

The cardiac pumping mechanics can be characterized by both the maximal systolic elastance (E_max) and theoretical maximum flow (Q_max), which are generated using an elastance-resistance model. The signals required to fit the elastance-resistance model are the simultaneously recorded left ventricular (LV) pressure and aortic flow (Q^m), followed by the isovolumic LV pressure. In this study, we evaluated a single-beat estimation technique for determining the E_max and Q_max by using the elastance-resistance model based solely on the measured LV pressure and cardiac output. The isovolumic LV pressure was estimated from the measured LV pressure by using a non-linear least-squares approximation technique. The measured Q^m was approximated by an unknown triangular flow (Q^tri), which was generated by using a fourth-order derivative of the LV pressure. The Q^tri scale was calibrated using the cardiac output. Values of E_max^triQ and Q_max^triQ obtained using Q^tri were compared with those of E_max^mQ and Q_max^mQ obtained from the measured Q^m. Healthy rats and rats with chronic kidney disease or diabetes mellitus were examined. We found that the LV E_max and Q_max can be approximately calculated using the assumed Q^tri, and they strongly correlated with the corresponding values derived from Q^m (P < 0.0001; n = 78): E_max^triQ = 51.9133 + 0.8992 × E_max^mQ (r² = 0.8257; P < 0.0001); Q_max^triQ = 2.4053 + 0.9767 × Q_max^mQ (r² = 0.7798; P < 0.0001). Our findings suggest that the proposed technique can be a useful tool for determining E_max and Q_max by using a single LV pressure pulse together with cardiac output.