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

// Chih-Hsien Wang 1, 2 , Ru-Wen Chang 3 , Chun-Yi Chang 4 , Ming-Shiou Wu 5 , Hsien-Li Kao 5 , Liang-Chuan Lai 3 , Tai-Horng Young 6 , Hsi-Yu Yu 1 , Yih-Sharng Chen 1 and Kuo-Chu Chang 3 1 Department of Surgery, National Taiwan University Hospital, Taipei 100, Taiwan 2 Department of Surgery, National Taiwan University Hospital, Hsinchu Branch, Hsinchu 300, Taiwan 3 Department of Physiology, College of Medicine, National Taiwan University, Taipei 100, Taiwan 4 Department of Emergency Medicine, Taipei Veterans General Hospital, Chu-Tung Branch, Hsinchu 310, Taiwan 5 Department of Internal Medicine, National Taiwan University Hospital, Taipei 100, Taiwan 6 Institute of Biomedical Engineering, College of Medicine and Engineering, National Taiwan University, Taipei 100, Taiwan Correspondence to: Kuo-Chu Chang, email: kcchang1008@ntu.edu.tw Keywords: cardiac contractility; pressure-ejected volume curve; end-systolic elastance; left ventricular pressure; triangular aortic flow Received: June 20, 2017      Accepted: September 23, 2017      Published: October 10, 2017 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 ( 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 .