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 (Ees). Ees can be calculated from a single pressure-ejected volume curve, which requires simultaneous records of left ventricular (LV) pressure and the aortic flow (Qm). 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 Ees on the basis of the measured LV pressure and an assumed aortic flow with a triangular wave shape (Qtri). Qtri was derived using a fourth-order derivative of the LV pressure to approximate its corresponding Qm. Values of EestriQ obtained using Qtri were compared with those of EesmQ obtained from the measured Qm. 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 EesmQ and EestriQ. A significant regression line for Ees was observed (P < 0.0001): EestriQ = 2.6214 + 1.0209 × EesmQ (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 Qtri.

Quantification of cardiac pumping mechanics in rats by using the elastance–resistance model based solely on the measured left ventricular pressure and cardiac output

“…The levels of serum creatinine and blood urea nitrogen were determined using an autoanalyzer (Model 7070, Hitachi Electronics Co., Ltd., Tokyo, Japan). Type 1 DM was induced through a single-tail vein injection with 55 mg kg −1 streptozotocin (STZ; Sigma, St. Louis, MO, USA) in 0.1 M citrate buffer (pH 4.5; Sigma) [28]. Type 2 DM was induced by intraperitoneally administering 180 mg kg −1 nicotinamide (NA) (Sigma, St. Louis, MO, USA) 30 min before an intravenous injection of 50 mg kg −1 STZ dissolved in 0.1 M citrate buffer (pH 4.5) [15].…”

“…All the rats were provided ad libitum Purina chow and water and housed under 12-h light–dark cycles. The experiments were conducted according to the Guide for the Care and Use of Laboratory Animals, and our study protocol was approved by the Animal Care and Use Committee of the National Taiwan University [28].…”

“…The cardiodynamic variables were measured in the anesthetized rats, according to previously described general surgical procedures and methods [28]. Briefly, the rats were anesthetized with sodium pentobarbital (50 mg kg −1 ; intraperitoneal), placed on a heating pad, intubated, and ventilated using a rodent respirator (Model 131, New England Medical Instruments, Medway, MA, USA).…”

“…Using Q tri , they successfully separated the measured aortic pressure pulse into its forward and backward components. In 2017, Wang et al [28] evaluated a method for determining the slope ( E es ) of the end-systolic pressure–volume relation ( ESPVR ) on the basis of the measured LV pressure and an assumed Q tri . In their study, Q tri was derived using a fourth-order derivative of the LV (but not aortic) pressure to approximate its corresponding Q m .…”

“…The technique proposed by Sunagawa et al [26] was used to estimate the isovolumic LV pressure from the measured LV pressure. An uncalibrated Q tri was constructed from the measured LV pressure based on the method proposed by Wang et al [28]. The Q tri scale was calibrated using the cardiac output.…”