title: Single-beat estimation of the ventricular pumping mechanics in terms of the systolic elastance and resistance.
abstract: An elastance-resistance model has long been used to assess the systolic mechanical behavior of the ventricular pump under an in situ, open-chest experiment. However, there is difficulty in the clinical application of such a model because of the required isovolumetric signal that is obtained by occluding the ascending aorta in diastole. In this study, we determine the characteristics of an elastance-resistance model in the absence of isovolumeric measurement to quantify the physical properties of the left ventricle. A high-fidelity multisensor catheter was used to record the left ventricular pressure and ascending aortic flow in nine anesthetized, closed-chest dogs. The isovolumetric pressure was estimated from the instantaneous pressure of an ejecting contraction by a curve-fitting technique. Thus, the parameters in the characterization of systolic pumping mechanics could be inferred by the use of fitting this elastance-resistance model. The results showed that the maximal systolic elastance was 7.3 +/- 2.8 mmHg and theoretical maximum flow was 494 +/- 194 ml s-1. These data were compatible with other reports in the literature. Moreover, in every dog studied the maximal systolic elastance was smaller than the end-systolic elastance which was determined by using the end-systolic pressure-volume relation. We suggested that an elastance-resistance model with the estimated isovolumetric pressure has the potential to measure the intrinsic systolic mechanics of the left ventricle in a closed-chest cardiovascular system.
authors.affiliation: Department of Physiology, College of Medicine, National Taiwan University, Taipei.
authors.forename: K C
authors.initials: KC
authors.lastname: Chang
authors.forename: T S
authors.initials: TS
authors.lastname: Kuo
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004285:Dogs; D004548:Elasticity; D005260:Female; D008297:Male; D008955:Models, Cardiovascular; D013599:Systole; D016277:Ventricular Function, Left / Q000502:physiology*