Instantaneous Pressure-Volume Relationships and Their Ratio in the Excised, Supported Canine Left Ventricle

Abstract

We have previously shown in the normally ejecting canine left ventricle that E ( t ), the time-varying ratio of instantaneous pressure, P ( t ), to instantaneous volume, V ( t ), is little affected by end-diastolic volume or aortic pressure. The present study on an excised, supported canine heart preparation indicates that the thesis on E ( t ) is also valid for either totally isovolumic or auxobaric beats. Intraventricular volume was measured more accurately than it was in the previous study by a new volumetric system. Regression analysis of the data showed that the instantaneous pressure-volume relationship could be approximated by the equation P ( t ) = E ( t ).[ V ( t ) - V d ], where V d is an empirical constant, over a wide range of intraventricular volume. Similar E ( t ) curves were obtained from both isovolumic and auxobaric beats for a given contractile state. When the contractile state of the preparation was enhanced by a constant-rate infusion (0.2 µg/min) of norepinephrine or isoproterenol into the coronary artery, the peak magnitude of E ( t ) increased 63% from 3.6 mm Hg/ml and the time to peak E ( t ) shortened 10% from 175 msec. We conclude that the present investigation substantiates our earlier study which established a link between E ( t ) and the contractile state of the heart.

Multiscale model of the human cardiovascular system: Description of heart failure and comparison of contractility indices

“…The heart contraction is often described with ad hoc models, like the time-varying elastance model [1,2,3]. Such macroscopic models are not based on the cardiac tissue Email address: sarah.kosta@ulg.ac.be (S. Kosta,) properties and cannot reproduce behaviors that arise from the microscopic scale.…”

Laterality in Direct and Indirect Inotropic Effects of Sympathetic Stimulation in Isolated Canine Heart.

“…In an isolated cross-circulated canine heart, we can precisely measure left ventricular volume and pressure and therefore estimate E es , which has been known to be a load insensitive index of left ventricular contractility [5][6][7][8][9]. Although direct actions of pharmacological agents on the heart can be investigated without autonomic nerves, indirect actions of pharmacological agents on the heart through the modulation of the autonomic nervous system cannot be analyzed by ordinary isolated canine heart preparation.…”

“…Although previous studies investigated sympathetic regulation of left ventricular function and HR [1][2][3][4], the load dependency of the indexes of ventricular contractility used in these studies, such as dP/dt (the first derivative of pressure waveform), ejection fraction, and stroke volume, makes it difficult to quantitatively compare the relative contribution of the direct and indirect inotropic effects. On the other hand, left ventricular end-systolic elastance (E es ), which is the slope of the end-systolic pressurevolume relationship, has been shown to be a load-insensitive index of ventricular contractility [5][6][7][8][9]. Although the precise estimation of E es can be achieved in an isolated cross-circulated canine heart preparation, because the heart was denervated during the isolation procedure makes this preparation inappropriate for investigating its autonomic regulation.…”

The pressure-volume and stiffness-pressure relations in the isolated rabbit left ventricle.

“…One of the reasons has been the difficulty in controlling the intraventricular volume. Recently, SUGA and SAGAWA (1974) overcame this difficulty by adopting the intraventricular balloon method to the isolated dog heart. OKUYAMA (1983) has determined the hyperbolic relation between pressure and ejection velocity in the rabbit ventricle and has successfully shown the quantitative interrelation of force-velocity with ventricular wall muscle.…”