Preload-induced curvilinearity of left ventricular end-systolic pressure-volume relations. Effects on derived indexes in closed-chest dogs.

Abstract

With the technical assistance of Monique LaplaceEnd-systolic pressure-volume relations (ESPVRs) were analyzed in 10 closed-chest autonomically blocked dogs before and after volume loading that restored end-diastolic volume to its value measured in the control conscious state isolated canine left ventricles.6 Thus, these factors may produce a curvilinearity of ESPVR when the range of loading modifications is large. The goal of our study was to determine the extent to which ESPVRs are curvilinear during loading modifications induced either by an increase in afterload and aortic impedance (aortic constriction) or by a decrease in preload and afterload (venal caval occlusion) before and after volume loading in closedchest dogs with autonomic blockade to avoid cardiovascular reflexes that significantly modify ESPVR in the conscious state.7 A secondary goal was to determine whether or not the slopes and intercepts of these relations were different with these different types of loading modifications. Methods Surgical PreparationTen male beagle dogs weighing 9.6-15.0 kg (average, 12.4+0.4 kg) were used for this study.

The End-Systolic Pressure-Volume Relationship in the Newborn Lamb: Effects of Loading and Inotropic Interventions

“…From the linear ESPVR, two descriptors were calculated; the slope, or E e " and the V14. VI4 was used rather than Vd because the ESPVR has been demonstrated to be nonlinear to some extent in many preparations (24)(25)(26)(27)(28). Thus, extrapolation beyond the range of measurement is undesirable.…”

“…PV loops have been analyzed by a variety of techniques (13,14,35,(44)(45)(46), but most commonly by generating ESPVR, to assess ventricular function in control conditions and in response to various hemodynamic perturbations. There have, however, been several concerns about the ESPVR, including those of nonlinearity both outside and within the range of measurement (24)(25)(26)(27)(28), load dependency, particularly related to the technique of generating the relationship itself (13,IS,23,29), and relative insensitivity to changes in contractility (43). We have recently performed studies validating the accuracy of the conductance catheter in the in situ newborn heart (37), and undertook the present study to critically analyze the ESPVR in the newborn.…”

“…In the adult, the ESPVR has been shown to be relatively sensitive to changes in inotropic state (15,17,19,23), but evidence of nonlinearity (24)(25)(26)(27)(28) and afterload sensitivity (13,23,29,30) has been found. It is uncertain whether such problems would be more or less important in the newborn.…”

“…Pressure deficits during ejection probably do occur to some extent, caused by shortening deactivation and the internal resistance of series elastic elements. Recent studies in the adult dog have shown nonlinearity in a variety of settings, including high contractile states (25,26), over a wide range of preload (27,28) and during balloon aortic occlusion (24). The nonlinearity was considered significant only in those studies performed over a high range in preload (27,28), in which stroke volume changes greatly and thus quite variable pressure deficits can occur during the generation of the ESPVR.…”

Preload-Adjusted 2 Wave-Intensity Peaks Reflect Simultaneous Assessment of Left Ventricular Contractility and Relaxation

“…The goal of the present study was to determine whether the use of WI for the analysis of the pressure-volume relationship should be corrected for changes in preload. Theoretically, the end-systolic pressure-volume relationship by itself is an index of load dependent and of nonlinear characteristic, 12 but is also relatively load independent in the physiological range of animals and humans. [13][14][15][16] Therefore, the end-systolic pressure-volume relationship was used as a gold standard of the LV contractility.…”