title: Application of a time varying elastance model to right ventricular performance in man.
abstract: To evaluate instantaneous right ventricular pressure-volume relations we studied nine patients with normal coronary anatomy and ventricular function with simultaneous high fidelity pressure, flow-velocity, and biplane cineventriculographic volumes (60 frames.s-1) during atrial pacing at 93(SD5) beats-min-1, partial autonomic blockade, and pharmacologically altered ventricular loading. The maximum time varying elastance, Emax, was defined as the maximum slope of isochronal, simultaneous pressure-volume data points derived by linear regression analysis from three loading conditions. The slope of the non-isochronal maximum pressure/volume ratio, pressure at minimum volume, end ejection pressure/volume, and peak right ventricular pressure/minimum volume were also derived from the three loading conditions. The mean slope for Emax was 1.30(0.84) mm Hg.ml-1 (range 0.62-2.87) and the volume axis intercept at zero pressure (Vo) was 46(21) ml (range 24-89 ml). Time dependent Emax was characterised by a series of parallel shifting lines of best fit with large changes in Vo in addition to changes in the slope of the pressure volume relations. Only maximum pressure/volume ratio and peak pressure/minimum volume were linearly related to Emax (r = 0.82 and 0.84 respectively, p = 0.05) while pressure at minimum volume and end ejection pressure/volume did not correlate with Emax. We conclude that in normal human subjects (1) right ventricular systolic function may be approximated using a time varying elastance model characterised by a time dependent Vo; (2) end systolic pressure-volume relations using maximum pressure/volume ratio and peak pressure/minimum volume systematically estimate Emax; and (3) other right ventricular end systolic pressure-volume relations near end ejection bear no obvious relation to Emax because of the wide temporal separation between peak systolic elastance and end ejection in this chamber.
authors.affiliation: Department of Medicine, University of Texas Health Science Center, San Antonio 78284-7872.
authors.forename: L J
authors.initials: LJ
authors.lastname: Dell'Italia
authors.forename: R A
authors.initials: RA
authors.lastname: Walsh
mesh_terms: D000328:Adult; D004548:Elasticity; D005260:Female; D006321:Heart / Q000502:physiology*; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D011312:Pressure; D016276:Ventricular Function