title: Time-varying elastance concept applied to the relation of carotid arterial flow velocity and ventricular area.
abstract: OBJECTIVE
  In this study, the relationship V(f)AR, which was obtained from carotid blood-flow velocity (V(f)) and the cross-sectional area (A) of the left ventricle, was used to assess changes in left ventricular (LV) systolic performance as indicated by the LV pressure-volume relationship (PVR) and end-systolic LV elastance (E(es)).
  
  
  BACKGROUND
  The relationship of maximum systolic V(f) as a surrogate for LV pressure and end-systolic LV area as a surrogate for end-systolic LV volume may allow for the estimation of LV elastance and ejection properties.
  
  
  METHODS
  In 25 pigs, internal carotid V(f) was recorded by using continuous-wave Doppler mode. Echocardiographic measurements of A were continuously performed with an automated border detection system and combined with data for V(f) to display V(f)AR as a series of loop diagrams. These were shifted during acute preload reduction, and an index E'(es) was calculated by applying the time varying elastance concept to end-systolic V(f)AR. Simultaneously, E(es) was acquired by conductance catheter and micromanometer techniques. Comparisons of E'(es) and E(es) were made at various contractility levels obtained by the administration of dobutamine, 5 microg/kg/min, and esmolol, 40 to 60 mg, and at various cardiac load levels, obtained by a fluid bolus infusion or administration of a vasoconstrictor.
  
  
  RESULTS
  Highly linear elastance curves (r >or= 0.85, p < 0.0001) were derived from both end-systolic V(f)AR and PVR. Correlation of E'(es) and E(es) revealed an almost linear function: E'(es) = 0.052 + 0.11 E(es) (r = 0.98, p < 0.0001). Administration of dobutamine increased E(es) from 5.8 +/- 3.04 mmHg/mL to 10.1 +/- 4.19 mmHg/mL (p < 0.05), and E('es) from 0.68 +/- 0.288 cm(2)/min/mL to 1.24 +/- 0.458 cm(2)/min/mL (p < 0.05). After administration of esmolol, E(es) and E'(es) both dropped significantly by 3.7 +/- 2.4 mmHg/mL and 0.44 +/- 0.15 cm(2)/min/mL, respectively. No load dependency of E'(es) was seen. Bland-Altman analysis revealed that the change in E'(es), which is required to predict a significant change in E(es), should exceed +16.9% or -13.1% of the preceding value.
  
  
  CONCLUSIONS
  Application of the time-varying elastance concept on the relation of V(f) and LV area allows for the determination of an index E'(es) that may be used to estimate E(es).
authors.affiliation: Department of Anesthesiology, University of Wuerzburg, Wuerzburg, Germany. broscheit_j@kinik.uni-wuerzburg.de
authors.forename: Jens-Albert
authors.initials: JA
authors.lastname: Broscheit
authors.forename: Frank
authors.initials: F
authors.lastname: Weidemann
authors.forename: Jörg
authors.initials: J
authors.lastname: Strotmann
authors.forename: Paul
authors.initials: P
authors.lastname: Steendijk
authors.forename: Holger
authors.initials: H
authors.lastname: Karle
authors.forename: Norbert
authors.initials: N
authors.lastname: Roewer
authors.forename: Clemens-Alexander
authors.initials: CA
authors.lastname: Greim
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity; D002339:Carotid Arteries / Q000502:physiology*; D004562:Electrocardiography; D017078:Laser-Doppler Flowmetry; D009200:Myocardial Contraction; D013552:Swine; D013556:Swine, Miniature; D016277:Ventricular Function, Left