title: Effect of load alterations on the effective regurgitant orifice area in chronic aortic regurgitation.
abstract: OBJECTIVE
  To evaluate the load dependence of effective regurgitant orifice area (ROA) in an animal model of chronic aortic regurgitation.
  
  
  METHODS
  Eight sheep were studied 10-20 weeks after the surgical creation of aortic regurgitation. After baseline studies, 500 ml of blood, angiotensin II, and nitroprusside were infused sequentially. Electromagnetic flow meters were used as reference standards to determine aortic regurgitation volume. The time-velocity integral was acquired using the continuous wave Doppler method.
  
  
  RESULTS
  Baseline aortic regurgitant volume varied from 8 ml (regurgitant fraction 28%) to 29 ml (59%), with a mean (SD) value of 17 (8) ml; mean ROA was 0.15 (0.05) cm2. During angiotensin II infusion, aortic regurgitation volume (20 (8) ml) and mean diastolic aortoventricular pressure gradient (62 (18) mm Hg) increased by 26 (16)% and 48 (64)%, respectively (p < 0.01 for both). ROA did not change (0.16 (0.06) cm(2), p = 0.15). During nitroprusside infusion, aortic regurgitant volume (13 (7) ml, p = 0.05) and diastolic pressure gradient (25 (13) mm Hg, p < 0.05) decreased. ROA did not change (0.15 (0.05) cm2). When analysing 32 stages together, aortic regurgitant volume (r = 0.78, p < 0.01) and regurgitant fraction (r = 0.55, p < 0.01) correlated well with ROA. However, diastolic pressure gradient (r = 0.28) was not significantly correlated with ROA.
  
  
  CONCLUSIONS
  In an animal model of chronic aortic regurgitation, ROA did not change with load alterations.
authors.affiliation: The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Kim
authors.forename: M
authors.initials: M
authors.lastname: Jones
authors.forename: T
authors.initials: T
authors.lastname: Shiota
authors.forename: H
authors.initials: H
authors.lastname: Tsujino
authors.forename: J X
authors.initials: JX
authors.lastname: Qin
authors.forename: F
authors.initials: F
authors.lastname: Bauer
authors.forename: M
authors.initials: M
authors.lastname: Sitges
authors.forename: J
authors.initials: J
authors.lastname: Kwan
authors.forename: L A
authors.initials: LA
authors.lastname: Cardon
authors.forename: A D
authors.initials: AD
authors.lastname: Zetts
authors.forename: J D
authors.initials: JD
authors.lastname: Thomas
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001022:Aortic Valve Insufficiency / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001783:Blood Flow Velocity / Q000187:drug effects; D001803:Blood Transfusion; D002908:Chronic Disease; D015150:Echocardiography, Doppler / Q000379:methods; D006439:Hemodynamics; D009599:Nitroprusside / Q000494:pharmacology; D012044:Regression Analysis; D012756:Sheep; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D000804:Angiotensin II; D009599:Nitroprusside