title: Impact of left ventricular outflow tract area on systolic outflow velocity in hypertrophic cardiomyopathy: a real-time three-dimensional echocardiographic study.
abstract: OBJECTIVE
  The aim of this study was to use real-time three-dimensional echocardiography (3DE) to investigate the quantitative relation between minimal left ventricular (LV) outflow tract area (A(LVOT)) and maximal LV outflow tract (LVOT) velocity in patients with hypertrophic obstructive cardiomyopathy (HCM).
  
  
  BACKGROUND
  In patients with HCM, LVOT velocity should change inversely with minimal A(LVOT) unless LVOT obstruction reduces the pumping capacity of the ventricle.
  
  
  METHODS
  A total of 25 patients with HCM with systolic anterior motion (SAM) of the mitral valve leaflets underwent real-time 3DE. The smallest A(LVOT) during systole was measured using anatomically oriented two-dimensional "C-planes" within the pyramidal 3DE volume. Maximal velocity across LVOT was evaluated by two-dimensional Doppler echocardiography (2DE). For comparison with 3DE A(LVOT), the SAM-septal distance was determined by 2DE.
  
  
  RESULTS
  Real-time 3DE provided unique information about the dynamic SAM-septal relation during systole, with A(LVOT) ranging from 0.6 to 5.2 cm(2) (mean: 2.2 +/- 1.4 cm(2)). Maximal velocity (v) correlated inversely with A(LVOT) (v = 496 A(LVOT)(-0.80), r = -0.95, p < 0.001), but the exponent (-0.80) was significantly different from -1.0 (95% confidence interval: -0.67 to -0.92), indicating a significant impact of small A(LVOT) on the peak LVOT flow rate. By comparison, the best correlation between velocity and 2DE SAM-septal distance was significantly (p < 0.01) poorer at -0.83, indicating the superiority of 3DE for assessing A(LVOT).
  
  
  CONCLUSIONS
  Three-dimensional echocardiography-measured A(LVOT) provides an assessment of HCM geometry that is superior to 2DE methods. These data indicate that the peak LVOT flow rate appears to be significantly decreased by reduced A(LVOT). Real-time 3DE is a potentially valuable clinical tool for assessing patients with HCM.
authors.affiliation: Department of Cardiology, the Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Jian Xin
authors.initials: JX
authors.lastname: Qin
authors.forename: Takahiro
authors.initials: T
authors.lastname: Shiota
authors.forename: Harry M
authors.initials: HM
authors.lastname: Lever
authors.forename: David N
authors.initials: DN
authors.lastname: Rubin
authors.forename: Fabrice
authors.initials: F
authors.lastname: Bauer
authors.forename: Yong Jin
authors.initials: YJ
authors.lastname: Kim
authors.forename: Marta
authors.initials: M
authors.lastname: Sitges
authors.forename: Neil L
authors.initials: NL
authors.lastname: Greenberg
authors.forename: Jeanne K
authors.initials: JK
authors.lastname: Drinko
authors.forename: Maureen
authors.initials: M
authors.lastname: Martin
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Agler
authors.forename: James D
authors.initials: JD
authors.lastname: Thomas
mesh_terms: D000328:Adult; D000368:Aged; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003326:Coronary Circulation; D019560:Echocardiography, Three-Dimensional; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008944:Mitral Valve Insufficiency / Q000150:complications; D014694:Ventricular Outflow Obstruction / Q000150:complications / Q000503:physiopathology*