title: Characterization and normal measurements of the left ventricular outflow tract by ECG-gated cardiac CT: implications for disorders of the outflow tract and aortic valve.
abstract: OBJECTIVE
  Studies suggest that electrocardiographically gated coronary computed tomographic angiography provides a clear definition of the left ventricular outflow tract (LVOT), and normal LVOT morphology may not be round, as assumed when the continuity equation is applied during echocardiography. The aims of this study were to demonstrate the morphology of the LVOT on coronary computed tomographic angiography and to establish normal values for LVOT measurements.
  
  
  METHODS
  Two independent readers retrospectively measured anterior-posterior (AP) and transverse diameters of the LVOT and performed LVOT planimetry on coronary computed tomographic angiographic studies of 106 consecutive patients with normal aortic valves.
  
  
  RESULTS
  Excellent interobserver agreement was observed for all measurements (r = 0.78-0.94). The LVOT was ovoid, with a larger transverse diameter than AP diameter during diastole and systole (P < .001). However, the ratio of AP diameter to transverse diameter was closer to 1.0 during systole (P < .001). Mean indexed LVOT area was minimally larger in systole than in diastole (P = .01-.04) and was larger in men than in women during diastole (P ≤ .001) and systole (P ≤ .01). Mean LVOT area indexed to body surface area was 2.3 ± 0.5 cm(2)/m(2) in women and 2.6 ± 0.7 cm(2)/m(2) in men. LVOT area demonstrated significant correlation with aortic root diameter.
  
  
  CONCLUSIONS
  The normal LVOT is ovoid in shape. LVOT is more circular during systole, but the AP diameter remains smaller than the transverse diameter throughout the cardiac cycle. The oval shape of the LVOT has important implications when LVOT area is calculated from LVOT diameters. Normal LVOT area values established in this study should facilitate diagnosis of the fixed component of LVOT obstruction.
authors.affiliation: Department of Radiology, Thomas Jefferson University Hospital, Main Building, 7th Floor, 132 S 10th Street, Philadelphia, PA 19107, USA. ethan.halpern@jefferson.edu
authors.forename: Ethan J
authors.initials: EJ
authors.lastname: Halpern
authors.forename: Shiva
authors.initials: S
authors.lastname: Gupta
authors.forename: David J
authors.initials: DJ
authors.lastname: Halpern
authors.forename: David H
authors.initials: DH
authors.lastname: Wiener
authors.forename: Alyson N
authors.initials: AN
authors.lastname: Owen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001021:Aortic Valve / Q000000981:diagnostic imaging*; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods*; D005260:Female; D006349:Heart Valve Diseases / Q000000981:diagnostic imaging*; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000379:methods; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014694:Ventricular Outflow Obstruction / Q000000981:diagnostic imaging*; D055815:Young Adult