Demonstration of left ventricular outflow tract eccentricity by real time 3D echocardiography: implications for the determination of aortic valve area.
BACKGROUND
Determination of the left ventricular outflow tract cross-sectional area (ALVOT) is necessary for calculating aortic valve area (AVA) by echocardiography using the continuity equation (CE). In the commonly applied form of CE, pir(2) is used to estimate ALVOT utilizing the assumptions that LVOT is round and the parasternal long axis (PLAX) plane bisects LVOT. Imaging LVOT using real time 3D echocardiography (RT3DE) eliminates the need for these assumptions. We tested the hypothesis that LVOT is round based on a formula for eccentricity.


RESULTS
In 53 patients, 2D echocardiography (2DE) and RT3DE were acquired. ALVOT was calculated by 2DE using pir(2) (ALVOT-2D). Using RT3DE, ALVOT planimetry was performed immediately beneath the aortic valve (ALVOT-3Dplan). Eccentricity Index (EI) was calculated using the shortest and longest LVOT diameters. The long axis was measured to be larger by 0.53 cm +/- 0.36 (P < 0.005). The median EI was 0.20 (0.00-0.54), indicating that half the subjects had at least a 20% difference between the major and minor diameters. ALVOT-3Dplan was larger than ALVOT-2D (3.73 +/- 0.95 cm(2) vs. 3.18 +/- 0.73 cm(2); P < 0.001) by paired analysis. Using the equation of an ellipse (piab), ALVOT-3Dellip was 3.57 +/- 0.95 resulting in improved agreement with ALVOT-3Dplan.


CONCLUSIONS
In our small patient sample with normal aortic valves, we showed the LVOT shape is usually not round and frequently, elliptical. Incorrectly assuming a round LVOT underestimated the ALVOT-3Dplan and consequently the AVA by 15%. Investigating the LVOT in aortic stenosis is warranted to evaluate whether RT3DE may improve measurement of AVA.
Doddamani
Sanjay
S
Department of Medicine, Division of Cardiology, Montefiore Medical Center, Albert Einstein College of Medicine, 111 East 210th Street, Bronx, NY 10461, USA. doddamas@montefiore.org
Bello
Ricardo
R
Friedman
Mark A
MA
Banerjee
Anita
A
Bowers
James H
JH
Kim
Bette
B
Vennalaganti
Prashant R
PR
Ostfeld
Robert J
RJ
Gordon
Garet M
GM
Malhotra
Divya
D
Spevack
Daniel M
DM
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001021:Aortic Valve / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D019560:Echocardiography, Three-Dimensional; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D016277:Ventricular Function, Left