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A4036
October 14, 2014
10:00 AM - 11:30 AM
Room Room 243
Regional Variability in Left Ventricular Outflow Tract Shape: A Three-Dimensional Transesophageal Echocardiography Study
Anam Pal, M.D., Mario Montealegre-Gallegos, M.D., Jacob A. Clark, M.D., Khurram Owais, M.D., Robina Matyal, M.D., Thomas Huang, B.A., Jeffrey B. Hubbard, M.D., Vwaire Orhurhu, B.A., M.P.H., Feroze Mahmood, M.D.
Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
Introduction

The cross-sectional area of the left ventricular outflow tract (LVOT) is integral in the calculation of aortic valve area and stroke volume with continuity equation-derived methods. The most common method of estimating the LVOT area is by measuring its diameter in the mid-esophageal long axis view (πr2). This method of estimation assumes that the LVOT possesses a circular shape. Recent evidence suggests the LVOT is elliptical rather than circular.

Our main objective was to determine if the ellipticity of the LVOT is uniform along its long axis or if it differs by the sampled region.

Methods

26 consecutive patients undergoing isolated coronary artery bypass graft surgery with intraoperative 3-dimensional (3D) transesophageal echocardiography (TEE) were studied. 3D R-wave gated images of the LVOT were analyzed with QLAB quantification software. Multi-planar reformatting planes were aligned orthogonally to display an en face view of the LVOT during mid-systole in 3 different regions: (1) immediately adjacent to the aortic annulus or distal, (2) 1 cm proximal to the aortic annulus or mid, and (3) at the starting point of the LVOT or proximal. For each region the major (x) and minor (y) axes on the enface views were measured (Figure 1), and the area planimetered as well. Data were analyzed with repeated measures analysis of variance and are presented as mean ± standard deviation.

Results

26 patients completed the study. Mean age was 67.8± 10.7 years, and 73% were males.

The LVOT major axis diameter decreased significantly (p=0.000) from the proximal to distal positions, whereas minor axis diameter did not decrease in relation to the region studied (p=0.441). Area by planimetry decreased progressively from proximal to distal (p=0.000), (table 1).

Discussion

Variation in ellipticity along the LVOT may affect the reliability of estimating its cross-sectional area with 2D TEE. This may be more pronounced in more proximal regions of the LVOT, where the ellipticity is highest.

LVOT area obtained by planimetry is also highly variable, with more proximal regions having a larger area.

Conclusion

Heterogenicity of LVOT shape may make 2D TEE unreliable in estimating LVOT area, particularly when the measurement is made proximally. The regional variation in LVOT area may result in inaccuracy in the estimation of aortic valve areas or stroke volume by continuity equation derived methods.

Figure legend

Figure 1: Orthogonal alignment of multiplanar reformatting planes (A, B, C, D). (A)- Red plane across the middle portion of the LVOT; (B) en face view of the LVOT with minor (D1) and major (D2) axes and planimetry (A1)

Figure 1
Figure 2

Copyright © 2014 American Society of Anesthesiologists