The Left Ventricular Outflow Tract Changes in Size and Shape From Pre- to Post-Cardiopulmonary Bypass: Three-Dimensional Transesophageal Echocardiography

Abstract

Objectives: To compare two-dimensional (2D) and 3D imaging of the left ventricular outflow tract (LVOT) and to evaluate geometric changes pre- to post-cardiopulmonary bypass (CPB).

Design: Retrospective review of intraoperative transesophageal echocardiographic examinations.

Setting: Single academic medical center.

Participants: The study comprised 69 cardiac surgical patients-27 with aortic valve stenosis (AS) and 42 without AS.

Interventions: Two-dimensional and 3D analysis of the LVOT pre- and post-CPB.

Measurements and main results: Pre- and post-CPB 2D assessment of LVOT diameter (2D LVOTd) was compared with 3D analysis of the minor (3D LVOTd-min) and major diameters. LVOT areas (LVOTa) were calculated using LVOTd to yield 2D LVOTa and 3D LVOTa-min. These were compared with LVOTa measured by planimetry (3D LVOTa-plan). An ellipticity ratio (ER) (ER = 3D minor/major axes) was calculated. The 2D LVOTd was larger than the 3D LVOTd-min before (2.12 v 2.02 cm respectively (resp); p < 0.001) and after (1.96 v 1.85 cm resp; p = 0.04) CPB. Compared with pre-CPB, there were significant decreases in the 2D LVOTd (p = 0.003) and the 3D LVOTd-min (p < 0.001) post-CPB. Ellipticity increased after CPB (ER 0.80 v 0.75; p = 0.004), and the 2D LVOTa was larger than the 3D LVOTa-min before CPB (3.60 cm²v 3.28 cm²; p < 0.001) and less so after CPB (3.11 cm²v 2.79 cm²; p = 0.053). Compared with pre-CPB, all LVOTa measurements decreased significantly after CPB (p < 0.001). The 3D LVOTa-plan decreased after CPB by approximately 10% (4.05 cm²v 3.61 cm²; p < 0.001). The 2D LVOTa and 3D LVOTa-min underestimated the 3D LVOTa-plan before and after CPB (p < 0.001) by 11% to 14% and 19% to 23%, respectively. When compared with non-AS patients, patients with AS had a smaller LVOTa pre- and post-CPB (p < 0.05).

Conclusions: The LVOT is smaller and more elliptical after CPB. Patients with AS have a smaller LVOT compared with non-AS patients. LVOTa calculated using LVOTd underestimates the 3D LVOTa-plan by as much as 23% depending on patient type and timing of measurement. Accurate assessment of the LVOT requires 3D imaging.

Keywords: cardiopulmonary bypass; left ventricular outflow tract; three-dimensional; two-dimensional.