Impact of Three-Dimensional Echocardiography on Classification of the Severity of Aortic Stenosis

Background Owing to its elliptical shape, the left ventricle outflow tract (LVOT) area is underestimated by two-dimensional (2D) diameter-based calculations which assume a circular shape. This results in overestimation of aortic stenosis (AS) by the continuity equation. In cases of moderate to severe AS, this overestimation can affect intraoperative clinical decision making (expectant management versus replacement). The purpose of this intraoperative study was to compare the aortic valve area calculated by 2D diameter based and three-dimensional (3D) derived LVOT area via transesophageal echocardiography (TEE) and its impact on severity of AS. Methods The LVOT area was calculated using intraoperative 2D and 3D TEE data from patients undergoing aortic valve replacement (AVR) and coronary artery bypass graft (CABG) surgery using the 2D diameter (RADIUS), 3D planimetry (PLANE), and 3D biplane (π·x·y) measurement (ELLIPSE) methods. For each method, the LVOT area was used to determine the aortic valve area by the continuity equation and the severity of AS categorized as mild, moderate, or severe. Results A total of 66 patients completed the study. The RADIUS method (3.5 ± 0.9 cm2 ) underestimated LVOT area by 21% ( p < 0.05) compared with the PLANE method (4.1 ± 0.1 cm2 ) and by 18% ( p < 0.05) compared with the ELLIPSE method (4.0 ± 0.9 cm2 ). There was no significant difference between the two 3D methods, namely, PLANE and ELLIPSE. Seven AVR patients (18%) and 1 CABG surgery patient (6%) who had originally been classified as severe AS by the 2D method were reclassified as moderate AS by the 3D methods ( p < 0.001). Conclusions Three-dimensional echocardiography has the potential to impact surgical decision making in cases of moderate to severe AS.