3D-Transesophageal Echocardiography in Paradoxical Low-Flow, Low- Gradient Aortic Stenosis

pp. 326-332

Abstract

Background: In paradoxical low-flow, low gradient (LF-LG) aortic stenosis, 2D-transthoracic echocardiography (2D-TTE) may underestimate flow because it assumes a circular left ventricular outflow tract (LVOT) shape. Three-dimensional transesophageal echocardiography (3D-TEE) is a better method to measure LVOT area.

Objectives: The aim of this study was to evaluate left ventricular stroke volume index (SVi) by 2D-TTE and 3D-TEE in patients with normal heart (NG) and with severe aortic stenosis (ASG) and to determine how many patients are categorized as paradoxical LF-LG by 2D-TTE and 3D-TEE.

Methods: Thirty-five patients were evaluated by 2D-TEE and 3D-TEE: NG=17 patients and ASG=18 patients. Left ventricular outflow tract area was estimated during early systole (ES) by 2D-TTE (ES2DLVOT Ar) and by 3D-TEE (ES3DLVOT Ar) planimetry, and as systolic average (Avg 3DLVOT Ar). Each LVOT area was multiplied by its corresponding flow integral to obtain SVi (ES2D- TTE SVi, ES3D-TEE SVi and Avg 3D-TEE SVi) in NG and ASG. Paradoxical LF-LG was determined in ASG following standard criterion.

Results: NG: ES2DLVOT Ar vs. ES3DLVOT Ar p<0.05; ASG: ES2DLVOT Ar vs. ES3DLVOT Ar p<0.001 and vs. Avg 3DLVOT Ar p<0.023; ES2D-TTE SVi vs. ES3D-TEE SVi p<0.002 and vs. Avg 3D-TEE SVi p<0.038. In the NG, the lower limit of normal SVi for 2D-TTE, ES3D-TEE and Avg 3D-TEE was <34, <38.9 and <35.9 ml/m2, respectively. Three patients with severe aortic stenosis were categorized as paradoxical LF-LG by 2D-TTE, but none by 3D-TEE.

Conclusions: Patients with paradoxical LF-LG by 2D-TTE could be recategorized by 3D-TEE. This finding is related with the limitations of 2D-echocardiography for estimating LVOT area.