Echocardiographic evaluation of severe aortic stenosis: impact of three-dimensional imaging and correction for pressure recovery

Abstract

Purpose: In patients with Aortic Stenosis (AS), echocardiographic grading of stenosis severity is important, in particular when valve surgery or Transcatheter Aortic Valve Implantation (TAVI) are considered. Energy Loss Index (ELI) has been proposed to improve the determination of aortic valve area (AVA) by correcting for the effects of pressure recovery. However, the impact of ELI on calculation of AVA in patients with severe AS has not been studied, and the effect of 3D echocardiography in this context is not known. Methods: Transthoracic (TTE) and Transesophageal (TEE) echocardiography studies of 40 patients (54% males) with severe AS evaluated for TAVI were analyzed. AVA was calculated by the continuity equation based on Left Ventricular Outflow Tract (LVOT) diameter measured in 2D-TTE and 2D-TEE as well as based on LVOT area measured in 3D-TEE. In addition, AVA determined by 3D-TEE measurements was corrected for ELI (ELI = [(AVA × Aortic area)/Aortic area – AVA)]/body surface area). AVA and indexed AVA (AVAI) obtained from these four methods were compared. Results: LVOT area was 2.45±0.91 cm2 calculated using 2D-TTE diameter measurements, 2.82±0.78 cm2 calculated using 2D-TEE diameter measurements, and 4.27±0.89 cm2 measured in 3D-TEE (p 0.85 cm2/m2. Conclusions: Since the true LVOT is not circular, the geometric assumptions used for calculation of AVAI from 2D measurements lead to underestimation of AVA in patients with severe AS. The effects of pressure recovery accentuate this problem. When both the true LVOT area and the effects of pressure recovery are considered, AS needs to be reclassified from severe to moderate in over a third of patients. The implementation of these parameters in echocardiographic practice might improve the accuracy of AS severity assessment.