Real world application of left ventricular outflow tract diameter prediction and clinical implications

Abstract

Abstract Background The Left Ventricular Outflow Tract diameter (LVOTd) measured with transthoracic echocardiogram is crucial for stroke volume, flow and effective orifice area (EOA) assessment in aortic stenosis (AS), but it’s also a source of error. A formula for its prediction has been proposed (Leye’s formula), based on body surface area (BSA). However, it has never been validated externally. Purpose The aim of study is to externally validate the equation by Leye et al. in a retrospective, single-center, large cohort of consecutive non-obese patients with severe symptomatic AS undergoing surgical aortic valve replacement. Methods A population of patients with severe symptomatic AS undergoing surgical aortic valve replacement was analyzed; three different LVOTd values were obtained for each patient: measured-LVOTd (m-LVOTd, from echo database), predicted-LVOTd (p-LVOTd, using Leye’s formula) and surgical-LVOTd (s-LVOTd, obtained by surgical reports). p-LVOTd was used to reevaluate stroke volume and EOA. Results Data from 735 patients were collected; mean age was 75±8 years and 417 patients (57%) were men, mean BMI was 25.6 kg/m2 and mean BSA was 1.8 m2. m-LVOTd was significantly lower than p-LVOTd (20.2±2.4mm and 22.4±1.0mm, respectively; bias 2.1mm; p < 0,001). Moreover the difference between p-LVOTd and s-LVOTd (23.2±1.7mm; bias 0.8 mm) was lower than the difference between m-LVOTd and s-LVOTd (bias 3.0 mm). When the stroke volume index (SVi) was calculated through p-LVOTd, its value increased significantly compared to SVi calculated with m-LVOTd (50.0±10.9 vs 40.9±10.2 mL/m2, p<0.001), leading to a significant decrease in patients classified as low-flow AS, from 216 (29%) to 73 (10%) (p<0.001). EOA calculated with p-LVOTd was significantly wider than that calculated using m-LVOTd, and correlation was weak (0.86±0.22 vs 0.70±0.16 cm2, p<0.001; r=0.599, p<0.001). Using the p-LVOTd instead of m-LVOTd has lead to the reclassification of 188 (26%) patients from EOA≤1 cm2 to EOA>1cm2. Conclusion We found that in non-obese patients with severe AS, LVOTd obtained from the simple formula proposed by Leye et al correlates better with the surgical annulus diameter compared with the echocardiographic measurement of LVOT, and this has relevant consequences on AS assessment.