Implications of methods for calculating the left ventricular outflow tract area in aortic stenosis severity grading

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): - Spanish Ministry of Economy and Competitiveness through the Carlos III Institute of Health-Fondo de Investigación Sanitaria. - Post-residency research contract. Medical Research Institute Hospital La Fe (IIS La Fe), Valencia, Spain. Introduction Aortic valve area (AVA) calculation by continuity equation is a fundamental aspect to estimate aortic stenosis (AS) severity. The estimation of the left ventricular outflow tract (LVOT) area is a source of technical variability in the calculation of AVA that can lead to errors in severity grading. Formulas for calculating LVOT diameter (LVOTd) based on body surface area (BSA) and patient height have been proposed, but their impact on reclassifying patients based on severity has not been described. Purpose To evaluate the differences in AS grading according to the LVOT area used in the calculation of the AVA. Methods We retrospectively analyzed (2019–2022) 1722 echocardiograms with a diagnosis of AS and with the following variables reported: AVA calculated using the continuity equation, height and weight of the patient. Predicted LVOTd by BSA was calculated by the formula: (5.7*BSA + 12). Predicted LVOTd by height was calculated as: (5.78 * height + 12.1). Results LVOT area and AVA from predicted LVOTd based on BSA and height showed slightly higher values. The AVA based on the LVOTd predicted by BSA was associated with a lower prevalence of severe AS, as well as a lower prevalence of discordant cases (mean gradient <40 mmHg and AVA <1 cm2) (Table). The AVA based on both methods of predicted LVOTd led to a reclassification from severe (by the standard method) to non-severe in a significant percentage of patients (13.6% for the BSA-predicted method, and 8.7% for the height-predicted method). For the AVA predicted by BSA, the "downgrade" of AS severity was more frequent (23.3%) in patients in the quartile with the highest BMI (>30 kg/m2), while the degree of obesity did not affect the method predicted by height. Conclusion Despite suppressing the potential errors derived from the LVOTd measurement, the AVA based on predicted LVOTd methods using BSA or height lead to a significant percentage of reclassification in terms of severity and prevalence of discordant severe AS due to low gradient. In obese patients, the method predicted by BSA is highly discordant and the method predicted by the patient's height is preferable.