Influence of BSA-based LVOT diameter estimation on grading of aortic stenosis

Introduction The continuity equation is widely used to calculate the aortic valve area (AVA), which is essential for evaluating the severity of aortic stenosis (AS). A key component of this method is accurately measuring the left ventricular outflow tract (LVOT) area. Variations in how the LVOT area is determined can significantly affect the final AVA measurement, potentially leading to misclassification of AS severity. Traditional methods rely on direct imaging and measurement, which can be subject to operator variability. In order to provide a more standardized approach, formulas have been developed to estimate the LVOT diameter (LVOTd) based on body surface area (BSA). The impact of using these formulas on the reclassification of AS severity in patient populations remains understudied. Aim Assess how different methods of estimating the LVOT area impact AS grading Methods Retrospective study. Consecutive patients with diagnosis of moderate/severe AS between January 2020 and April 2025 were included. Predicted LVOTd by BSA was calculated by the formula: (5.7*BSA + 12). To compare the classification of AS between the two methods, McNemar test was used. Results A total of 1,273 patients were included, with 56% being male, with a mean age of 77 ± 9 years. Echocardiographic data showed a mean maximum jet velocity (MaxVel) of 4.0 ± 0.7 m/s, a mean transaortic pressure gradient (MG) of 39 ± 15 mmHg, a mean aortic valve area (AVA) of 0.89 ± 0.26 cm², an indexed AVA (iAVA) of 0.50 ± 0.14 cm²/m², and a velocity time integral ratio (DVI) of 0.25 ± 0.07. Table 1 presents the incidence of moderate and severe AS, along with AVA and iAVA values. AVA and iAVA calculated from the predicted LVOT diameter based on BSA tended to be slightly higher. Notably, AVA derived from the LVOT diameter predicted by BSA was associated with a lower prevalence of severe high-gradient (HG) AS and a lower prevalence of low-flow, low-gradient (LFLG) AS. Using AVA predicted by BSA values led to reclassification from severe (according to the standard method) to non-severe in a significant proportion of patients (9.3%; McNemar test p < 0.001). A subanalysis of 1,112 patients with BSA £ 2 m² showed similar findings, with a reclassification from severe to non-severe in 8.1% of patients (McNemar test p < 0.001). Regarding gender (population characteristics are summarized in Table 2), similar reclassification patterns were observed in both groups, with a significant proportion shifting from severe to non-severe AS — 5.4% in males and 12.9% in females (both p < 0.001 in McNemar test). Conclusion Our study suggests that, despite efforts to minimize errors associated with LVOT diameter measurement, estimating the LVOT diameter using BSA-based formulas leads to significant reclassification of aortic stenosis severity. These results underscore the impact of LVOT measurement methodology on AS grading and suggest that formula-based estimations may influence clinical decision-making.