Acceleration time as a predictor of true severity in low-flow low-gradient aortic stenosis: insights from dobutamine stress echocardiography
F Rodrigues Santos, O Kungel, G Ferreira, J Gouveia Fiuza, M Duarte Almeida, L Afonso Santos, A Costa, I Fiuza PiresAbstract
Introduction
Low-flow low-gradient aortic stenosis (LFLG-AS) represents a diagnostic challenge, as resting echocardiographic parameters often fail to accurately discriminate between truly severe and pseudo-severe stenosis. Dobutamine stress echocardiography (DSE) remains the reference method for severity assessment. Acceleration time (AT), reflecting transvalvular flow dynamics, has emerged as a potential marker of valvular obstruction. This study aimed to evaluate the impact of resting AT on the prediction of true severe AS in patients with LFLG-AS undergoing DSE.
Methods
We conducted a retrospective single-centre study including patients with LFLG-AS who underwent DSE between January 2020 and December 2024. Inclusion criteria were: aortic valve area (AVA) ≤1.0 cm², mean transvalvular gradient <40 mmHg, stroke volume index <35 mL/m², and LVEF ≤50%. Resting transthoracic echocardiography was used to measure AT at the left ventricular outflow tract using pulsed-wave Doppler. True severe AS was defined during DSE as an AVA ≤1.0 cm² with a mean gradient ≥40 mmHg or projected AVA ≤1.0 cm² under increased flow. Clinical, echocardiographic and hemodynamic variables were analyzed. Multivariate logistic regression and receiver operating characteristic (ROC) curve analyses were performed to assess the predictive value of AT.
Results
A total of 75 patients were included, of whom 69.3% (n=52) were male, with a mean age of 72.8 ± 8.9 years. Mean baseline LVEF was 38.6 ± 7.8%, mean AVA 0.82 ± 0.12 cm², and mean transvalvular gradient 28.4 ± 6.1 mmHg. During DSE, 46 patients (61.3%) were classified as having true severe AS, while 29 (38.7%) were reclassified as pseudo-severe/moderate AS. Resting AT was significantly longer in patients with true severe AS compared to those with pseudo-severe AS (146 ± 18 ms vs. 125 ± 16 ms, p=0.02). An AT ≥140 ms was present in 73.9% of patients with true severe AS versus 37.2% in the pseudo-severe group (χ² = 12.6, p = 0.016). In multivariate logistic regression analysis adjusting for age, sex, LVEF, stroke volume index, and valvulo-arterial impedance, AT remained an independent predictor of true severe AS (OR 2.42, 95% CI 1.41–11.12, p= 0.002). ROC curve analysis demonstrated good discriminative ability of AT for predicting true severe AS (AUC 0.80), outperforming resting mean gradient (AUC 0.67) and AVA alone (AUC 0.70).
Conclusion
In patients with low-flow low-gradient aortic stenosis, resting acceleration time is a strong and independent predictor of true severe disease as confirmed by dobutamine stress echocardiography. An AT ≥140 ms identifies patients more likely to harbor truly severe AS, even before stress testing. These findings support the incorporation of AT into the routine echocardiographic assessment of LFLG-AS, potentially improving risk stratification and optimizing patient selection for advanced diagnostic and therapeutic strategies.