Comprehensive Echocardiographic Assessment in Moderate Aortic Stenosis with Preserved Ejection Fraction Using Two-Dimensional Speckle-Tracking Echocardiography: Association with Functional Capacity

<b>Background/Objectives</b>: Moderate aortic stenosis (AS) with preserved ejection fraction (EF) is common, yet risk stratification remains challenging. Cardiopulmonary exercise testing (CPET) and myocardial mechanics analysis may identify subclinical dysfunction and impaired functional capacity. To evaluate the relationship between functional capacity (by % predicted peak VO₂), ventilatory efficiency (VE/VCO₂ slope), and myocardial mechanics (speckle tracking echocardiography-STE), and myocardial work (MW) indices) in moderate AS with preserved EF. <b>Methods</b>: We prospectively enrolled 107 patients with moderate AS (AVA 1.0-1.5 cm²; mean gradient 20-40 mmHg; EF ≥ 50%). Functional capacity was classified as preserved (≥83% predicted VO₂) or reduced (<83%). Ventilatory efficiency was defined as good (<30) or poor (≥30) VE/VCO₂ slope. STE assessed left ventricular (LV), left atrial (LA), and right ventricular (RV) strain, as well as myocardial work indices. <b>Results</b>: Patients with reduced % predicted VO₂ had higher LV end-systolic volume (<i>p</i> = 0.035), lower stroke volume index (<i>p</i> = 0.020), and smaller indexed aortic valve area (<i>p</i> = 0.025), with trends toward lower GLS and myocardial work. In contrast, patients with poor ventilatory efficiency (VE/VCO₂ ≥ 30) showed significant impairments in global longitudinal strain (GLS, <i>p</i> = 0.002), LA reservoir strain (PALS, <i>p</i> = 0.019) and LA conduit strain (LA Scd, <i>p</i> < 0.001), RV free wall strain (RW FWS, <i>p</i> = 0.029), and myocardial work indices (lower GWI and GCW, higher GWW, reduced GWE; all <i>p</i> < 0.05). LA Scd emerged as the strongest predictor of poor ventilatory efficiency. (receiver operating characteristic (ROC) area under the curve (AUC) 0.723, 95% confidence interval (CI) 0.623-0.823, <i>p</i> < 0.001). <b>Conclusions</b>: In moderate AS with preserved EF, impaired ventilatory efficiency is more strongly associated with subclinical LV, LA, and RV dysfunction than reduced % predicted VO₂, highlighting the key role of RV impairment. Integrating CPET and STE improves phenotyping, identifying high-risk patients who may benefit from closer surveillance or early intervention. These findings are exploratory and hypothesis-generating; longitudinal data are needed to confirm prognostic implications.