Prognostic Implications of Discordant Low-Gradient Severe Aortic Stenosis: A Comprehensive Review of Pathophysiological Mechanisms, Diagnostic Challenges, and Clinical Outcomes

Discordant low-gradient severe aortic stenosis (DLG-SAS) represents a clinically complex and prognostically heterogeneous entity characterized by a discrepancy between aortic valve area (AVA) criteria for severe stenosis (AVA <1.0 cm²) and a non-classical transvalvular gradient (mean gradient <40 mmHg). This condition poses significant diagnostic and therapeutic dilemmas due to its multifactorial pathophysiology, which includes impaired left ventricular (LV) systolic function (classical low-flow, low-gradient SAS), preserved LV ejection fraction with paradoxical low-flow states, and measurement artifacts. Emerging evidence suggests that DLG-SAS carries distinct prognostic implications, with varying mortality risks depending on underlying hemodynamic profiles, comorbidities, and therapeutic interventions. This review synthesizes current literature on the pathophysiological substrates, advanced imaging modalities (e.g., dobutamine stress echocardiography, computed tomography-derived aortic valve calcification scoring), and risk stratification paradigms. Furthermore, we evaluate the impact of treatment strategies, including transcatheter aortic valve replacement (TAVR) versus surgical aortic valve replacement (SAVR), on long-term outcomes. By elucidating the interplay between hemodynamic parameters, myocardial remodeling, and clinical trajectories, this article aims to refine prognostic assessment and guide evidence-based management of DLG-SAS.