Introducció: L'estenosi aòrtica (EAo) de baix flux i baix gradient (BF/BG) amb fracció d'ejecció del ventricle esquerre (FEVE) normal és una entitat que s'ha associat amb un pitjor pronòstic que l'EAo d'elevat gradient (EG); tot i això, diferents estudis i recents meta-anàlisis posen en dubte els resultats previs. Objectiu: Determinar el risc de mortalitat i/o necessitat de cirurgia/TAVI en els pacients amb EAo severa amb BF/BG i FEVE conservada en comparació amb l'EAo severa amb flux normal i baix gradient (NF/BG) i amb EG. Materials i mètodes: Estudi observacional longitudinal retrospectiu de pacients diagnosticats entre 2008 i 2016 d'EAo severa (AVA 35 ml/m² i gradient mig 35 ml/m² y gradiente medio 35 ml/m² and mean gradient <40 mmHg) and LF/LG (SVi ≤ 35 ml / m² and mean gradient <40 mmHg). Baseline and long-term clinical, demographic and echocardiographic variables were collected. Results: A total of 1,391 patients were included and classified as: 147 (10.5%) LF/LG, 752 (54 0.1%) HG and 492 (35.4%) NF/LG. Throughout follow-up (59.0 months; IQR 39.7 - 82.9 months), 899 patients (64.6%) received aortic valve replacement or TAVI, 551 with HG (73.3%; median time: 12.3 months, IQR 3.5-32.6), 81 with LF/LG AS (55.1%; median time: 28.7 months, IQR 6.8-44.6), and 267 with NF/LG (54.3%; median time: 29.9 months, IQR: 14,1-49,4), with HG AS patients requiring surgery/TAVI earlier than NF/LG (Log-Rank p <0.001) and LF/LG AS patients (p <0.001), without significant differences between the LF/LG and NF/LG (p=0.358). During follow-up, 385 patients died (overall mortality 27.7%): 46 in LF/LG group (31.3%; median time: 50.8 months, IQR: 29.6-75.8), 205 in HG group (27.3%; median time: 56.1 months, IQR: 33.8-83.7) and 134 in NF/LG group (27.2%; median time: 53.19 months, IQR: 31.0 -76.9) with no significant differences among groups (p=0.319). It was observed that the benefit of surgery (in terms of overall mortality risk reduction) in the whole AS population was significant, with HG AS patients benefiting the most (HR: 0.17; 95% CI: 0.12-0.23; p <0.001) followed by LF/LG patients (HR: 0.25; 95% CI: 0.13-0.49; p <0.001) and finally NF/LG (HR: 0.29, 95% CI: 0.20-0.44; p <0.001). Progression of the mean gradient throughout follow-up was greater in low gradient groups: LF/LG and NF/LG compared to HG (LF/LG vs. HG: p=0.022; NF/LG vs. HG: p=0.013) with no significant differences between LF/LG and NF/LG (p=0.426) and considering AVA progression, no significant differences were observed between the LF/LG and HG groups (p=0.452), with this decrease being greater in the NF/LG group than in others (NF/LG vs. HG: p = 0.007; NF/LG vs. LF/LG: p = 0.013). LVEF progression did not differ significantly among groups (LF/LG vs. HG: p = 0.353; NF/LG vs. HG: p = 0.626, LF/LG vs. NF/LG: p = 0.212). Conclusions: Paradoxical LF/LG AS is a rare entity that affects 10.5% of the population. The need for surgery/TAVI in the LF/LG group was lower than in the HG group and similar to NF/LG group, without significant differences in overall and cardiovascular mortality. All patients with significant AS benefited from aortic valve surgery in terms of overall mortality reduction, which was less beneficial in LF/LG AS compared to HG AS. Study of AVA and mean gradient progression revealed an intermediate pattern of LF/LG between the HG and NF/LG groups. Therefore, the findings of the present study conclude that LF/LG has an intermediate clinical profile between the HG and NF/HG groups
