Prevalence and prognostic implications of different aetiologies of low flow aortic stenosis

Background: The prevalence and prognostic implications of low-flow (LF) aetiologies in aortic stenosis (AS) are unknown. This study aimed to characterize the specific causes of LF, their prevalence, and prognostic significance. Methods: In 408 patients with severe LFAS included, the aetiology of LF was identified. The primary endpoint was the composite of all-cause death and hospitalizations for heart failure (HF) up to 36 months. Secondary endpoints included individual components of the primary endpoint and cardiovascular mortality. Results: The most common LF cause was reduced LVEF (n = 228, 55.9%), while preserved LVEF included five aetiologies: (1)mixed aetiologies (n = 65, 36.1%), (2)small LV cavity (n = 58, 32.2%), (3)significant isolated mitral regurgitation (n = 39, 21.7%), (4)significant isolated tricuspid regurgitation (n = 13, 7.2%), (5)significant isolated mitral stenosis (n = 5, 2.8%). Over a median follow-up of 15 (IQR 6 – 36) months obtained in 302 patients, 159 (52.6%) reached the primary composite endpoint, 108 (35.8%) died and 91 (30.8%) were hospitalized due to HF. LF aetiology was not associated with outcomes. Independent predictors of the primary endpoint were severe MR (adj.HR 1.71, p = 0.04) and TR (adj.HR 1.47, p = 0.04). Aortic valve replacement (adj.HR 0.76, p < 0.001) and mean transvalvular gradient ≥ 40 mmHg (adj.HR 0.39, p < 0.001) were protective. Conclusions: The main cause of LFAS is reduced LVEF, while in preserved LVEF mixed causes and small LV volume prevailed, without association with the outcome. Severe mitral and tricuspid regurgitation were strongly associated with worse outcomes, while valve replacement and mean transvalvular gradient ≥ 40 mmHg emerged as protective factors.