Background: Inflammation plays a significant role in the pathogenesis of aortic stenosis. This study aimed to investigate the prognostic value of the monocyte-HDL cholesterol ratio (MHR), a new inflammatory marker, in severe aortic stenosis (AS) patients who underwent transcatheter aortic valve replacement (TAVR). Methods: A total of 125 patients with severe AS who underwent TAVR were assessed. Clinical, echocardiographic and laboratory data relevant to the research were retrospectively obtained from the patients’ records. The MHR was determined by dividing the absolute monocyte count by the HDL-C value. The primary endpoints were overall and cardiovascular mortality. Results: During a median follow-up time of 39 months, primary endpoints were developed in 51 (40.8%) patients (overall mortality) and 21 (16.8%) patients (cardiovascular mortality). A receiver operating characteristic (ROC) analysis showed that by using a cut-off level of 16.16, the MHR predicted the all-cause mortality with a sensitivity of 50.9% and specificity of 89.1%. In predicting cardiovascular mortality, the MHR exhibited a sensitivity of 80.9% and specificity of 70.1% when a cut-off level of 13.56 was used. In the multivariate analysis, the MHR (p < 0.0001; 95% CI: 1.06–1.15) and atrial fibrillation (p = 0.018; 95% CI: 1.11–3.38) were found to be significant predictors of overall mortality. Conclusions: This study showed a significant elevation in the MHR among patients who experienced all-cause and cardiovascular mortality and this ratio emerged as an independent predictor of all-cause death in patients with severe AS undergoing TAVR.

The involvement of the serotoninergic system in the pathogenesis of calcific aortic stenosis introduced a novel dimension to our understanding of this complex cardiovascular condition. This study aimed to assess serotonin (5-HT) and its main metabolite, 5-Hydroxyindoleacetic acid (5-HIAA) in patients with severe aortic valve stenosis (AS). The study employed a case–control design, including 76 patients who underwent transthoracic echocardiography, computed tomography (CT), and peripheral blood sampling. Serum concentrations of 5-HT and 5-HIAA were quantified using enzyme-linked immunosorbent assay (ELISA). The severe aortic valve stenosis group exhibited significantly elevated levels of 5-HT and 5-HIAA compared to the control group (5-HT 1066.5 ng/mL (IQR = 961.9–1112 ng/mL) vs. 977.4 ng/mL (IQR = 394.3–1097.9 ng/mL); p = 0.034 and 5-HIAA 57 ± 12.7 ng/mL vs. 47.5 ± 15.3 ng/mL; p = 0.004, respectively). Receiver operating characteristic (ROC) analysis revealed that 5-HT predicted severe AS with a sensitivity of 73.7% and specificity of 50% at a cut-off level > 973.5 ng/mL, whereas 5-HIAA exhibited a sensitivity of 86.8% and specificity of 47.4% when a cut-off level > 45.49 ng/mL was used. This study showed a significant elevation in the 5-HT and 5-HIAA among patients with severe AS, further supporting the potential involvement of the peripheral serotonergic system in the pathophysiology of this condition.