ABSTRACT
IMPORTANCE: Guidelines recommend the use of Dobutamine stress echocardiography (DSE) in patients with low-gradient aortic stenosis (AS) and left ventricular ejection fraction (LVEF) <50%. However, a paucity exists in DSE data when LVEF>35%. OBJECTIVE: To examine the diagnostic accuracy of DSE, in patients with low-gradient AS with a wide range of LVEF and to examine the interaction between the diagnostic accuracy of DSE and LVEF. DESIGN, SETTING AND PARTICIPANTS: Patients with mean-gradient<40 mmHg, AVA<1.0 cm2, and stroke volume index≤35 mL/m2 undergoing DSE and Cardiac Computer Tomography (C-CT) were identified from three prospectively collected patient cohorts, and stratified according to LVEF; LVEF<35%, LVEF 35-50% & LVEF>50%. EXPOSURE: DSE and C-CT was performed on patients with low-gradient AS MAIN OUTCOMES AND MEASURES: Severe AS was defined as AVC score ≥2000 AU among men, and ≥1200 AU for women on C-CT. RESULTS: Of 221 patients included in the study, 78 (35%) presented with LVEF<35%, 67 (30%) with LVEF 35-50%, and 76 (34%) with LVEF>50%. Mean-gradient and Vmax during DSE showed significantly diagnostic heterogeneity between LVEF groups, being most precise when LVEF<35% (both AUC=0.90), albeit with optimal thresholds of 30 mmHg & 377 cm/s, and a limited diagnostic yield in patients with LVEF≥35% (AUC=0.67 & 0.66 in LVEF 35-50% and AUC=0.65 & 0.60 in LVEF≥50%). Using guideline thresholds led to a sensitivity/specificity of 49%/84% for all patients with LVEF<50%. CONCLUSION AND RELEVANCE: While DSE is safe and leads to an increase in stroke volume in patients with low-gradient AS regardless of LVEF, the association between DSE gradients and AS severity assessed by C-CT demonstrates important heterogeneity depending on LVEF, with highest accuracy in patients with LVEF<35%.
ABSTRACT
GATA4 is an essential transcriptional regulator required for gonadal development, differentiation, and function. In the developing testis, proposed GATA4-regulated genes include steroidogenic factor 1 (Nr5a1), SRY-related HMG box 9 (Sox9), and anti-Müllerian hormone (Amh). Although some of these genes have been validated as genuine GATA4 targets, it remains unclear whether GATA4 is a direct regulator of endogenous Amh transcription. We used a CRISPR/Cas9-based approach to specifically inactivate or delete the sole GATA-binding motif of the proximal mouse Amh promoter. AMH mRNA and protein levels were assessed at developmental time points corresponding to elevated AMH levels: fetal and neonate testes in males and adult ovaries in females. In males, loss of GATA binding to the Amh promoter significantly reduced Amh expression. Although the loss of GATA binding did not block the initiation of Amh transcription, AMH mRNA and protein levels failed to upregulate in the developing fetal and neonate testis. Interestingly, adult male mice presented no anatomical anomalies and had no evidence of retained Müllerian duct structures, suggesting that AMH levels, although markedly reduced, were sufficient to masculinize the male embryo. In contrast to males, GATA binding to the Amh promoter was dispensable for Amh expression in the adult ovary. These results provide conclusive evidence that in males, GATA4 is a positive modulator of Amh expression that works in concert with other key transcription factors to ensure that the Amh gene is sufficiently expressed in a correct spatiotemporal manner during fetal and prepubertal testis development.
