Trajectory of Left Ventricular Remodeling in Children With Valvar Aortic Stenosis Following Balloon Aortic Valvuloplasty.

BACKGROUND: Aortic valve stenosis is the most common type of congenital left ventricular (LV) outflow tract obstruction. Balloon aortic valvuloplasty (BAV) has become the first-line treatment pathway in many centers. Our aim was to assess the trajectory of LV remodeling following BAV in children and its relationship to residual aortic stenosis (AS) and insufficiency (AI). METHODS: Children <18 years of age who underwent BAV for isolated aortic stenosis from 2004 to 2012 were eligible for inclusion. Those with AI before BAV, other complex congenital heart lesions, or <2 accessible follow-up echocardiograms were excluded. Baseline and serial echocardiographic data pertaining to aortic valve and LV size and function were retrospectively collected through December 2017 or the first reintervention. Longitudinal data was assessed using per-patient time profiles with superimposed trend lines using locally estimated scatterplot smoothing. Associations with reintervention or death were also evaluated. RESULTS: Among the 98 enrolled children, the median (interquartile range) age at BAV was 2.8 months (0.2-75). The median (interquartile range) follow-up was 6.8 years (1.9-9.0). Children with predominantly residual AI (n=11) demonstrated progressive increases in their LV end-diastolic dimension Z score within the first 3 years after the BAV, followed by a plateau (P<0.001). Their mean LV circumferential and longitudinal strain values remained within the normal range but lower than in the non-AI group (P<0.001 and P=0.001, respectively). Children with predominantly residual aortic stenosis (n=44) had no changes in LV dimensions but had a rapid early increase in mean LV circumferential and longitudinal strain. The cumulative proportion (95% CI) of reintervention at 5 years following BAV was 33.7% (23.6%-42.4%). CONCLUSIONS: Our study demonstrates that LV remodeling occurs mainly during the first 3 years in children with predominantly residual AI after BAV, with no subsequent significant functional changes over the medium term. These data improve our understanding of expected patient trajectories and thus may inform decisions on the timing of reintervention.

Mitochondrial carrier homolog 2 is necessary for AML survival.

Through a clustered regularly insterspaced short palindromic repeats (CRISPR) screen to identify mitochondrial genes necessary for the growth of acute myeloid leukemia (AML) cells, we identified the mitochondrial outer membrane protein mitochondrial carrier homolog 2 (MTCH2). In AML, knockdown of MTCH2 decreased growth, reduced engraftment potential of stem cells, and induced differentiation. Inhibiting MTCH2 in AML cells increased nuclear pyruvate and pyruvate dehydrogenase (PDH), which induced histone acetylation and subsequently promoted the differentiation of AML cells. Thus, we have defined a new mechanism by which mitochondria and metabolism regulate AML stem cells and gene expression.