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Tesi etd-12082018-090225

Thesis type
Tesi di dottorato di ricerca
Aortic Valve Stenosis: in the shade of Biomarkers and Advanced imaging. A Translational Journey
Settore scientifico disciplinare
Corso di studi
tutor Prof. Naccarato, Antonio Giuseppe
commissario Prof. Del Prato, Stefano
commissario Prof. De Caterina, Raffaele
commissario Prof.ssa Ghelardi, Emilia
Parole chiave
  • phenotyping
  • systo-diastolic function
  • aortic Stenosis
  • miRNAs
  • sST2
  • echocardiography
  • speckle Tracking
Data inizio appello
Data di rilascio
Riassunto analitico
The following PhD Thesis, is the sum of all my work of the last four years, in the field of advanced echocardiographic imaging and novel biomarkers in valvular heart disease.
In particular, we aimed at a potential redefinition of older patho-physiological paradigms and diagnostic constructs in the field of Aortic Valve Stenosis.
Degenerative Aortic Valve Stenosis represent an epidemic condition, as the first indication to valve surgery in Western world.
Many of the clinical and diagnostic schemes, as reported in Recommendations and Guidelines, stem from old paradigms and incompletely reflect the real and deeper nature of the disease.
With new diagnostic modalities, including imaging and circulating biomarkers, reflecting precise patho-physiological processes, a potential “revolution” is possible.
Our pilot works, together with a revision of the existing literature, are intended as a potential road-map (translational, ie., combining imaging, clinical insight and biomarkers) for a future, modern and tailored approach to the redefinition of this valvular heart disease.
We included three original papers, dealing with micro-RNAs (miRNA-21 and a pool of miRNAs) and sST2, as well as a Letter to Editor (in the field of translational approach to cardiology and valvular disease) and an extensive review in theme of miRNAs and aortica valve disease.
All the material included in this thesis has been published and underwent to peer review mechanisms before publication.

MicroRNAs and Myocardial Fibrosis in Aortic Valve Stenosis, a deep insight on left ventricular remodeling

miRNAs are a huge class of non-coding RNAs that regulate protein-encoding genes (degradation/inhibition of translation). miRNAs are nowadays recognized as regulators of biological processes underneath cardiovascular disorders, including hypertrophy, ischemia, arrhythmias and valvular disease. In particular, circulating miRNAs are promising biomarkers of pathology. This review gives an overview of studies in aortic valve stenosis, exclusively considering myocardial remodelling processes. We searched through literature (till Sept 2016) all studies and reviews involving miRNAs and aortic stenosis (myocardial compart). Although at the beginning of a new era, clear evidences exist on the potential diagnostic and prognostic implementation of miRNAs in the clinical setting. In particular, for aortic stenosis, miRNAs are modulators of myocardial remodelling and hypertrophy. In our experience, here presented in summary, the principal findings of our research were a confirm of the pathophysiological role in aortic stenosis of miRNA-21, in particular, the interdependence between textural miRNA-21 and fibrogenic stimulus induced by an abnormal left ventricular pressure overload. Moreover, circulating miRNA-21 (biomarker) levels are able to reflect the presence of significant myocardial fibrosis.
Thus, the combined evaluation of miRNA-21, a marker of myocardial fibrosis and hypertrophy, together with advanced echocardiographic imaging (2D-speckle tracking), could fulfil many of the existing gaps, renewing older guidelines paradigms, also allowing a better risk prognostic and diagnostic strategies.
Micro-RNA-21 (biomarker) and Global Longitudinal Strain (functional marker) in detection of Myocardial Fibrotic burden in severe Aortic Valve Stenosis: a pilot study

Myocardial fibrosis (MF) is a deleterious consequence of aortic valve stenosis (AVS). Global Longitudinal Strain (GLS) is a novel left ventricular (LV) functional parameter potentially useful to non-invasively estimate MF. MicroRNAs (miRNAs) are non-coding small ribonucleic acids (RNA) modulating genes function, mainly through RNA degradation. miRNA-21 is a biomarker associated with MF in pressure overload.
The aim of the present study was to find an integrated algorithm for detection of MF using a combined approach with both bio- and functional markers.
Thirty-six patients (75.2+/-8 y.o.; 63% Female) with severe AVS and preserved LV ejection fraction (EF), candidate to surgical aortic valve replacement (sAVR) were enrolled. Clinical, bio-humoral evaluation (including plasmatic miRNA-21 collected using specific tubes, PAXgene, for stabilization of peripheral RNA) and a complete echocardiographic study, including GLS and septal strain, were performed before sAVR. Twenty-eight of those patients underwent sAVR and, in 23 of them, an inter-ventricular septum biopsy was performed. Tissues were fixed in formalin and embedded in paraffin. Sections were stained with Hematoxylin and Eosin for histological evaluation and with histochemical Masson trichrome for collagen fibers. The different components were calculated and expressed as micrometers2. To evaluate tissue miRNA components, sections 2-um thick were cut using a microtome blade for each slide. Regression analysis was performed to test association between dependent variable and various predictors included in the model.
Despite a preserved EF (66+/-11%), patients presented altered myocardial deformation parameters (GLS -14,02+/-3.8 %; Septal longitudinal strain, SSL -9.63+/-2.9 %; Septal Longitudinal Strain Rate, SL-Sr -0.58+/-0.17 1/sec; Septal Longitudinal early-diastolic Strain Rate, SL-SrE 0.62+/-0.32 1/sec). The extent of MF showed an inverse association with both GLS and septal longitudinal deformation indices (GLS: R2=0.30; p=0.02; SSL: R2=0.36; p=0.01; SL-Sr: R2=0.39; p<0.001; SL-SrE: R2=0.35; p=0.001). miRNA-21 was mainly expressed in fibrous tissue (p<0.0001). A significant association between MF and plasmatic miRNA-21, alone and weighted for measures of structural (LVMi R2=0.50; p=0.0005) and functional (SSL R2=0.35; p=0.006) remodeling, was found.
In AVS, MF is associated with alterations of regional and global strain. Plasmatic miRNA-21 is directly related to MF and associated with LV structural and functional impairment.

MicroRNAs distribution in different phenotypes of Aortic Stenosis

Aortic valve stenosis (AVS) represents a cluster of different phenotypes, considering gradient and flow pattern. Circulating microRNAs may reflect specific pathophysiological processes and could be useful biomarkers to identify disease.
We assessed 80 patients (81, 76.7-84 years; 46, 57.5% females) with severe AVS. We performed bio-humoral evaluation (including circulating miRNA-1, 21, 29, 133) and 2D-echocardiography. Patients were classified according to ACC/AHA groups (D1-D3) and flow-gradient classification, considering normal/low flow, (NF/LF) and normal/high gradient, (NG/HG).
Patients with reduced ejection fraction were characterized by higher levels of miRNA1 (p=0.003) and miRNA 133 (p=0.03). LF condition was associated with higher levels of miRNA1 (p=0.02) and miRNA21 (p=0.02). Levels of miRNA21 were increased in patients with reduced Global longitudinal strain (p=0.03). LF-HG and LF-LG showed higher levels of miRNA1 expression (p=0.005). At one-year follow-up miRNA21 and miRNA29 levels resulted significant independent predictors of reverse remodeling and systolic function increase, respectively.
Different phenotypes of AVS may express differential levels and types of miRNAs, which may retain a pathophysiological role in pro-hypertrophic and pro-fibrotic processes.

The Integrated Value of sST2 and Global Longitudinal Strain in the Early Stratification of Patients with Severe Aortic Valve Stenosis: a Translational Imaging Approach

Aortic valve stenosis (AVS) is associated with significant myocardial fibrosis (MF). Global longitudinal strain (GLS) is a sensible indicator of systolic dysfunction. ST2 is a member of the interleukin (IL)-1 receptor family and a modulator of hypertrophic and fibrotic responses. We aimed at assessing: a) the association between adverse LV remodeling, LV functional parameters (including GLS) and sST2 level. b) the association between MF (detected by endo-myocardial biopsy) and sST2 in patients with AVS undergoing surgical valve replacement.
22 patients with severe AVS and preserved EF underwent aortic valve replacement. They performed laboratory analysis, including serum ST2 (sST2), echocardiography and inter-ventricular septum biopsy to assess MF (%). We included 10 controls for comparison.
Compared to controls, patients showed higher sST2 levels (p<0.0001). sST2 showed correlation with Age (r=0.58; p=0.0004), E/e’average (r=0.58; p=0.0007), GLS (r=0.61; p=0.0002), LAVi (r=0.51; p=0.003), LVMi (r=0.43; p=0.01), sPAP (r=0.36; p=0.04) and SVi (r=-0.47; p<0.005). GLS was the only independent correlate of sST2 (Multiple R2=0.35; p=0.0004). No correlation was found between MF and sST2.
Patients with severe AVS present elevated sST2 levels. LV GLS resulted the only independent predictor of sST2 levels.