Déterminants, mécanismes et conséquences de la dysfonction et du remodelage ventriculaire après remplacement valvulaire aortique : rôle des phénomènes inflammatoires

Abstract : Aortic stenosis (AS) is the most common valvular heart disease (VHD) in Western countries. It causes a chronic increase in left ventricular (LV) afterload characterized by left ventricular hypertrophy (LVH), ischemia and myocardial fibrosis, diastolic dysfunction and long-term heart failure. Regardless of the severity of stenosis, several factors such as obesity, diabetes, insulin resistance seems to impact the LV remodeling in this condition. These metabolic disorders are associated with a pro-inflammatory state, including adipose tissue, involving mediators perceived in cardiomyocyte hypertrophy and myocardial fibrosis. To date, surgical aortic valve replacement (SAVR) is the only option that has shown an impact on mortality. This surgery has become less risky and leads to a significant decrease in the left ventricular mass (LVM) in the first year. Nevertheless, some factors, including the existence of a patient-prosthesis mismatch (PPM), seem to influence this reverse remodeling after surgery, which may explain the persistence of myocardial fibrosis or symptoms after the surgery. We have made the following hypotheses: a) a pro-inflammatory state mediated by epicardial adipose tissue (EAT) and circulating leukocytes would be associated with pathological remodeling in the natural history of AS, b) the existence of a PPM after SAVR would be associated with a poorer prognosis regardless of body weight status, c) the circadian clock would play a role in modulating the myocardial response to a hypertrophic stimulus and myocardial ischemia, d) the onset of postoperative right ventricular (RV) dysfunction, would be associated with poorer prognosis after SAVR. We therefore prospectively included patients with severe AS without LV dysfunction, or another VHD, referred to our Heart Valve Center in Lille University Hospital since 2009 for a first SAVR. Clinical and biological evaluation and pre- and postoperative (before discharge) trans-thoracic echocardiography (TTE) were performed for all patients. In a sub-group of patients, biological samples (blood and TAE) were collected at the time of surgery to perform transcriptomic analysis on EAT and flow cytometry on the circulating blood cells. TTE was also performed 1-year after SAVR in a sub-group and all patients were followed-up for cardiovascular events. We found that: a) the amount of EAT was independently associated with worse LV remodeling in AS but not with the magnitude of reverse remodeling after SAVR. According to our first results, this more severe LV remodeling seems to be associated with dysregulation of genes involved in the adaptive immune response, in the regulation of the immune response and in the activation of T lymphocyte cells and also with a number of circulating leukocytes and monocytes more important, b) the indexed effective orifice area of the aortic prosthesis calculated by TTE with the unique cut-off of 0.85cm²/m² showed the best accuracy to predict major events after SAVR in lean or overweight patients but not in obese, c) perioperative myocardial injury is transcriptionally orchestrated by the circadian clock in patients undergoing SAVR, with poorer tolerance in patients operated on in the morning, d) heart failure is more frequently observed in patients operated on in the morning, unrelated to the occurrence of acute kidney injury after SAVR, e) the early and severe post-operative decline in RV longitudinal function reverses within a year and is not predictive of long-term outcomes after SAVR. Subsequently, we will continue to explore the link between adipose tissue and the natural course of LV remodeling, cardiovascular events after SAVR in particular the impact of circadian variations on the occurrence of heart failure and the RV function after SAVR.
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Augustin Coisne. Déterminants, mécanismes et conséquences de la dysfonction et du remodelage ventriculaire après remplacement valvulaire aortique : rôle des phénomènes inflammatoires. Médecine humaine et pathologie. Université du Droit et de la Santé - Lille II, 2018. Français. ⟨NNT : 2018LIL2S005⟩. ⟨tel-02303036⟩

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