Short summary

Aortic stenosis is the leading valve disease in the western world, but the pathophysiology is still unclear. The goal of this study is to investigate, sex-hormonal and genetic differences in the RAA-System and their influence on the development of aortic stenosis. This is done, in a cohort of 170 patients, referred for aortic valve surgery. Furthermore, the influence on the pathophysiology, of antihypertensive medications affecting the RAA-System, will be investigated in a retrospective cohort.

Rationale

1. Background

Although aortic valve stenosis (AS) is the most common heart valve disease in the western world, the pathophysiology is not clearly understood. It is generally accepted that AS associates to a complex process of increased cellularity, lipid accumulation, extracellular matrix deposition, and calcification that leads to narrowing of the valve orifice. As a consequence, a transvalvular pressure gradient is created exposing the left ventricle (LV) to increased pressure. In order to preserve a relative normal wall-stress the LV undergoes a remodeling process with the development of LV hypertrophy, concentric geometry and myocardial fibrosis, although this process is different between genders. As the magnitude of the transvalvular gradient is direct proportional with the valve orifice, the use of gradients has been routine for decades and it has been widely accepted that high gradients (HG) are mandatory in severe AS, when LV ejection fraction (EF) was preserved. However, recently it has been demonstrated that a large proportion of patients demonstrate low gradients (LG) despite AS being severe and preserved LVEF. This partly reflects the flow-dependency of transvalvular gradients, and accordingly it has been suggested to sub-classify severe AS depending on transvalvular gradients and flow-conditions. This novel classification has provided new insights into the pathology of AS, as it has been demonstrated that LG severe AS, occur more often among females, present with different valvular alterations and LV structure and function than patients with HG severe AS. While patients with HG severe AS develop LV hypertrophy with preserved LV cavity dimensions, LG severe AS patients develop smaller LV cavities with reduced compliance with less LV hypertrophy. The cause of these heterogeneous remodeling patterns is not understood, but seems unrelated to increased wall-stress, and it has been proposed that this distinct remodeling process could associate to vascular, genetic, gender or non-valvular factors. The renin-angiotensin-aldosterone system plays a key role in the development of both myocardial fibrosis and LV hypertrophy. In addition, in AS, the aortic valve has been demonstrated to produce several substances among these mast-cell chymase and angiotensin-II potent activators of the renin-angiotensin-aldosterone system. Thus in theory LV remodeling differences between LG and HG severe AS patients could represent differences in valvular pathologies, genetic polymorphisms, medications altering the renin-angiotensin-aldosterone system or differences in sexual hormones. The purpose of this study is to compare differences in valvular, myocardial and genetic RAAS expression in HG AS patients with LG AS.

2. Hypothesis

The study will address four separate hypotheses in patients with severe AS and preserved LVEF.

1) Low-gradient AS is associated with non-valvular comorbidities and the use of medications affecting the renin-angiotensin-aldosterone system

2) Low-gradient AS is associated with differences in valvular genetic expression of mast-cell chymase, Angiotensin-II, ACE, ACE2 and Angiotensin receptor 1 and 2.

3) Low-gradient AS is associated with differences in genetic polymorphisms of renin-angiotensin-aldosterone system.

4) Gender differences in LV remodelling associate with different levels of sexual hormones.

3. Specific objectives

3.1 Study 1 In a retrospective cohort of patients with severe AS and LVEF>50% undergoing aortic valve replacement (AVR) between 2015-2020 to 1. Describe the prevalence of used medications 5 years prior to surgery. 2. Describe the prevalence of comorbidities prior to surgery 3. Describe differences in echocardiography assessed a. Stroke volume index b. LV mass index c. Relative wall-thickness d. Transmitral deceleration time according to different AS patterns based on gradients and flow.

3.2 Study 2 In a prospective cohort of patients with severe AS undergoing AVR to describe 1. Differences in valvular a. Calcification (weight) b. Fibrosis c. Genetic expression of Mastcell chymase, Angiotensin-II, ACE, ACE2 and Angiotensin II receptor type 1 and 2. In patients with NFLG, NFHG and LFLG severe AS and LVEF>50% 2. Differences in myocardial a. LV fibrosis assessed by myocardial biopsy b. Genetic expression of angiotensin-II receptors type 1 and 2 c. Genetic expression of angiotensin-II, mastcell chymase, ACE and ACE2 In patients with NFLG, NFHG and LFLG severe AS and LVEF>50% 3. Differences in genetic polymorphisms of the RAAS, in patients with NFLG, NFHG and LFLG severe AS and LVEF>50% 4. The association of myocardial, valvular and genetic differences with a. LV mass assessed by magnetic resonance imaging b. Fibrosis assessed by magnetic resonance imaging T1-mapping and myocardial biopsy c. Valvular calcification estimated by preoperative CT d. LV longitudinal function assessed by speckle-tracking echocardiography. e. LV diastolic function assessed by speckle-tracking echocardiography f. Biomarkers of elevated filling pressure and fibrosis (NT-proBNP, galectin-3) In patients with NFLG, NFHG and LFLG severe AS and LVEF>50%

3.3 Study 3 Patients in study 2 will be stratified according to gender comparing 1. LV mass and relative wall thickness assessed by echocardiography 2. Extracellular volume, assessed by echocardiography 3. Differences in medications and comorbidities 4. Differences in valvular a. Calcification (weight) b. Fibrosis c. Genetic expression of angiotensin-II and mastcell chymase 5. Prevalence of comorbidities prior to surgery 6. Differences in myocardial a. LV fibrosis assessed by myocardial biopsy b. Genetic expression of angiotensin-II receptors type 1 and 2 c. Genetic expression of angiotensin-II, mastcell chymase, ACE and ACE2 between genders, and the impact of sexual hormones on LV and valvular alterations.

Description of the cohort

Study one is a retrospective study, eligible patients will be patients with severe AS and LVEF>50% who underwent AVR in Odense University Hospital from 2015-2020.

Study two and three is a prospective single center study, eligible patients will be patients with severe AS and LVEF>50% undergoing AVR.

Inclusion criteria: 1. Severe AS (estimated by the local heart team, aortic valve area<1cm2) referred for AVR at the cardiology department at Odense University Hospital 2. Age > 18 years 3. Signed informed consent

4.3 Exclusion criteria. 1. Bicuspid aortic valve. 2. LV systolic dysfunction (LVEF<50%). 3. Patients with concomitant moderate-severe aortic valve regurgitation. 4. Concomitant moderate-severe mitral valve regurgitation. 5. Moderate to severe nephropathy (s-creatinine >200 mmol/l) 6. Unwilling to participate in the study. 7. Claustrophobia. 8. Permanent cardiac devices (pacemaker and ICD)

Data and biological material

Data collected will include: Patient Journal information. Imaging data from CT, MR and Ultrasound. Medical history including medication use. Blood samples and myocardial biopsy.

Collaborating researchers and departments

Department of cardiologi, OUH

• Jordi Sanches Dahl

Department of clinical genetics, OUH

• Mads Thomassen

Department of clinical biochemestry, OUH

• Lars Melholt Rasmussen

Department of molecular medicin, SDU

• Jane Stubbe

Department of medicin, University of Laval, Canada

• Marie-Annick Clavel