Aortic stenosis Research Papers - Academia.edu (original) (raw)

In presence of aortic stenosis, a jet is produced downstream of the aortic valve annulus during systole. The vena contracta corresponds to the location where the cross-sectional area of the flow jet is minimal. The maximal transvalvular... more

In presence of aortic stenosis, a jet is produced downstream of the aortic valve annulus during systole. The vena contracta corresponds to the location where the cross-sectional area of the flow jet is minimal. The maximal transvalvular pressure gradient (TPG(max)) is the difference between the static pressure in the left ventricle and that in the vena contracta. TPG(max) is highly time-dependent over systole and is known to depend upon the transvalvular flow rate, the effective orifice area (EOA) of the aortic valve and the cross-sectional area of the left ventricular outflow tract. However, it is still unclear how these parameters modify the TPG(max) waveform. We thus derived an explicit analytical model to describe the instantaneous TPG(max) across the aortic valve during systole. This theoretical model was validated with in vivo experiments obtained in 19 pigs with supravalvular aortic stenosis. Instantaneous TPG(max) was measured by catheter and its waveform was compared with the one determined from the derived equation. Our results showed a very good concordance between the measured and predicted instantaneous TPG(max). Total relative error and mean absolute error were on average 9.4+/-4.9% and 2.1+/-1.1 mmHg, respectively. The analytical model proposed and validated in this study provides new insight into the behaviour of the TPG(max) and thus of the aortic pressure at the level of vena contracta. Because the static pressure at the coronary inlet is similar to that at the vena contracta, the proposed equation will permit to further examine the impact of aortic stenosis on coronary blood flow.

The optimal timing of aortic valve replacement (AVR) in patients with severe aortic stenosis (AS) is a source of debate. Moreover, it has been shown previously that prosthesis-patient mismatch (PPM) is an independent predictor of... more

The optimal timing of aortic valve replacement (AVR) in patients with severe aortic stenosis (AS) is a source of debate. Moreover, it has been shown previously that prosthesis-patient mismatch (PPM) is an independent predictor of operative mortality after AVR. The study aim was to assess the effect of the preoperative severity of AS and its interaction with PPM with respect

BackgroundAbnormalities of the aortic root are common in patients with a bicuspid aortic valve. Our aim was to investigate the elastic properties of the aortic root in patients with congenital aortic valvular stenosis (AS) in comparison... more

BackgroundAbnormalities of the aortic root are common in patients with a bicuspid aortic valve. Our aim was to investigate the elastic properties of the aortic root in patients with congenital aortic valvular stenosis (AS) in comparison with age- and gender-matched controls, and to investigate the influence of stenosis severity and aortic size on aortic root elasticity.

The contribution of left ventricular (LV) untwisting to LV suction and early-diastolic filling was previously demonstrated, but this was not yet tested in patients with aortic stenosis (AS). We sought to assess the relationship between LV... more

The contribution of left ventricular (LV) untwisting to LV suction and early-diastolic filling was previously demonstrated, but this was not yet tested in patients with aortic stenosis (AS). We sought to assess the relationship between LV untwisting and LV filling pressures in patients with severe AS and normal left ventricular ejection fraction (LVEF) using speckle tracking echocardiography. Sixty-one consecutive patients (66 +/- 9 years) with severe AS, preserved LVEF (63 +/- 6%), and 40 normal subjects (47 +/- 12 years) were prospectively enrolled. A comprehensive echocardiographic examination was performed in all. LV rotation and twisting were assessed using speckle tracking echocardiography. Peak apical back rotation rate, peak LV untwisting rate, and time intervals from QRS onset (ECG) to each of them were measured. Brain natriuretic peptide (BNP) levels were determined in 30 patients. Patients with AS were older than normal subjects (P < 0.001). LV mass, LA volume, LV fill...

In this study, the fundamental problem of the biomagnetic (blood) fluid flow in a channel with stenosis under the influence of a steady localized magnetic field is studied. The mathematical model used for the formulation of the problem is... more

In this study, the fundamental problem of the biomagnetic (blood) fluid flow in a channel with stenosis under the influence of a steady localized magnetic field is studied. The mathematical model used for the formulation of the problem is consistent with the principles of ferrohydrodynamics (FHD) and magnetohydrodynamics (MHD). Blood is considered as a homogeneous Newtonian fluid and is treated as an electrically conducting magnetic fluid which also exhibits magnetization. For the numerical solution of the problem, which is described by a coupled, non-linear system of PDEs, with appropriate boundary conditions, the stream function–vorticity formulation is adopted. The solution is obtained by the development of an efficient pseudotransient numerical methodology using finite differences. This methodology is based on the development of a semi-implicit numerical technique, transformations and stretching of the grid and proper construction of the boundary conditions for the vorticity. Results concerning the velocity and temperature field, skin friction and rate of heat transfer indicate that the presence of the magnetic field influences the
flow field considerably.

In the present study, a numerical simulation is carried out to investigate the physiologically realistic pulsatile blood flow through an arterial stenosis. A semicircular eccentric stenosis is considered which... more

In the present study, a numerical simulation is carried out to investigate the physiologically realistic pulsatile blood flow through an arterial stenosis. A semicircular eccentric stenosis is considered which is more relevant in cardiovascular system rather than the symmetric one. The degree of stenosis is varied by area from 30% to 70%. The pulsatile flow is represented by eight harmonic components superimposed on the time-mean flow. The Reynolds number is varied from 220 to 800 during the pulsation while the Womersley number was kept fixed at 6.17. Results show that the flow behaviours significantly vary during the pulse period. Moreover, vortex rings are developed asymmetrically and the post stenotic areas are severely affected by the vortex rings at the end of the systolic phase compared to other times. This disturbance is increased with an increase of degree of stenosis.

Aortic valve stenosis (AS) represents the most prevalent valvular defect worldwide. It is a progressive disease with a long latency interval and a poor prognosis after symptoms present. According to current European Society of Cardiology... more

Aortic valve stenosis (AS) represents the most prevalent valvular defect worldwide. It is a progressive disease with a long latency interval and a poor prognosis after symptoms present. According to current European Society of Cardiology guidelines, transcatheter aortic valve implantation (TAVI) is recommended in all patients with severe symptomatic AS and a predicted survival longer than one year, who are not suitable for surgical valve replacement. Despite these recommendations, several studies over the past few years suggest extending these indications towards lower risk AS populations. Otherwise, current available operative risk scores such as Society of Thoracic Surgeons score and EuroSCORE, may offer an incomplete risk assessment; in this setting, the Heart Team plays a crucial role in defining the most appropriate therapeutic strategy in patients with AS. In this review, we aim to discuss the current and future indications for TAVI, analyzing available literature according to patients' profile risk (high/mid/low risk) and other specific conditions (valve-in-valve, bicuspid valve and pure aortic regurgitation).

The fundamental problem of blood flow in a channel with stenosis under the influence of a steady uniform magnetic field is studied. The mathematical model used for the formulation of the problem is consistent with the principles of... more

The fundamental problem of blood flow in a channel with stenosis under the influence of a steady uniform magnetic field is studied. The mathematical model used for the formulation of the problem is consistent with the principles of Magnetohydrodynamics (MHD). Blood is considered as a homogeneous Newtonian fluid and is treated as an electrically conducting magnetic fluid. The finite volume (FV) discretization scheme in curvilinear coordinates is used for the discretization of the system of equations governing the MHD blood flow. For the numerical solution of the problem, which is described by a coupled, nonlinear system of PDEs, with appropriate boundary conditions, the SIMPLE method is adopted. Results concerning
the velocity, pressure, and skin friction indicate that the presence of the magnetic field influences considerably the flow field.

Background: Calcific aortic stenosis (AS) is the most common valve abnormality encountered in developing countries. In the majority of patients, stenosis severity is easily identified by a low valve area and high mean gradient. However, a... more

Background: Calcific aortic stenosis (AS) is the most common valve abnormality encountered in developing countries. In the majority of patients, stenosis severity is easily identified by a low valve area and high mean gradient. However, a subset of patients are found to have a low mean gradient despite a low valve area. These latter types can present as either low ejection fraction (EF) with low gradient (stage D2) or normal EF with low gradient (stage D3). Stage D3 is especially difficult to accurately diagnose.

Background. The recognition that patients with a bi- cuspid aortic valve (BAV) are at risk for aorta-related death (rupture or dissection) has favored composite aor- tic root replacement in BAV patients who undergo aortic valve... more

Background. The recognition that patients with a bi- cuspid aortic valve (BAV) are at risk for aorta-related death (rupture or dissection) has favored composite aor- tic root replacement in BAV patients who undergo aortic valve replacement for valve dysfunction as well as in asymptomatic BAV patients with significant aortic root dilatation. We report the results of Bentall operations in 206 BAV patients during an 18-year interval. Methods. Two hundred six BAV patients (mean, 53 14 years, 84% male) underwent composite aortic root replacement between September 1987 and May 2005. One hundred nine patients (53%) presented with aortic regur- gitation, 24 patients (12%) presented with aortic stenosis, and 55 patients (26%) presented with combined aortic stenosis and aortic regurgitation. Median preoperative aortic diameter was 5.5 cm (range, 3 to 9 cm). Twenty-two patients (11%) underwent urgent or emergent proce- dures; 11 had acute type A dissection (5%). Sixty-one percent had a mechani...

Introduction: Surgical replacement for aortic stenosis is fraught with complications in high-risk patients. Transcatheter techniques may offer a minimally invasive solution, but their comparative effectiveness and safety is uncertain. We... more

Introduction: Surgical replacement for aortic stenosis is fraught with complications in high-risk patients.
Transcatheter techniques may offer a minimally invasive solution, but their comparative effectiveness and
safety is uncertain. We performed a network meta-analysis on this topic.
Methods: Randomized trials on transcatheter aortic valve replacement vs surgery were searched. The primary
outcome was all cause death. Risk estimates were obtained with Bayesian network meta-analytic methods.
Results: Four trials with 1,805 patients were included. After a median of 8 months, risk of death and myocardial
infarction was not different when comparing surgery versus transcatheter procedures, irrespective of
device or access. Conversely, surgery was associated with higher rates of major bleeding (odds ratio vs CoreValve=
3.03 [95% credible interval: 2.23-4.17]; odds ratio vs transfemoral Sapien =1.82 [1.21-2.70]; odds
ratio vs transapical Sapien =2.08 [1.20-3.70]), and acute kidney injury (odds ratio vs CoreValve =2.08 [1.33-
3.32]; odds ratio vs transapical Sapien =2.78 [2.21-99.80]), but lower rates of pacemaker implantation (odds
ratio vs CoreValve =0.41 [0.28-0.59]), and moderate or severe aortic regurgitation (odds ratio vs CoreValve
=0.06 [0.02-0.27]; odds ratio vs Sapien=0.17 [0.02-0.76]). Strokes were less frequent with CoreValve than
with transfemoral Sapien (odds ratio =0.32 [0.13-0.73]) or transapical Sapien (odds ratio =0.33 [0.10-0.93]),
whereas pacemaker implantation was more common with CoreValve (odds ratio vs surgery =2.46 [1.69-3.61];
odds ratio vs transfemoral Sapien =2.22 [1.27-3.85]).
Conclusions: Survival after transcatheter or surgical aortic valve replacement is similar, but there might be differences
in the individual safety and effectiveness profile between the treatment strategies and the individual
devices used in transcatheter aortic valve implantation.