Non-invasive determination of left ventricular workload in patients with aortic stenosis using magnetic resonance imaging and Doppler echocardiography.

Early detection and accurate estimation of aortic stenosis (AS) severity are the most important predictors of successful long-term outcomes in patients. Current clinical parameters used for evaluation of the AS severity have several limitations including flow dependency. Estimation of AS severity is specifically challenging in patients with low-flow and low transvalvular pressure gradient conditions.

Discrepancies between cardiovascular magnetic resonance and Doppler echocardiography in the measurement of transvalvular gradient in aortic stenosis: the effect of flow vorticity.

Background: Valve effective orifice area EOA and transvalvular mean pressure gradient (MPG) are the most frequently used parameters to assess aortic stenosis (AS) severity. However, MPG measured by cardiovascular magnetic resonance (CMR) may differ from the one measured by transthoracic Doppler-echocardiography (TTE). The objectives of this study were: 1) to identify the factors responsible for the MPG measurement discrepancies by CMR versus TTE in AS patients; 2) to investigate the effect of flow vorticity on AS severity assessment by CMR; and 3) to evaluate two models reconciling MPG discrepancies between CMR/TTE measurements.

Accuracy of Doppler-echocardiographic parameters for the detection of aortic bileaflet mechanical prosthetic valve dysfunction.

Aims: In vitro and in vivo studies were performed to evaluate the diagnostic accuracy of the different Doppler-echocardiographic parameters proposed in the American Society of Echocardiography guidelines to identify dysfunction of bileaflet mechanical valves (BMV) in the aortic position.

Methods And Results: Two models of BMV (St Jude HP, MCRI On-X) of different sizes (21;23;25;27 mm) were tested in vitro under a wide range of cardiac outputs (3-7 L/min). The motion of one or both leaflets was restricted to induce a mild (25% restriction in total valve orifice area) and moderate-to-severe (50% restriction in total valve area).

Effect of concomitant asymmetric septal hypertrophy when assessing the severity of aortic valve stenosis: an in-vitro study.

Background And Aim Of The Study: Aortic valve stenosis (AS) is an important cardiovascular disease that affects between 2% and 7% of the elderly population in industrialized countries. AS often coexists with asymmetric septal hypertrophy (ASH), which is generally caused by a protrusion of the hypertrophied left ventricular outflow tract (LVOT) just below the aortic valve. The study aim was to determine, based on measurement of the aortic valve effective orifice area (EOA), if ASH might potentially interfere with the assessment of AS severity.

Characterization of fracture toughness exhaustion in pig aorta.

Background: Spontaneous rupture of the aorta (SRA) without aneurysm, dissection, inflammation or infection of the aortic wall can be of two types: traumatic and non-traumatic. SRA is most of the time a fatal event. Consequently, it is important to understand the conditions which lead to the aortic rupture, and, in the case of non-traumatic SRA, to predict the temporal likelihood of rupture.

A simple non-invasive method to predict the mitral valve geometric orifice area after edge-to-edge repair.

Background And Aim Of The Study: The edge-to-edge repair (EtER) technique consists of anchoring the free edge of the diseased leaflet of the mitral valve to the corresponding edge of the opposing leaflet. When the middle sections of the leaflets are sutured, a 'double-orifice' (DO) mitral valve is artificially created. The main consequence of this technique is that mitral valve geometric orifice area (MGOA) is sensibly reduced and a functional mitral stenosis might be created.

Optimization of Doppler echocardiographic velocity measurements using an automatic contour detection method.

Intra- and interobserver variability in Doppler echocardiographic velocity measurements (DEVM) is a significant issue. Indeed, imprecisions of DEVM can lead to diagnostic errors, particularly in the quantification of the severity of heart valve dysfunctions. To reduce the variability and rapidity of DEVM, we have developed an automatic method of Doppler velocity wave contour detection, based on active contour models.

Impairment of coronary flow reserve in aortic stenosis.

Coronary flow reserve (CFR) is markedly reduced in patients with severe aortic valve stenosis (AS), but the exact mechanisms underlying this impairment of CFR in AS remain unclear. Reduced CFR is the key mechanism leading to myocardial ischemia symptoms and adverse outcomes in AS patients. The objective of this study was to develop an explicit mathematical model formulated with a limited number of parameters that describes the effect of AS on left coronary inflow patterns and CFR.

Influence of wall compliance on hemodynamics in models of abdominal aortic aneurysm.

Purpose: To determine complementary criteria to existing morphological criteria, which are not reliable but are used to justify surgical intervention to treat abdominal aortic aneurysm (AAA).

Methods: An experimental study was conducted in which 2 models of AAA, 1 rigid and 1 soft, were used to study the influence of compliance on aneurysm dynamics. The heart rate was 70 beats per minute, and the mean flow rate was 1.

Flow behaviour in an asymmetric compliant experimental model for abdominal aortic aneurysm.

An experimental study was carried out on asymmetrical abdominal aortic aneurysm (AAA) to analyse the physiological flows involved. Velocity measurements were performed using particle image velocimetry. Resting and exercise flow rates were investigated in models with rigid and compliant walls to assess the parameters affecting the flow behaviour.