Biomedical subjects

Damien Coisne

Publications and source records attributed to Damien Coisne.

8 recordsLinked to original sources

PubMed2006

Computational approach to estimating the effects of blood properties on changes in intra-stent flow.

In this study various blood rheological assumptions are numerically investigated for the hemodynamic properties of intra-stent flow. Non-newtonian blood properties have never been implemented in blood coronary stented flow investigation, although its effects appear essential for a correct estimation and distribution of wall shear stress (WSS) exerted by the fluid on the internal vessel surface. Our numerical model is based on a full 3D stent mesh. Rigid wall and stationary inflow conditions are applied. Newtonian behavior, non-newtonian model based on Carreau-Yasuda relation and a characteristic newtonian value defined with flow representative parameters are introduced in this research. Non-newtonian flow generates an alteration of near wall viscosity norms compared to newtonian. Maximal WSS values are located in the center part of stent pattern structure and minimal values are focused on the proximal stent wire surface. A flow rate increase emphasizes fluid perturbations, and generates a WSS rise except for interstrut area. Nevertheless, a local quantitative analysis discloses an underestimation of WSS for modelisation using a newtonian blood flow, with clinical consequence of overestimate restenosis risk area. Characteristic viscosity introduction appears to present a useful option compared to rheological modelisation based on experimental data, with computer time gain and relevant results for quantitative and qualitative WSS determination.

Animals↗

PubMed2005

Tissue Doppler echocardiographic quantification. Comparison to coronary angiography results in Acute Coronary Syndrome patients.

BACKGROUND: Multiples indices have been described using tissue Doppler imaging (DTI) capabilities. The aim of this study was to assess the capability of one or several regional DTI parameters in separating control from ischemic myocardium. METHODS: Twenty-eight patients with acute myocardial infarction were imaged within 24-hour following an emergent coronary angioplasty. Seventeen controls without any coronary artery or myocardial disease were also explored. Global and regional left ventricular functions were assessed. High frame rate color DTI cineloop recordings were made in apical 4 and 2-chamber for subsequent analysis. Peak velocity during isovolumic contraction time (IVC), ejection time, isovolumic relaxation (IVR) and filling time were measured at the mitral annulus and the basal, mid and apical segments of each of the walls studied as well as peak systolic displacement and peak of strain. RESULTS: DTI-analysis enabled us to discriminate between the 3 populations (controls, inferior and anterior AMI). Even in non-ischemic segments, velocities and displacements were reduced in the 2 AMI populations. Peak systolic displacement was the best parameter to discriminate controls from AMI groups (wall by wall, p was systematically < 0.01). The combination IVC + and IVR< 1 discriminated ischemic from non-ischemic segments with 82% sensitivity and 85% specificity. CONCLUSION: DTI-analysis appears to be valuable in ischemic heart disease assessment. Its clinical impact remains to be established. However this simple index might really help in intensive care unit routine practice.

Acute Disease↗

PubMed2005

Quantitative regional analysis of left atrial function by Doppler tissue imaging-derived parameters discriminates patients with posterior and anterior myocardial infarction.

BACKGROUND: Doppler tissue imaging can now be used for the assessment of left atrial (LA) function. LA function was evaluated by this technique in a group of patients hospitalized for acute myocardial infarction and in a control population. METHODS: Patients were all prospectively imaged with a scanner. To study the LA, a region of interest was located in the proximal part of the lateral and septal LA walls. Doppler tissue imaging, tissue tracking, strain, and delays were recorded. RESULTS: In all, 12 patients with posterior (age 54 +/- 9 years) and 13 with anterior (age 64 +/- 16 years) acute myocardial infarction, along with 16 control patients (age 54 +/- 9 years), were analyzed. Early diastolic septal velocity was found to be the best parameter for discriminating among the 3 groups. Peak strain was also relevant and did not correlate with left ventricular function. CONCLUSIONS: LA is accessible to Doppler tissue imaging analysis. Strain can quantify LA function relatively independently of left ventricular function, and may provide new insights on LA function.

Aged↗

PubMed2004

Anatomic M-mode, a pertinent tool for the daily practice of transthoracic echocardiography.

OBJECTIVES: We sought to compare anatomic M-mode (AMM), a new echocardiographic postprocessing option, and conventional M-mode (CMM) using fundamental imaging and tissue harmonic imaging. METHODS: Transthoracic echocardiography was performed in 15 selected patients to analyze the reproducibility of AMM and in 47 patients to assess its clinical value versus CMM. Acquisitions were performed successively: CMM fundamental imaging; CMM tissue harmonic imaging; tissue harmonic imaging cineloops for AMM; and fundamental imaging cineloops for AMM. Quantitative analysis was performed offline. The angle alpha between the CMM line and the septal endocardial interface was calculated and the expected percentage of error in measuring left ventricular diameter was derived. RESULTS: AMM analysis was reproducible. Optimal AMM full echocardiographic definition was obtainable in 77% of the population, whereas CMM was optimal for 49% because of scan line misalignment, causing a measurement overestimation exceeding 5%. CONCLUSION: The ability with AMM to reduce the alpha angle to 0 degrees and, thus, avoid overestimation of left ventricular dimensions might improve follow-up in several pathologic conditions.

Adolescent↗

PubMed2004

DECOPI (DEsobstruction COronaire en Post-Infarctus): a randomized multi-centre trial of occluded artery angioplasty after acute myocardial infarction.

AIM: To determine whether late recanalization of an occluded infarct artery after acute myocardial infarction is beneficial. METHODS AND RESULTS: Two hundred and twelve patients with a first Q-wave myocardial infarction (MI) and an occluded infarct vessel were enrolled. After coronary and left ventricular contrast angiography, patients were randomized to percutaneous revascularization (PTCA, n=109), carried out 2-15 days after symptom onset or medical therapy (n=103). The primary endpoint was a composite of cardiac death, non-fatal MI, or ventricular tachyarrhythmia. The majority had single-vessel disease and less than one-third had involvement of the left anterior descending artery. The use of pharmacological therapy was high in both groups. At six months, left ventricular ejection fraction was 5% higher in the invasive compared with the medical group (P=0.013) and more patients had a patent artery (82.8% vs 34.2%, P<0.0001). Restenosis was seen in 49.4% of patients in the PTCA group. At a mean of 34 months of follow-up, the occurrence of the primary endpoint was similar in the medical and PTCA groups (8.7% vs 7.3% respectively, P=0.68), but the overall costs were higher for PTCA. The secondary endpoint combining the primary endpoint with admission for heart failure was also similar between groups (12.6% vs 10.1% in the medical and PTCA groups, respectively, P=0.56). CONCLUSIONS: Systematic late PTCA of the infarct vessel was associated with a higher left ventricular ejection fraction at six months, no difference in clinical outcomes, and higher costs than medical therapy. These results must be interpreted with caution given the small size and low risk of the population.

Adult↗

PubMed2003

Experimental study of laminar blood flow through an artery treated by a stent implantation: characterisation of intra-stent wall shear stress.

The stimulation of endothelial cells by arterial wall shear stress (WSS) plays a central role in restenosis. The fluid-structure interaction between stent wire and blood flow alters the WSS, particularly between stent struts. We have designed an in vitro model of struts of an intra-vascular prosthesis to study blood flow through a 'stented' section. The experimental artery consisted of a transparent square section test vein, which reproduced the strut design (100x magnifying power). A programmable pump was used to maintain a steady blood flow. Particle image velocimetry method was used to measure the flow between and over the stent branches, and to quantify WSS. Several prosthesis patterns that were representative of the total stent strut geometry were studied in a greater detail. We obtained WSS values of between -1.5 and 1.5Pa in a weak SS area which provided a source of endothelial stimulation propitious to restenosis. We also compared two similar patterns located in two different flow areas (one at the entry of the stent and one further downstream). We only detected a slight difference between the weakest SS levels at these two sites. As the endothelial proliferation is greatly influenced by the SS, knowledge of the SS modification induced by the stent implantation could be of importance for intra-vascular prostheses design optimisation and thus can help to reduce the restenosis incidence rate.

Arteries↗

PubMed2003

Determination of the optimal region for interaliasing distance measurement for flow regurgitant rate calculation: a fluid simulation study.

BACKGROUND: Color Doppler imaging of the convergent region is promising for quantifying valvular regurgitation. Nevertheless, proximal isovelocity surface area method has limitations. We sought to determine the optimal localization to measure the most precise flow rate using a new approach: the interaliasing distance. METHODS: A finite volume-based program was used to perform simulations in unsteady flow conditions. Different instantaneous flow rates, leaflet angles, and orifice sizes were tested reproducing physiologic conditions. Relative difference between actual and interaliasing distance flow rate was calculated for each configuration. RESULTS: The relationship between the relative error and the aliasing velocity location was described by a third-order polynomial equation. The magnitude of relative error is a function of the flow rate, orifice size, and leaflet angle. CONCLUSION: The optimal distance from the orifice to measure the interaliasing distance was when the closer aliasing was between 4 and 8 mm from the orifice.

Atrial Function↗

PubMed2002

Quantitative assessment of regurgitant flow with total digital three-dimensional reconstruction of color Doppler flow in the convergent region: in vitro validation.

BACKGROUND: This study was designed to develop and test a total digital 3-dimensional (3D) color flow map reconstruction for proximal isovelocity surface area (PISA) measurement in the convergent region. METHODS: Asymmetric flow convergent velocity field was created in an in vitro pulsatile model of mitral regurgitation. Image files stored in the echocardiographic scanner memory were digitally transferred to a computer workstation, and custom software decoded the file format, extracted velocity information, and generated 3D flow images automatically. PISA and volume flow rate were calculated without geometric assumption. For comparison, regurgitant volume was also calculated, using continuous wave Doppler, 2-dimensional (2D), and M-mode color flow Doppler with the hemispheric approach. RESULTS: Flows from 3D digital velocity profiles showed a closed, excellent relation with actual flow rates, especially for instantaneous flow rate. Regurgitant volume calculated with the 3D method underestimated the actual flow rate by 2.6%, whereas 2D and the M-mode method show greater underestimation (44.2% and 32.1%, respectively). CONCLUSION: Our 3D reconstruction of color flow Doppler images gives more exact information of the flow convergent zone, especially in complex geometric flow fields. Its total digital velocity process allows accurate measurement of convergent surface area and improves quantitation of valvular regurgitation.

Blood Flow Velocity↗