Carine Guivier-Curien

Examination of factors in type I endoleak development after thoracic endovascular repair

OBJECTIVE The objective of this study was to assess the effects of operative indication, anatomy, and stent graft on type I endoleak occurrence after thoracic endovascular aortic repair. METHODS A retrospective review was conducted of patients admitted for thoracic endovascular aortic repair between 2007 and 2013. All computed tomography angiography imaging was analyzed for the presence of endoleak and measurement of diameters and lengths. Variables studied included underlying disease, emergency, achieved aortic neck length, difference between proximal and distal neck diameters, landing zone 2, and stent graft characteristics (diameter, number, type of device, oversizing degree, and covered aorta length). RESULTS The study population involved 84 patients (mean age, 56 years; range, 17-94 years) who were treated for thoracic aortic aneurysm (TAA) (n = 29; 34.5%), traumatic aortic rupture (n = 27; 32%), type B aortic dissection (n = 19; 22.5%), intramural hematoma (n = 2; 2%), penetrating aortic ulcer (n = 5; 6%), and aortoesophageal fistula (n = 2; 2%). Of these, 60 patients (71.5%) were treated emergently and 24 (28.5%) electively. Primary type I endoleak was noted in eight patients (9.5%), of which two resolved spontaneously. After a mean follow-up of 32 months (range, 3-76 months), secondary type I endoleak was detected in four patients (4.5%). All of them occurred after emergent TAA treatment. Comparison between emergent and elective groups revealed no significant differences in neck length (19.5 mm vs 26.5 mm; P = .197), oversizing degree (11.1% vs 10.9%; P = .811), or endoleak rates (13.3% vs 8.3%; P = .518). Hemorrhagic shock was not predictive of endoleak (P = .483). Cox regression analysis of the different anatomic and stent graft-related factors revealed short proximal landing zone as the unique independent predictor of type I endoleak (hazard ratio, 0.89; 95% confidence interval, 0.81-0.99; P = .032). CONCLUSIONS Endoleak risk seems not to be increased by an emergency setting. However, the relatively high rate of late endoleak observed after emergent TAA repair advocates for close follow-up, contrary to traumatic aortic rupture. Furthermore, regardless of the pathologic process, a longer proximal landing zone is likely to guarantee early and late success.

Risk Factor Analysis of Bird Beak Occurrence after Thoracic Endovascular Aortic Repair

OBJECTIVES The aim was to analyze the role played by anatomy and stent graft in the incidence of incomplete apposition to aortic arch. METHODS Between 2007 and 2014 data including available and suitable computed tomographic angiography (CTA) imaging of patients who had undergone thoracic endovascular aortic repair were reviewed. The study included 80 patients (65 men, 54 ± 21 years) treated for traumatic aortic rupture (n = 27), thoracic aortic aneurysm (n = 15), type B aortic dissection (n = 24), penetrating aortic ulcer (n = 5), intramural hematoma (n = 2), aorto-oesophageal fistula (n = 2), and aortic mural thrombus (n = 5). Pre- and post-operative CTA images were analyzed to characterize bird beak in terms of length and angle, and to calculate aortic angulation within a 30 mm range at the proximal deployment zone. RESULTS Bird beak configuration was detected in 46 patients (57%): mean stent protrusion length was 16 mm (range: 8-29 mm) and mean bird beak angle was 20° (range: 7-40°). The bird beak effect was significantly more frequent after traumatic aortic rupture treatment (p = .05) and in landing zone 2 (p = .01). No influence of either stent graft type or generation, or degree of oversizing was observed (p = .29, p = .28, p = .81 respectively). However, the mean aortic angle of patients with bird beak was higher in the Pro-form group than that in the Zenith TX2 group (62° vs. 48°, p = .13). Multivariate analysis identified the aortic angle of the deployment zone as the unique independent risk factor of malapposition (HR = 1.05, 95% CI 1-1.10, p = .005). The cutoff value of 51° was found to be predictive of bird beak occurrence with a sensitivity of 58% and a specificity of 85%. CONCLUSIONS Assessment of proximal landing zone morphology to avoid deployment zones generating an aortic angle of over 50° can be recommended to improve aortic curvature apposition with the current available devices.

Computed tomography, histological and ultrasonic measurements of adolescent scoliotic rib hump geometrical and material properties

In Adolescent Idiopathic Scoliosis (AIS), numerical models can enhance orthopaedic or surgical treatments and provide reliable insights into the mechanism of progression. Computational methods require knowledge of relevant parameters, such as the specific geometrical or material properties of the AIS rib, about which there is currently a lack of information. The aim of our study was to determine the geometrical and material properties (Youngs modulus [E] and Poissons ratio [ν]) for AIS rib bones. Twelve ribs extracted during gibbectomy on 15 and 17 year old girls were tested using computed tomography (CT) scanner, histology and ultrasonic scanner. The mean porosity (± standard deviation (SD)) is 1.35 (±0.52)% and the mean (±SD) bone mineral density is 2188 (±19)mmHA/cc. The cortical part of the AIS rib hump is found to be thicker than physiological values in the literature. To mimic the rib hump for an AIS girl, our results suggest that ribs should be modeled as hollow circular cylinders with a 10.40 (±1.02)mm external radius and 7.56mm (±0.75) internal radius, and material properties with a mean E of 14.9GPa (±2.6) and a mean ν of 0.26 (±0.08).

Localized Transvalvular Pressure Gradients in Mitral Bileaflet Mechanical Heart Valves and Impact on Gradient Overestimation by Doppler

BACKGROUND It has been reported that localized high velocity may be recorded by continuous-wave Doppler interrogation through the smaller central orifices of bileaflet mechanical heart valves (BMHV) and that this may result in overestimation of the transvalvular pressure gradient (TPG). However, the prevalence and clinical relevance of this phenomenon remain unclear, particularly for BMHVs in the mitral position. The objective of this in vitro study was to assess the presence and magnitude of localized high velocity in mitral BMHVs as well as its impact on TPG overestimation by Doppler. METHODS Nine BMHVs were tested under nine different flow conditions (volumes and flow waveforms) in a simulator specifically designed to assess mitral valve hemodynamics. Flow velocity was measured at three different locations (leading edge, midleaflets, and trailing edge) within the central and lateral orifices of the BMHVs using pulsed-wave Doppler. TPG was measured by pulsed-wave and continuous-wave Doppler and by catheterization. RESULTS The maximum flow velocity occurred within the central orifice of the BMHV in 61% of the 81 tested conditions. This locally higher velocity within the central orifice predominantly occurred at the leading edge of the prosthesis. Doppler overestimated mean TPG by an average of 5% to 10% compared with catheterization. The magnitude of the localized high velocity and ensuing overestimation of TPG by Doppler was more important at higher mitral flow volumes (P < .0001) as well as in BMHVs with smaller internal ring diameters (P < .0001). CONCLUSIONS This study shows that the flow velocity distribution within the three orifices of mitral BMHVs is not uniform and that higher velocity occurs more frequently, but not always, within the inflow aspect of the central orifice. In most mitral BMHVs and flow conditions, this localized high-velocity phenomenon causes small overestimation of TPGs (<2 mm Hg and <10%) by Doppler and is thus not clinically relevant. However, in small mitral BMHVs exposed to high flow rates, the overestimation of TPG due to localized high velocity could become more important and overlap with the range of gradients found in patients with prosthesis dysfunction or prosthesis-patient mismatch.

Determination of mechanical properties of cortical bone using AFM under dry and immersed conditions.

Bone is a hierarchically organized material. At the nanoscopic scale, bone is primarily composed of collagen fibres (diameter = 20-40 nm) and apatite crystals (dimension = 50 x 25 x 3 nm). The mechanical characteristics of bone, like strength, stiffness and Young modulus, are derived from these qualitative and quantitative part of these nanoscale constituents. Atomic force spectroscopy is a technique derived from Atomic Force Microscopy (AFM) which can be used to realize nano-indentation measurements and determine the nanomechanical properties of elements. This technique is increasingly used by research teams (Wallace, 2012). Today, for practical reasons, measurements on bones are mainly performed on dry samples in air and/or on samples included in resin. However, when attempting to mechanically characterize a biological tissue, physiological test conditions are necessary. The aim of this study is therefore to measure the impact of hydration on the nanomechanical properties of bovine bones. Samples were analyzed in both air and PBS solutions.

Biaxial tensile tests of the porcine ascending aorta

One of the aims of this work is to develop an original custom built biaxial set-up to assess mechanical behavior of soft tissues. Stretch controlled biaxial tensile tests are performed and stereoscopic digital image correlation (SDIC) is implemented to measure the 3D components of the generated displacements. Using this experimental device, the main goal is to investigate the mechanical behavior of porcine ascending aorta in the more general context of human ascending aorta pathologies. The results highlight that (i) SDIC arrangement allows accurate assessment of displacements and so stress strain curves, (ii) porcine ascending aorta has a nearly linear and anisotropic mechanical behavior until 30% of strain, (iii) porcine ascending aorta is stiffer in the circumferential direction than in the longitudinal one, (iv) the material coefficient representing the interaction between the two loading directions is thickness dependent, (v) taking into account the variability of the samples the stress values are independent of the stretch rate in the range of values from 10(-3) to 10(-1)s(-1) and finally, (vi) unlike other segments of the aorta, 4-month-old pigs ascending aorta is definitely not a relevant model to investigate the mechanical behavior of the human ascending aorta.

Mitral valve-in-valve hemodynamic performance : an in vitro study

OBJECTIVES The valve-in-valve (VinV) procedure may be used in high-risk patients with failed mitral surgical bioprostheses. The objective of this in vitro study was to assess the hemodynamic function of different VinV configurations. METHODS A double activation duplicator was used to test 11 valve configurations (surgical bioprostheses alone) and 15 VinV configurations (Sapien [Edwards Lifesciences, Irvine, Calif] implanted within the surgical bioprosthesis) under 8 different hemodynamic conditions. The internal orifice diameter (IOD) of the surgical bioprosthesis was measured with a Smartscope (OGP Multi Sensor Measuring Instruments, Singapore). RESULTS The VinV procedure was associated with significant deterioration in antegrade hemodynamic parameters compared with valve configuration (effective orifice area, 1.51 ± 0.21 cm(2) vs 1.65 ± 0.37 cm(2); P < .001 and regurgitant fraction, 11.5% ± 7.2% vs 4.8% ± 3.8%; P < .001). Among the 120 tested experimental VinV situations, moderate or greater mitral stenosis occurred in 52 situations and mild or greater regurgitation occurred in 28 situations. The IOD of the surgical bioprosthesis was the main independent determinant of effective orifice area and regurgitant fraction. An IOD < 22 mm was associated with higher risk of significant mitral stenosis, particularly when the oversizing was >20%, and IOD > 23 mm was associated with higher risk of paravalvular regurgitation when oversizing was <8%. CONCLUSIONS This in vitro study shows that VinV within mitral surgical bioprostheses provides satisfactory hemodynamic results in the majority of patients. However, significant mitral stenosis is more likely to occur when the IOD of the surgical bioprosthesis is <22 mm, and particularly when the percentage of oversizing is >20%. Significant paravalvular regurgitation is rare and occurs with larger IODs and lower percentage of oversizing (8%).

Are the current Doppler echocardiography criteria able to discriminate mitral bileaflet mechanical heart valve malfunction? An in vitro study.

Malfunction of bileaflet mechanical heart valves in the mitral position could either be due to patient-prosthesis mismatch (PPM) or leaflet obstruction. The aim of this article is to investigate the validity of current echocardiographic criteria used for diagnosis of mitral prosthesis malfunction, namely maximum velocity, mean transvalvular pressure gradient, effective orifice area, and Doppler velocity index. In vitro testing was performed on a double activation left heart duplicator. Both PPM and leaflet obstruction were investigated on a St. Jude Medical Master. PPM was studied by varying the St. Jude prosthesis size (21, 25, and 29 mm) and stroke volume (70 and 90 mL). Prosthesis leaflet obstruction was studied by partially or totally blocking the movement of one valve leaflet. Mitral flow conditions were altered in terms of E/A ratios (0.5, 1.0, and 1.5) to simulate physiologic panel of diastolic function. Maximum velocity, effective orifice area, and Doppler velocity index are shown to be insufficient to distinguish normal from malfunctioning St. Jude prostheses. Doppler velocity index and effective orifice area were 1.3 ± 0.49 and 1.83 ± 0.43 cm(2) for testing conditions with no malfunction below the 2.2 and 2 cm(2) thresholds (1.19 cm(2) for severe PPM and 1.23 cm(2) for fully blocked leaflet). The mean pressure gradient reached 5 mm Hg thresholds for several conditions of severe PPM only (6.9 mm Hg and mean maximum velocity value: 183.4 cm/s) whereas such value was never attained in the case of leaflet obstruction. In the case of leaflet obstruction, the maximum velocity averaged over the nine pulsed-wave Doppler locations increased by 38% for partial leaflet obstruction and 75% for a fully blocked leaflet when compared with normal conditions. Current echocardiographic criteria might be suboptimal for the detection of bileaflet mechanical heart valve malfunction. Further developments and investigations are required in order to further improve current guidelines.

Geometrical orifice area compared to effective orifice area of valvular mitral bioprosthesis: in vitro study

The relation between the geometrical orifice area (GOA) and the effective orifice area (EOA) of mitral bioprosthesis has been previously studied in both in vitro and clinical studies. Although GOA ...

Thoracic aorta morphometry and endograft deployment

First used to deal with abdominal aortic aneurysm, endografts are currently deployed in the thoracic aorta to treat pathologies without open surgery. However, the thoracic aorta has a singular shapedue to thepresenceof the aortic arch,which can alter thewell positioning, anchorage and thus efficiency of the endograft. A three-dimensional (3D) assessment of thoracic aorta morphometry in function of developed pathology could help clinicians in their surgical choice concerning the appropriate therapeutic procedure and endograft deployment position. The aim of the study was, therefore, to analyse thoracic aorta from several pathological patients before and after endograft deployment, to assess pathological influence on geometry and best endograft positioning.