Search

Background: Epidemiological studies reported that preterm infants have increased arterial systemic blood pressure in adulthood. We have recently shown in an animal model that premature vascular aging could be involved in this process.Aim: To assess biophysical properties (arterial stiffness) of the aorta as early signs of a vascular aging process in young adult women born extremely preterm.Methods: We studied 4 women (aged 24±1 years) born extremely preterm (26.1±0.5 weeks, 803±58 grams) in the absence of any significant medical or psychiatric co-morbidity. Subjects were compared to 6 control women born at term (40.6±0.8 weeks, 32518±139 grams) matched for age. The aortic diameters, the pulse wave transit time around the aortic arch and the ascending aortic peak flow were measured with echo-Doppler and the blood pressure recorded. Pulse wave velocity, aortic input impedance (Zi), characteristic impedance (Zc), arterial pressure-strain elastic modulus (Ep), and arterial wall stiffness index (βSI) were calculated.Results: Preterm women had slightly but not significantly increased arterial systolic blood pressure compared to young women born term (111±6 vs. 104±2 mmHg, p=0.23). Diastolic and mean arterial blood pressure were similar (62±4 vs. 61±3, p=0.84 and 77±4 vs. 75±3 mmHg, p=0.73 respectively). Pulse wave velocity did not differ between groups (3.6±0.6 vs. 3.2±0.2 m/sec, p=0.53). βSI and Ep, direct indices of central arterial rigidity, were not significantly different between preterm women compared to controls (4.9±2.1 vs. 3.7±0.4, p=0.46 and 58±24 vs. 42±4 kPa, p=0.38 respectively). Zc and Zi, indices of the resistance to ejection to blood flow, were increased compared to controls (134±21 vs. 105±9, p=0.18 and 185±8 vs. 152±10, p<0.05 dynes. sec. cm-5, respectively).Conclusions: This first series of results suggest that women who were born very preterm present indices of arterial rigidity compared to term controls. This alteration of the vascular tree could be a patho-physiological mechanism linking prematurity to adult cardiovascular diseases. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to evaluate whether changes of uterine arteries and aortic isthmus Doppler blood flow recordings could enhance the prediction of necrotizing enterocolitis. Study Design: Doppler characteristics of the uterine artery, umbilical and middle cerebral arteries, ductus venosus, and aortic isthmus were reviewed in 123 growth-restricted fetuses who were then divided into 2 groups: with and without necrotizing enterocolitis. Results: Twelve of 123 newborn infants (9%) expressed necrotizing enterocolitis. This group showed significant association between necrotizing enterocolitis and bilateral notching on the uterine artery (83.3% vs 29.7%; P < .001), uterine artery mean resistance index (83.3% vs 36.9%; P < .002), aortic isthmus diastolic blood flow velocity integrals (Z score: –7.32 vs –3.99; P = .028), and absent or negative “a” wave on the ductus venosus (17% vs 1.8%; P = .021). With the use of logistic regression, uterine bilateral notching could predict necrotizing enterocolitis with a sensitivity of 83.3% and a specificity of 70.3%. Conclusion: More than any other variable, uterine bilateral notching should be recognized as a strong risk factor for necrotizing enterocolitis. [ABSTRACT FROM AUTHOR]

Introduction: Left ventricular outflow tract obstruction (LVOTO) is a wide spectrum of congenital heart defects ranging from bicuspid aortic valve to hypoplastic left heart syndrome. Increasing knowledge suggests a strong contribution of genetic factors in this disease spectrum. Methods: We have recruited a large cohort of multiplex families with LVOTO. All individuals gave informed consent and underwent physical exam, ECG and echocardiography. We have chosen 45 highly informative families and 23 trios for analysis of linkage and structural genomic variation using high-density genotyping (total cohort n = 450, affected = 217). To confidently call copy number variants, a phenotyped control cohort with 1900 members was used. Results: In the 68 families analyzed to date, only one family with a clear Mendelian segregation pattern was identified. This family exhibits a novel X-linked syndrome with atrial septal defects, aortic valve disease, coarctation and atrial fibrillation. Significant linkage to Xq28 could be demonstrated, with a founder effect in a geographically confined area. In the cohort as a whole, significant linkage to chromosome 6q24 was found, defining an 8 Mb critical interval devoid of any obvious biological candidates and without any founder haplotypes. The analysis of copy number variants reveals 33 candidate loci in a highly complex pattern of inherited and de novo variants, 2/3 of which are gains. Conclusions: We provide a comprehensive high-density scan of LVOTO and identify linkage to two novel candidate loci in the French-Canadian population. Detailed haplotype analyses show conservation in a subset of families. Several layers of genetic factors most likely co-exist within this cohort, with structural genomic variation explaining the majority of phenotypic variability. These results pave the way towards a better definition of the causal genes and gene-gene interactions in LVOTO. [ABSTRACT FROM AUTHOR]

The aim of this paper is to improve the position accuracy of a six degree of freedom medical robot. The improvement in accuracy is achieved without the use of any external measurement device. Instead, this work presents a novel calibration approach based on using an embedded force-torque sensor to identify the robot's kinematic parameters and thereby enhance the positioning accuracy. A simulation study demonstrated that our calibration approach is effective, whether or not any measurement noise is present: the position error is improved, inside the robot target workspace, from 12 mm to 0.320 mm, for the maximum values, and from 9 mm to 0.2771 mm, for the mean errors.

Locating and evaluating the length and severity of a stenosis is very important for planning adequate treatment of peripheral arterial disease (PAD). Conventional ultrasound (US) examination cannot provide maps of entire lower limb arteries in 3-D. We propose a prototype 3D-US robotic system with B-mode images, which is nonionizing, noninvasive, and is able to track and reconstruct a continuous segment of the lower limb arterial tree between the groin and the knee. From an initialized cross-sectional view of the vessel, automatic tracking was conducted followed by 3D-US reconstructions evaluated using Hausdorff distance, cross-sectional area, and stenosis severity in comparison with 3-D reconstructions with computed tomography angiography (CTA). A mean Hausdorff distance of 0.97 ± 0.46 mm was found in vitro for 3D-US compared with 3D-CTA vessel representations. To evaluate the stenosis severity in vitro, 3D-US reconstructions gave errors of 3%-6% when compared with designed dimensions of the phantom, which are comparable to 3D-CTA reconstructions, with 4%-13% errors. The in vivo system's feasibility to reconstruct a normal femoral artery segment of a volunteer was also investigated. These results encourage further ergonomic developments to increase the robot's capacity to represent lower limb vessels in the clinical context.

Independent-roller ergometers (IREs) are commonly used to simulate the behaviour of a wheelchair propelled in a straight line. They cannot, however, simulate curvilinear propulsion. To this effect, a motorised wheelchair ergometer could be used, provided that a dynamic model of the wheelchair-user system propelled on straight and curvilinear paths (WSC) is available. In this article, we present such a WSC model, its parameter identification procedure and its prediction error. Ten healthy subjects propelled an instrumented wheelchair through a controlled path. Both IRE and WSC models estimated the rear wheels' velocities based on the users' propulsive moments. On curvilinear paths, the outward wheel shows root mean square (RMS) errors of 13% in an IRE vs 8% in a WSC. The inward wheel shows RMS errors of 21% in an IRE vs 11% in a WSC. Differences between both models are highly significant (p < 0.001). A wheelchair ergometer based on this new WSC model will be more accurate than a roller ergometer when simulating wheelchair propulsion in tight environments, where many turns are necessary.

Due to their mechanical design, current wheelchair ergometers cannot simulate the behaviour of a wheelchair propelled on curvilinear paths. This is because they implement a dynamic model of the Wheelchair-user system propelled on Straight Line only (WSL). In this paper, we present a new dynamic model of the Wheelchair-user propelled on Straight and Curvilinear paths (WSC), along with a characterization method based on measurements recorded on the field. Other than measured geometrical constants and kinetic/kinematic data from instrumented wheels, no information about the dynamic parameters such as the system's mass and its moment of inertia are necessary. The accuracy of the new WSC model was compared with the WSL model. To this end, ten subjects propelled an instrumented wheelchair following straight and curvilinear patterns. The recorded kinetics were fed to both models, and their estimated kinematics were compared to the recorded ones. For the curvilinear patterns, the RMS relative error between the estimated and measured rear wheels velocities over a complete push cycle are lower for the WSC model than for the WSL model. Outward wheel: 7.98% (WSC) vs 12.98% (WSL). Inward wheel: 10.76% (WSC) vs 20.73% (WSL)., (© 2011 IEEE)

3D-ultrasound (US) imaging systems offer many advantages such as convenience, low operative costs and multiple scanning options. Most 3D-US freehand tracking systems are not optimally adapted for the quantification of lower limb arterial stenoses because their performance depends on the scanning length, on ferro-magnetic interferences or because they require a constant line of sight with the US probe. Robotic systems represent a promising alternative since they can control and standardize the 3D-US acquisition process for large scanning distances without requiring a specific line of sight. The performance of a new prototype medical robot, in terms of positioning and inter-target accuracies (i.e., difference between measurements and ground truth values) was evaluated with a lower-limb mimicking phantom throughout the robot workspace. The teach/replay repeatability (i.e., difference between taught and replayed points) was also assessed. A mean positioning accuracy between 0.46 mm and 0.75 mm was found on all scanning zones. The mean inter-target distance accuracy varied between 0.26 mm and 0.61 mm. Teach/replay repeatability below 0.20mm was also obtained. Additionally, a 3D reconstruction of in-vitro stenoses was performed with the robotic US scanner. The quantification error of a 80% area reduction (AR) stenosis was 3.0%, whereas it was -0.9% for a less severe 75% AR stenosis. Altogether, these results suggest that the robot may be of value for the clinical evaluation of lower limb vessels over long and tortuous segments starting from the iliac artery down to the popliteal artery below the knee.