Mild Acceleration Research Articles

Fetal Diagnosis of Supravalvular Aortic Stenosis and Pulmonary Stenosis in a Family with Non-Syndromic Elastin Mutation.

Supravalvular aortic stenosis (SVAS) has been well described in Williams-Beuren Syndrome and non-syndromic elastin (ELN) mutations. Non-syndromic ELN mutations are inherited in an autosomal dominant pattern with incomplete penetrance and variable expressivity. ELN haploinsufficiency leads to progressive arteriopathy, typically affecting the aortic sinotubular junction. Multi-level pulmonary stenosis has also been reported and biventricular obstruction may portend a worse prognosis. Fetal presentation of ELN mutation with SVAS has not been previously reported in the literature. We present a case of fetal diagnosis of SVAS and multi-level pulmonary stenosis in a family with a known pathogenic ELN mutation (Exon 6, c.278del [p.Pro93Leufs*29]). On the fetus' initial fetal echo, there was only mild flow acceleration through the aortic outflow tract, however, she went on to develop progressive bilateral obstruction. In the early post-natal period, the child was clinically asymptomatic and showed similar mild SVAS and mild valvar and supravalvular pulmonary stenosis. Our case highlights the need for serial monitoring of fetuses with suspected or confirmed ELN arteriopathy.

An Enabling Trajectory Planning Scheme for Lane Change Collision Avoidance on Highways

This paper presents a hierarchical three-layer trajectory planning framework to realize real-time collision avoidance under complex driving conditions. This is mainly ascribed to the generation of a collision-free trajectory cluster based on the speed and the path re-planning. The upper-layer controller is to generate a reference quintic polynomial trajectory based on the Sequential Quadratic Programming by assuming mild speed and acceleration variations of the surrounding vehicles. The waypoints and time stamps can be obtained via the reference trajectory. When the assumption is invalid under complex driving conditions, the middle-layer controller would generate a Quadratic Programming-based trajectory cluster to assign different time stamps to each waypoint through time-based sampling methods. The lower-layer controller would be triggered to create a new feasible trajectory based on the path sampling if the collision avoidance requirements are not satisfied. The host vehicle will return to its original lane if no feasible time window is available to perform a lane change maneuver under the vehicle kinematics and lane change time/displacement constraints. The effectiveness of the proposed scheme is verified under various scenarios through comprehensive simulations.

Abstract 15146: A Flying Saucer- Asymptomatic Migration of an Atrial Septal Defect Occluder Device to the Aortic Arch - No Good Deed Goes Unpunished!

Introduction: Though safe, the transcatheter closure with an atrial septal defect for secundum atrial septal defect (ASD) is associated with complications, such as device dislodgement. Case report: A 51-year-old female with a complex fenestrated secundum ASD (16mm superior defect and 14mm inferior defect with insufficient aortic rim) with hemodynamically significant shunt causing right heart dysfunction underwent placement of two atrial septal defect occluder devices (Amplatzer). While there was no shunting noted on immediate post-procedure transthoracic echocardiogram (TTE), a follow-up TTE after a year showed residual left to right shunting across the ASD. Transesophageal echocardiogram (TEE) showed a single occluder device (inferior) in place and a second device (superior) lodged in the distal aortic arch at the level of the left common carotid and left subclavian artery with mild local flow acceleration (aortic velocity 2.6 ms/s) and no superimposed device thrombus. Her only complaint was recurrent headaches, which pre-dated the procedure and were attributed to ocular migraine by her neurologist. The patient underwent a transcatheter procedure to attempt the retrieval of the dislodged device. The proximal end of the device was found adherent to the aortic wall. Aortogram revealed excellent flow around the device. The procedure was aborted due to the risk of dissection. Since the device did not cause any adverse effects and would likely continue to endothelialization. Conclusion: Atrial septal occluder device dislodgement can occur several months after implantation. Careful monitoring is required particularly when the ASD rim is insufficient. In cases of migration and adherence to the aortic wall without hemodynamic consequences, the device can likely be safely left in place to endothelialize. Despite a faster recovery with percutaneous procedures, a surgical approach should be considered in younger patients to avoid such complications.

S2653 Recurrent Bleeding Gastrointestinal Angioectasias and Acquired Von Willebrand Deficiency (Heyde’s Syndrome) Developing in the Setting of Mild Hypertrophic Obstructive Cardiomyopathy

Introduction: Heyde’s Syndrome is classically described as a triad of gastrointestinal arteriovenous malformations, aortic stenosis (AS), and acquired von Willebrand syndrome (aVWS). Acknowledged as under-diagnosed, the syndrome is frequently missed even in the presence of classically associated moderate-to-severe AS. Perhaps compounding diagnostic difficulty are more recent reports of alternative forms of structural heart disease, including hypertrophic obstructive cardiomyopathy (HOCM), that, although rarer, are capable of producing the syndrome as well. Case Description/Methods: 68-year-old woman with mild hypertrophic obstructive cardiomyopathy that resulted in 5 years of gastrointestinal bleeding episodes before the discovery of bleeding duodenal angioectasias. Initially diagnosed with “HOCM morphology” without evidence of dynamic obstruction on stress echocardiogram, bleeding episodes began to develop shortly after routine annual surveillance echo demonstrated a progression to mildly increased left ventricular outflow tract (LVOT) gradient. Cardiac magnetic resonance imaging (MRI) not only confirmed mild primary HOCM without secondary cause of hypertrophy, but also demonstrated mild flow acceleration across the LVOT, consistent with the hypothesized hemodynamic turbulence and sheer-stress believed to be the mechanism behind acquired von Willebrand deficiency. Within a year, gastrointestinal bleeding would ensue, beginning a prolonged clinical course with multiple hospitalizations for symptomatic anemia requiring transfusions. The eventual discovery of angioectasias prompted von Willebrand Factor analysis which found evidence of acquired deficiency and confirmed the diagnosis of Heyde Syndrome. The patient was subsequently referred for evaluation and definitive treatment of her HOCM with septal ablation, an intervention with which case series have demonstrated the potential for reversal of von Willebrand Factor deficiency and bleeding episodes. Discussion: Often a delayed diagnosis owing to the seemingly disparate constellation of findings in Heyde’s, this particular case additionally highlights that even more mild states of structural heart disease can provoke the syndrome outside of previously reported severe structural disease. Diagnostic suspicion must remain high and von Willebrand factor analysis considered in the combined presence of GI bleed and mild cardiomyopathy and valvulopathy.

Transvenous embolization of moderate to large patent ductus arteriosus in dogs using the Amplatzer vascular plug II.

BackgroundCatheter‐based occlusion of patent ductus arteriosus (PDA) can be performed using different devices. Transvenous embolization using the Amplatzer vascular plug II (AVP‐II) has been studied in humans, but it has not been described in dogs.ObjectiveEvaluate the feasibility and success of transvenous embolization of PDA using the AVP‐II in dogs.AnimalsNineteen client‐owned dogs with left‐to‐right shunting PDA, with minimal ductal diameter >2.5 mm.MethodsProspective observational study using AVP‐II with transvenous access for PDA closure in dogs.ResultsAngiography showed a conical ductus with a long (n = 17) or short (n = 2) ampulla. The minimal diameter of the duct was 4.34 ± 1.11 mm, and the maximal diameter of the ampulla was 13.18 ± 3.47 mm. Technical success was achieved in 18 of the 19 (94.7%) patients after the first intervention and in all 19 (100%) patients after the second intervention. Postrelease angiography documented complete occlusion of the PDA in 10 of 19 (52.6%) dogs. Mild flow acceleration or stenosis of the left pulmonary artery was found in 6 and 1 of the 17 analyzed cases, respectively, by Doppler examination. The closure rate 24 hours after intervention was 94.7% (18/19). The remaining dog had a moderate residual shunt, and delayed complete closure after 3 months led to a 100% closure rate.Conclusion and Clinical ImportanceThe AVP‐II is a safe and effective device for transvenous embolization in dogs with moderate to large PDA.

Missed pulmonary artery sarcoma requiring radical excision and pneumonectomy.

A 64-year-old male patient was referred with 3-month history of progressive shortness of breath and nonexertional chest pain radiating to the back. The initial diagnosis on computed tomography (CT) scan was pulmonary embolus (Figure 1, A-C) and managed with anticoagulation therapy for 6 months. Follow-up CT demonstrated growth of the mass, prompting referral to thoracic surgery for further evaluation. A transthoracic echocardiogram demonstrated mild flow acceleration across the pulmonary valve and estimated pulmonary pressures of 55 to 60 mm Hg.

A MISSED PULMONARY ARTERY SARCOMA REQUIRING RADICAL EXCISION AND PNEUMONECTOMY: SURGICAL TECHNIQUE

<h3>BACKGROUND</h3> A 64-year-old previously well male patient was referred with a 3-month history of progressive shortness of breath (New York Heart Association class III) and non-exertional chest pain radiating to the back. TA transthoracic echocardiogram (TTE) demonstrated mild flow acceleration across the pulmonary valve, without insufficiency and estimated pulmonary pressures of 55 - 60 mmHg. Repeat CT scan identified an approximately 6 cm mass completely filling the right pulmonary artery (RPA) to the hilum and extending down the main pulmonary artery (MPA), potentially involving the pulmonary valve. The left pulmonary artery (LPA) appeared mostly spared. Multidisciplinary oncological team evaluation suggested concerns for pulmonary artery sarcoma prompting consideration for urgent radical excision with homograft reconstruction and right pneumonectomy. <h3>METHODS AND RESULTS</h3> Upon discovery of bilateral PAS in our patient, we decided intraoperatively to continue with a complete radical resection and pneumonectomy, keeping with the goal of complete curative excision. This required extensive planning for surgery including ensuring homograft availability for reconstruction of the pulmonary root and its branches. Cardioplegic arrest was utilized to allow aortic transection to provide optimal exposure posterior to the aorta to determine tumor extension. Given only partial extension into the LPA, we prioritized good margins distally towards the left lung, and used an additional pulmonary allograft for reconstruction. Complete obstruction of the RPA and tumor extension into the right lung necessitated a right pneumonectomy. Pathology confirmed intimal sarcoma with negative margins, and confirmed tumor spread into the right lung parenchyma. At 6 months follow-up, this patient is doing well with no signs of tumour recurrence. Repeat CT demonstrates a patent and functional reconstructed MPA and LPA. <h3>CONCLUSION</h3> Though this technique requires meticulous planning and surgical expertise, it offers a reasonable alternative to conventional management with greater survival benefit. The hope is this approach can build on past literature and lead to longer survival post-operation in patients diagnosed with this rare but deadly disease.

Indirect Measurements of Acceleration Atelectasis and the Role of Inspired Oxygen Concentrations.

BACKGROUND: A growing number of symptom reports suggestive of acceleration atelectasis in fast jet aircrew have raised the question as to whether traditional guidelines on inspired gas composition remain valid. The aim of this study was to assess the effects of inspired O₂ concentration on the development of acceleration atelectasis when wearing modern anti-G garments. METHODS: There were 14 nonaircrew subjects who completed 5 centrifuge exposures to +5 Gz lasting 90 s. During exposures subjects breathed a gas mixture containing 21, 35, 45, 60, or 75% O₂. To assess the extent of atelectasis post-Gz, forced inspiratory vital capacity (FIVC), regional FIVC (EITFIVC), shunt, respiratory resistance, reactance, and compliance and peripheral O₂ saturation during a hypoxic exposure were measured. RESULTS: Compared with baseline, FIVC was not statistically significantly altered. EITFIVC was 14.4% lower after the 75% O₂ exposure only with a greater symptom reporting with higher FIO₂ in some individuals. A significantly greater shunt (3>6%) followed the 60 and 75% O₂ exposures. O₂ concentration during Gz had no effect on respiratory resistance, reactance, compliance, or hypoxemia. DISCUSSION: There is evidence of mild acceleration atelectasis present when breathing 60% O₂, particularly in susceptible individuals, with 75% O₂ causing more obvious physiological compromise. An inspired oxygen concentration of <60% will prevent the majority of individuals from developing acceleration atelectasis. Pollock RD, Gates SD, Radcliffe JJ, Stevenson AT. Indirect measurements of acceleration atelectasis and the role of inspired oxygen concentrations. Aerosp Med Hum Perform. 2021; 92(10):780785.

Natural oscillatory modes of 3D deformation of the human brain in vivo

Natural modes and frequencies of three-dimensional (3D) deformation of the human brain were identified from in vivo tagged magnetic resonance images (MRI) acquired dynamically during transient mild acceleration of the head. Twenty 3D strain fields, estimated from tagged MRI image volumes in 19 adult subjects, were analyzed using dynamic mode decomposition (DMD). These strain fields represented dynamic, 3D brain deformations during constrained head accelerations, either involving rotation about the vertical axis of the neck or neck extension. DMD results reveal fundamental oscillatory modes of deformation at damped frequencies near 7 Hz (in neck rotation) and 11 Hz (in neck extension). Modes at these frequencies were found consistently among all subjects. These characteristic features of 3D human brain deformation are important for understanding the response of the brain in head impacts and provide valuable quantitative criteria for the evaluation and use of computer models of brain mechanics.

Impact of statin intake on malignant hyperthermia: an in vitro and in vivo swine study

BackgroundStatin intake is associated with muscular side effects, among which the unmasking of latent myopathies and of malignant hyperthermia (MH) susceptibility have been reported. These findings, together with experimental data in small animals, prompt speculation that statin therapy may compromise the performance of skeletal muscle during diagnostic in vitro contracture tests (IVCT). In addition, statins might reduce triggering thresholds in susceptible individuals (MHS), or exacerbate MH progression. We sought to obtain empirical data to address these questions.MethodsWe compared the responses of 3 different muscles from untreated or simvastatin treated MHS and non-susceptible (MHN) pigs. MHS animals were also invasively monitored for signs of impending MH during sevoflurane anesthesia.ResultsMuscles from statin treated MHS pigs responded with enhanced in vitro contractures to halothane, while responses to caffeine were unaltered by the treatment. Neither agent elicited contractures in muscles from statin treated MHN pigs. In vivo, end- tide pCO2, hemodynamic evolution, plasma pH, potassium and lactate concentrations consistently pointed to mild acceleration of MH development in statin-treated pigs, whereas masseter spasm and rigor faded compared to untreated MHS animals.ConclusionsThe diagnostic sensitivity and specificity of the IVCT remains unchanged by a short-term simvastatin treatment in MHS swine. Evidence of modest enhancement in cardiovascular and metabolic signs of MH, as well as masked pathognomonic muscle rigor observed under simvastatin therapy suggest a potentially misleading influence on the clinical presentation of MH. The findings deserve further study to include other statins and therapeutic regimes.

Appropriate Timing of Gestational Diabetes Mellitus Diagnosis in Medium- and Low-Risk Women: Effectiveness of the Italian NHS Recommendations in Preventing Fetal Macrosomia

Background Screening strategies for gestational diabetes mellitus (GDM) earlier than 24-28 weeks of gestation should be considered to prevent adverse pregnancy outcomes. Nonetheless, there is uncertainty about which women would benefit most from early screening and which screening strategies should be offered to women with GDM. The Italian National Healthcare Service (NHS) recommendations on selective screening for GDM at 16-18 weeks of gestation are effective in preventing fetal macrosomia in high-risk (HR) women, but the appropriateness of timing and effectiveness of these recommendations in medium- (MR) and low-risk (LR) women are still controversial. Patients and Methods. We retrospectively enrolled 769 consecutive singleton pregnant women who underwent both anomaly scan at 19-21 weeks of gestation and screening for GDM at 16-18 and/or 24-28 weeks of gestation, in agreement with the NHS recommendations and risk stratification criteria. Comparison of maternal characteristics, fetal biometric parameters at anomaly scan (head circumference (HC), biparietal diameter (BPD), abdominal circumference (AC), femur length (FL), estimated fetal weight (EFW)), and neonatal birth weight (BW) percentile among risk groups was examined. Results 219 (28.5%) women were diagnosed with GDM, while 550 (71.5%) were normal glucose-tolerant women. Out of 164 HR women, only 62 (37.8%) underwent the recommended early screening for GDM at 16-18 weeks of gestation. AC and EFW percentiles, as well as neonates' BW percentiles, were significantly higher in HR women diagnosed with GDM at 24-28 weeks of gestation with respect to normal glucose-tolerant women, as well as MR and LR women who tested positive for GDM. Comparative analysis between MR and LR women with GDM and women with normal glucose tolerance revealed significant differences in both AC and EFW percentiles (P < 0.05), while there was no significant difference in neonatal BW percentiles. Conclusion In MR and LR women with GDM, a mild acceleration of fetal growth can be detected at the time of anomaly scan. However, in these at-risk categories, the NHS recommendations for screening and treatment of GDM at 24-28 weeks of gestation are still effective in normalizing BW and preventing fetal macrosomia, thus supporting a risk factor-based selective screening program for GDM.

Incidence and fate of device-related left pulmonary artery stenosis and aortic coarctation in small infants undergoing transcatheter patent ductus arteriosus closure.

To evaluate short- and middle-term outcomes after transcatheter patent ductus arteriosus (TC-PDA) closure in small infants, specifically device-related left pulmonary artery (LPA) stenosis and aortic coarctation, risk factors, and changes over time. Recent studies have demonstrated successful transcatheter PDA (TC-PDA) closure in small infants. LPA stenosis and aortic coarctation have been seen after TC-PDA, but it is not clear whether device-related LPA/aortic obstruction persists. A single-center retrospective study of infants ≤4 kg who underwent TC-PDA closure from February 1, 2007 to September 1, 2018 was performed, evaluating the incidence and risk factors for LPA stenosis and coarctation. Forty-four patients underwent successful TC-PDA with Amplatzer Vascular Plug II (AVPII; n = 30), Amplatzer Duct Occluder II-Additional Sizes (n = 10), Amplatzer Duct Occluder I (n = 3), and coil-filled AVPI (n = 1) devices, all via an antegrade approach. Median birthweight and procedural weight were 890 g (range: 490-3,250) and 2.8 kg (range: 1.2-4.0), respectively. Median follow-up was 0.7 years (range: 2 days-7 years). Thirty-eight patients had post-procedure echocardiograms assessing LPA/aortic obstruction. Of those, 17 had LPA flow acceleration/stenosis (≥1.5 m/s), which improved or resolved in all patients with available follow-up; 3 developed mild coarctation (>2 m/s), which improved in the two with more than short-term follow-up; 4 developed mild flow acceleration (1.5-2 m/s) in the descending aorta, which resolved in three and increased in one (2.4 m/s). Flow acceleration in the LPA was associated with younger procedural age, larger PDA minimal diameter, and placement of a device other than the AVPII. There was no device-related mortality or need for reintervention. TC-PDA in small infants is effective, without significant complications. Device-related LPA/aortic obstruction can improve with time/growth.

Statistical Characterization of Human Brain Deformation During Mild Angular Acceleration Measured In Vivo by Tagged Magnetic Resonance Imaging.

Understanding of in vivo brain biomechanical behavior is critical in the study of traumatic brain injury (TBI) mechanisms and prevention. Using tagged magnetic resonance imaging, we measured spatiotemporal brain deformations in 34 healthy human volunteers under mild angular accelerations of the head. Two-dimensional (2D) Lagrangian strains were examined throughout the brain in each subject. Strain metrics peaked shortly after contact with a padded stop, corresponding to the inertial response of the brain after head deceleration. Maximum shear strain of at least 3% was experienced at peak deformation by an area fraction (median±standard error) of 23.5±1.8% of cortical gray matter, 15.9±1.4% of white matter, and 4.0±1.5% of deep gray matter. Cortical gray matter strains were greater in the temporal cortex on the side of the initial contact with the padded stop and also in the contralateral temporal, frontal, and parietal cortex. These tissue-level deformations from a population of healthy volunteers provide the first in vivo measurements of full-volume brain deformation in response to known kinematics. Although strains differed in different tissue type and cortical lobes, no significant differences between male and female head accelerations or strain metrics were found. These cumulative results highlight important kinematic features of the brain's mechanical response and can be used to facilitate the evaluation of computational simulations of TBI.

Nonlinear evolutions of large amplitude oblique whistler waves

This paper investigates nonlinear evolutions of large amplitude oblique whistler waves (LOWWs) and the interaction with electrons using one-dimensional electromagnetic kinetic simulations. The present research is motivated by recent studies about the nonlinear phenomena of LOWWs. When the propagation angle is not close to the resonance cone angle, the trapping of electrons in the electric potential of LOWWs leads to a moderate damping and a mild acceleration of the electrons via the O'Neil-type damping. In contrast, when the propagation angle of LOWWs is close to the resonance cone angle, the LOWWs undergo a heavy damping accompanied by the stochastic thermalization of the electrons, especially in the perpendicular direction. It is found that the stochastic parameter S, defined by S=16k∥2(eme)Φ0 |J0(k⊥ρ)|ωce2, is a crucial factor determining the damping process. This result demonstrates the importance of self-consistent electron kinetic effects, which are not included in the previous single-particle or fluid approach. The implications of the present findings are discussed.

Transient behaviors of wall turbulence in temporally accelerating channel flows

The effects of mean flow acceleration on near-wall turbulent structures were investigated by performing direct numerical simulations of transient turbulent flows in a channel. The simulations were initiated with a fully developed turbulent channel flow and then temporal accelerations were applied. During the acceleration, almost linearly increasing excursions of the flow rate were imposed between the steady initial and final values. The initial Reynolds number (based on the friction velocity) was fixed to Reτ,i=180, and four different final Reynolds numbers (Reτ,f= 250, 300, 350, and 395) were selected to show the effects of the Reynolds number ratio (Reτ,f/Reτ,i) on the transient channel flows. To elucidate the effects of the flow acceleration rates on the near-wall turbulence, a wide range of acceleration durations has been examined. Various turbulent statistics and instantaneous flow fields revealed that the rapid increase in the flow rate invokes bypass-transition-like phenomena in the transient flow. In contrast, the flow evolves progressively and the transition does not occur clearly for the mild flow acceleration. When the increase in the Reynolds number is small during the acceleration, distinct bypass-like transition phenomena do not appear in the transient flows, regardless of the acceleration rate. The present study proposed new criteria based on the impulse of the acceleration in order to explain the transition to the new turbulence in the transient channel flow. The bypass-like transition is primarily due to the larger contribution of the impulse to the increase in the flow rate compared with that in viscous friction.

Test Suite for Image-Based Motion Estimation of the Brain and Tongue.

Noninvasive analysis of motion has important uses as qualitative markers for organ function and to validate biomechanical computer simulations relative to experimental observations. Tagged MRI is considered the gold standard for noninvasive tissue motion estimation in the heart, and this has inspired multiple studies focusing on other organs, including the brain under mild acceleration and the tongue during speech. As with other motion estimation approaches, using tagged MRI to measure 3D motion includes several preprocessing steps that affect the quality and accuracy of estimation. Benchmarks, or test suites, are datasets of known geometries and displacements that act as tools to tune tracking parameters or to compare different motion estimation approaches. Because motion estimation was originally developed to study the heart, existing test suites focus on cardiac motion. However, many fundamental differences exist between the heart and other organs, such that parameter tuning (or other optimization) with respect to a cardiac database may not be appropriate. Therefore, the objective of this research was to design and construct motion benchmarks by adopting an "image synthesis" test suite to study brain deformation due to mild rotational accelerations, and a benchmark to model motion of the tongue during speech. To obtain a realistic representation of mechanical behavior, kinematics were obtained from finite-element (FE) models. These results were combined with an approximation of the acquisition process of tagged MRI (including tag generation, slice thickness, and inconsistent motion repetition). To demonstrate an application of the presented methodology, the effect of motion inconsistency on synthetic measurements of head-brain rotation and deformation was evaluated. The results indicated that acquisition inconsistency is roughly proportional to head rotation estimation error. Furthermore, when evaluating non-rigid deformation, the results suggest that inconsistent motion can yield "ghost" shear strains, which are a function of slice acquisition viability as opposed to a true physical deformation.

Early clinical experience with the new Amplatzer Ductal Occluder II for closure of the Persistent Arterial Duct (PDA)

Introduction: Transcatheter PDAclosure has gained acceptance over surgery because of its cosmetic benefits, shorter hospital stay and absence of pain associated with a thoracotomy. The Amplatzer Ductal Occluder II (ADOII) device provides a solution for the closure of small to moderate-sizedPDAs Objective: To describe early single-centre clinical experience withADOII. Methods: Children with a haemodynamically significant patent ductus arteriosus (PDA) who underwent percutaneous trans-pulmonary closure with Amplatzer Ductal Occluder II (ADO II) were included. Data was collected from computer based patient records. Results: Trans-pulmonary PDAclosures usingADOII were undertaken in 65 children (46 females) with a mean age of 2years 3 months (range 5 months to 14 years) and a mean weight of 9.6kg (range 4.2-25kg). Complete occlusion was noted pre-discharge in 64 (98.4%) patients. One (1.6%) had residual shunting after deployment followed by embolization to the left pulmonary artery on the third day of the procedure. Of the 65 children, five (7.7%) had mild flow acceleration in the left pulmonary artery and another one (1.6%) had mild aortic flow obstruction following the procedure. At 7 and 30 days, echocardiography confirmed complete ductal occlusion without need for further intervention in all 64 (98.4%) successful cases. Conclusions: ADO II is highly effective in rapid occlusion of morphologically varied small to moderate-sized PDAs.

A fast joint seismic data reconstruction by sparsity‐promoting inversion

ABSTRACTSeismic field data are often irregularly or coarsely sampled in space due to acquisition limits. However, complete and regular data need to be acquired in most conventional seismic processing and imaging algorithms. We have developed a fast joint curvelet‐domain seismic data reconstruction method by sparsity‐promoting inversion based on compressive sensing. We have made an attempt to seek a sparse representation of incomplete seismic data by curvelet coefficients and solve sparsity‐promoting problems through an iterative thresholding process to reconstruct the missing data. In conventional iterative thresholding algorithms, the updated reconstruction result of each iteration is obtained by adding the gradient to the previous result and thresholding it. The algorithm is stable and accurate but always requires sufficient iterations. The linearised Bregman method can accelerate the convergence by replacing the previous result with that before thresholding, thus promoting the effective coefficients added to the result. The method is faster than conventional one, but it can cause artefacts near the missing traces while reconstructing small‐amplitude coefficients because some coefficients in the unthresholded results wrongly represent the residual of the data. The key process in the joint curvelet‐domain reconstruction method is that we use both the previous results of the conventional method and the linearised Bregman method to stabilise the reconstruction quality and accelerate the recovery for a while. The acceleration rate is controlled through weighting to adjust the contribution of the acceleration term and the stable term. A fierce acceleration could be performed for the recovery of comparatively small gaps, whereas a mild acceleration is more appropriate when the incomplete data has a large gap of high‐amplitude events. Finally, we carry out a fast and stable recovery using the trade‐off algorithm. Synthetic and field data tests verified that the joint curvelet‐domain reconstruction method can effectively and quickly reconstruct seismic data with missing traces.

Effect of a mesh on boundary layer transitions induced by free-stream turbulence and an isolated roughness element

Streamwise streaks, their lift-up and streak instability are integral to the bypass transition process. An experimental study has been carried out to find the effect of a mesh placed normal to the flow and at different wall-normal locations in the late stages of two transitional flows induced by free-stream turbulence (FST) and an isolated roughness element. The mesh causes an approximately 30 % reduction in the free-stream velocity, and mild acceleration, irrespective of its wall-normal location. Interestingly, when located near the wall, the mesh suppresses several transitional events leading to transition delay over a large downstream distance. The transition delay is found to be mainly caused by suppression of the lift-up of the high-shear layer and its distortion, along with modification of the spanwise streaky structure to an orderly one. However, with the mesh well away from the wall, the lifted-up shear layer remains largely unaffected, and the downstream boundary layer velocity profile develops an overshoot which is found to follow a plane mixing layer type profile up to the free stream. Reynolds stresses, and the size and strength of vortices increase in this mixing layer region. This high-intensity disturbance can possibly enhance transition of the accelerated flow far downstream, although a reduction in streamwise turbulence intensity occurs over a short distance downstream of the mesh. However, the shape of the large-scale streamwise structure in the wall-normal plane is found to be more or less the same as that without the mesh.

Mid-Term Follow-Up after Arterial Switch Operation for Complete Transposition of the Great Arteries

Purpose : Transposition of the Great Arteries has to be surgically corrected by an arterial switch operation. This complex surgical procedure has the potential for significant short- and long-term complications like dilation of the neo-aortic root, coronary and pulmonary artery (PA) stenosis. The aim was to determine a suitable follow-up algorithm for mid-term follow-up. Material and Methods : 26 patients (mean age 10±2 years) were examined using echocardiography, ECG-gated Computed Tomography Angiography (CTA) and functional Magnetic Resonance Imaging (MRI) with flow, cine and pulmonary perfusion measurements. Results : CTA was capable to visualize coronary arteries in all cases. Coronary stenosis did not occur. Echocardiography failed to visualize the coronary arteries in 81%. CTA revealed moderate PA stenosis (25-50% lumen reduction) in 41% and severe stenosis (>50%) in10%. Visualization of pulmonary arteries was possible by echocardiography in only 45%. Correlation between MR-pulmonary perfusion abnormalities and PA stenosis were not present. Doppler-echocardiography showed mild flow acceleration in the main PA (mean pressure gradient 34mmHg) in 4 patients, while MRI found an increased velocity in 9 patients. 10 patients had neo-aortic root dilatation detected with CTA. On echocardiography 8 patients had mild, 4 had moderate aortic valve insufficiency. On MRI amount of aortic valve insufficiency was too small to be quantified. Conclusion : Branch stenosis of the PA was the leading complication 10 years after surgery, coronary stenosis did not occur. Value of Echocardiography is minor in the visualization of coronary arteries and PA morphology and it is recommended only for the assessment of cardiac and valvular function. Additionally, CTA is method of choice for visualization of coronary arteries and PA morphology. In this study the value of MRI for assessment of the complete morphology was limited, but improves with technical advance.