A compliant aortic model for in vitro simulations: Design and manufacturing process.

We design and manufacture a silicone model of the human aorta, able to mimic both the geometrical and the mechanical properties of physiological individuals, with a specific focus on reproducing the compliance. In fact, while the models available in the literature exhibit an unrealistic compliant behavior, though they are detailed from the geometrical viewpoint, here the goal is to provide an accurate compliant tool for in vitro testing the devices that interface with the vascular system. A parametric design of the aortic model is obtained based on the available literature data, and the model is manufactured with a specific silicone mixture using rapid prototyping and molding techniques. The manufactured prototype has been tested by means of computed tomography scans for evaluating the matching of the mechanical properties with the desired ones. Results show a high degree of adherence between the imposed and the measured compliance values for each main aortic section. Thus, our work proves the feasibility of the approach, and the possibility to manufacture compliant models that reproduce the mechanical behavior of the aorta for in vitro studies.

Impact of Thoracic Endovascular Repair on Pulsatile Aortic Strain in Acute Type B Aortic Dissection: Preliminary Results.

BACKGROUND: The impact of thoracic endovascular aortic repair (TEVAR) on pulsatile aortic strain remains undetermined in patients with Type B aortic dissection (TBAD). Therefore, we quantified pulsatile aortic strain in TBAD patients and control subjects. METHODS: We retrospectively analyzed two TBAD patients from our database with cardiac-gated computed tomography angiography imaging available before and after TEVAR and two control subjects (67- and 76-year-old males). Patient 1 (54-year-old female) presented with acute TBAD, and Patient 2 (55-year-old male) had Marfan syndrome and ruptured acute TBAD. Custom-developed software was used to compute aortic length, diameter, and area during the cardiac cycle. Pulsatile strain was calculated as systolic increments of length and circumference divided by corresponding diastolic values. RESULTS: Before TEVAR, pulsatile longitudinal strain of the thoracic aorta was lower in TBAD patients (1.4-1.7%) than in control subjects (2.1-4.5%). After TEVAR, pulsatile longitudinal strain increased proximal to the stent-graft by 65% in the arch of Patient 1 and by 70% in the ascending aorta of Patient 2. Pulsatile circumferential strain was elevated in false lumen patency (4.4-6.2%) compared with thrombosed false lumen (1.4-2.1%) or control subjects (0.9-3.3%). Following TEVAR, circumferential measurements within stented segments were deemed unreliable due to artifacts. CONCLUSIONS: TEVAR led to a considerable increase of pulsatile longitudinal strain proximal to the stent-grafts, and TBAD was associated with longitudinally stiffer aortas, which may be part of the pathophysiology of TEVAR-related complications such as retrograde dissection and aneurysmal dilatation. These preliminary data call for larger prospective studies.

Impact of Thoracic Endovascular Aortic Repair on Pulsatile Circumferential and Longitudinal Strain in Patients With Aneurysm.

PURPOSE: To quantify both pulsatile longitudinal and circumferential aortic strains before and after thoracic endovascular aortic repair (TEVAR), potentially clarifying TEVAR-related complications. METHODS: This retrospective study assessed the impact of TEVAR on pulsatile aortic strains through custom developed software and cardiac-gated computed tomography imaging of 8 thoracic aneurysm patients (mean age 71.0±8.2 years; 6 men) performed before TEVAR and during follow-up (median 0.1 months, interquartile range 0.1-5.8). Lengths of the ascending aorta, the aortic arch, and the descending aorta were measured. Diameters and areas were computed at the sinotubular junction, brachiocephalic trunk, left subclavian artery, and the celiac trunk. Pulsatile longitudinal and circumferential strains were quantified as systolic increments of length and circumference divided by the corresponding diastolic values. RESULTS: Average pulsatile longitudinal strain ranged from 1.4% to 7.1%, was highest in the arch (p<0.001), and increased after TEVAR by 77% in the arch (7.1%±2.5% vs 12.5%±5.1%, p=0.04) and by 69% in the ascending aorta (5.6±2.3% vs 9.4±4.4%, p=0.06). Average pulsatile circumferential strain ranged from 3.6% to 5.0% before TEVAR and did not differ significantly throughout the thoracic aorta; there was a nonsignificant increase after TEVAR at the unstented sinotubular junction (5.0%±1.4% vs 6.3%±1.0%, p=0.18), with a significant increase at the celiac trunk (3.6%±1.8% vs 6.2%±1.8%, p=0.02). Pulsatile circumferential strains within stented segments were deemed unreliable due to image artifacts. CONCLUSION: TEVAR was associated with an increase of pulsatile longitudinal strains (in the arch) and circumferential strains (at the celiac trunk) in unstented aortic segments. These observations suggest increased pulsatile wall stress after TEVAR in segments adjacent to the device, which may contribute to the understanding of stent-graft-related complications such as retrograde dissection, aneurysm formation, and rupture.

Contemporary Management Strategies for Chronic Type B Aortic Dissections: A Systematic Review.

BACKGROUND: Currently, the optimal management strategy for chronic type B aortic dissections (CBAD) is unknown. Therefore, we systematically reviewed the literature to compare results of open surgical repair (OSR), standard thoracic endovascular aortic repair (TEVAR) or branched and fenestrated TEVAR (BEVAR/FEVAR) for CBAD. METHODS: EMBASE and MEDLINE databases were searched for eligible studies between January 2000 and October 2015. Studies describing outcomes of OSR, TEVAR, B/FEVAR, or all, for CBAD patients initially treated with medical therapy, were included. Primary endpoints were early mortality, and one-year and five-year survival. Secondary endpoints included occurrence of complications. Furthermore, a Time until Treatment Equipoise (TUTE) graph was constructed. RESULTS: Thirty-five articles were selected for systematic review. A total of 1081 OSR patients, 1397 TEVAR patients and 61 B/FEVAR patients were identified. Early mortality ranged from 5.6% to 21.0% for OSR, 0.0% to 13.7% for TEVAR, and 0.0% to 9.7% for B/FEVAR. For OSR, one-year and five-year survival ranged 72.0%-92.0% and 53.0%-86.7%, respectively. For TEVAR, one-year survival was 82.9%-100.0% and five-year survival 70.0%-88.9%. For B/FEVAR only one-year survival was available, ranging between 76.4% and 100.0%. Most common postoperative complications included stroke (OSR 0.0%-13.3%, TEVAR 0.0%-11.8%), spinal cord ischemia (OSR 0.0%-16.4%, TEVAR 0.0%-12.5%, B/FEVAR 0.0%-12.9%) and acute renal failure (OSR 0.0%-33.3%, TEVAR 0.0%-34.4%, B/FEVAR 0.0%-3.2%). Most common long-term complications after OSR included aneurysm formation (5.8%-20.0%) and new type A dissection (1.7-2.2%). Early complications after TEVAR included retrograde dissection (0.0%-7.1%), malperfusion (1.3%-9.4%), cardiac complications (0.0%-5.9%) and rupture (0.5%-5.0%). Most common long-term complications after TEVAR were rupture (0.5%-7.1%), endoleaks (0.0%-15.8%) and cardiac complications (5.9%-7.1%). No short-term aortic rupture or malperfusion was observed after B/FEVAR. Long-term complications included malperfusion (6.5%) and endoleaks (0.0%-66.7%). Reintervention rates after OSR, TEVAR and B/FEVAR were 5.8%-29.0%, 4.3%-47.4% and 0.0%-53.3%, respectively. TUTE for OSR was 2.7 years, for TEVAR 9.9 months and for B/FEVAR 10.3 months. CONCLUSION: We found a limited early survival benefit of standard TEVAR over OSR for CBAD. Complication rates after TEVAR are higher, but complications after OSR are usually more serious. Initial experiences with B/FEVAR show its feasibility, but long-term results are needed to compare it to OSR and standard TEVAR. We conclude that optimal treatment of CBAD remains debatable and merits a patient specific decision. TUTE seems a feasible and useful tool to better understand management outcomes of CBAD.

Biomechanical Changes After Thoracic Endovascular Aortic Repair in Type B Dissection: A Systematic Review.

Thoracic endovascular aortic repair (TEVAR) has evolved into an established treatment option for type B aortic dissection (TBAD) since it was first introduced 2 decades ago. Morbidity and mortality have decreased due to the minimally invasive character of TEVAR, with adequate stabilization of the dissection, restoration of true lumen perfusion, and subsequent positive aortic remodeling. However, several studies have reported severe setbacks of this technique. Indeed, little is known about the biomechanical behavior of implanted thoracic stent-grafts and the impact on the vascular system. This study sought to systematically review the performance and behavior of implanted thoracic stent-grafts and related biomechanical aortic changes in TBAD patients in order to update current knowledge and future perspectives.

Evolution in the Management of Aberrant Subclavian Arteries and Related Kommerell Diverticulum.

BACKGROUND: Various options have been described to treat aberrant subclavian arteries and associated Kommerell diverticulum. We describe our experience with the management of this entity over a 15-year period. METHODS: Twenty-two patients underwent repair of aberrant subclavian arteries and associated Kommerell diverticulum. Indications for intervention included a large Kommerell diverticulum (n = 18), dysphagia lusoria (n = 12), rupture (n = 4), type B aortic dissection (n = 4), thoracic aortic aneurysm (n = 2), and coarctation (n = 1). Patients were treated with either open surgery (n = 9) or an endovascular approach (n = 13). For the open surgical patients, hypothermic circulatory arrest (n = 7) or left heart bypass (n = 2) was used. For those patients undergoing an endovascular approach (n = 13), carotid to subclavian arterial bypasses were performed preoperatively in 11 patients and intraoperatively in 2 patients. Bilateral revascularization was more frequently performed with endovascular repair compared with open surgery (69% vs 22%, p = 0.01). RESULTS: Early outcomes included in-hospital mortality (n = 1), stroke (n = 1), and permanent spinal cord ischemia (n = 1) after endovascular approaches, and renal failure requiring dialysis (n = 1) and need for tracheostomy (n = 1) after open repair. The frequency of endovascular repair increased after the commercialization of thoracic endovascular aortic repair in 2005 from 33% to 63%. Four patients developed type I (n = 1) or type II (n = 3) endoleaks, of which 1 required reintervention. Median hospital stay was 7 days (interquartile range 4 to 17). Five-year survival was 81.8%. No late aortic ruptures occurred and 3 patients required late reintervention; 1 after an open and 2 after an endovascular approach. Dysphagia lusoria was relieved in all patients except for 1 in the open repair and 1 in the endovascular group. CONCLUSIONS: Aberrant subclavian arteries and associated Kommerell diverticulum can be treated with acceptable rates of mortality and morbidity. The evolution toward an endovascular approach did not appear to affect late outcomes, suggesting that the choice of treatment should be based on patient-specific anatomy and associated comorbidities.

Propensity adjusted analysis of open and endovascular thoracic aortic repair for chronic type B dissection: a twenty-year evaluation.

BACKGROUND: Optimal treatment of chronic type B aortic dissection (CBAD), whether open (open descending aortic repair, OAR) or endovascular (thoracic endovascular aortic repair, TEVAR), is controversial, suggesting a comparative analysis is warranted. METHODS: One hundred twenty-two of 1,049 patients (1993 to 2013) undergoing descending aortic repair required intervention for CBAD 29.2 ± 34.9 months after the initial acute event and formed the study cohort (mean age 59.7 years). Those with degenerated residual type A dissection were excluded (n = 65). Eighty-eight had extent IIIB CBAD; 11 had intramural hematoma. Indications for surgery included aneurysmal degeneration (n = 105), rupture (n = 8), acute or chronic dissection (n = 8), and extension of dissection (n = 1). Open strategy included descending (n = 71) and thoracoabdominal repair (n = 19), with hypothermic circulatory arrest used in 70 patients. The TEVAR was performed with (n = 2) or without (n = 30) visceral debranching. A treatment strategy propensity score incorporating time since initial acute event, CBAD extent, year of intervention, age, and selected comorbidities was constructed for multivariable analysis. RESULTS: Early outcome included the following: 30-day mortality 4% (n = 5); stroke 2% (n = 2); permanent paraplegia 3% (n = 4); renal failure requiring dialysis 7% (n = 8, 5 temporary and 3 permanent); and tracheostomy 3% (n = 4). Visceral aorta intervention (odds ratio [OR] 3.5, p = 0.026) and maximum aortic diameter (OR 1.1, p = 0.001) but not treatment type (p = 0.64) independently predicted an early composite outcome comprised of these variables. Ten-year survival was 56.2%. Baseline creatinine (hazard ratio [HR] 1.7, p < 0.001) and peripheral vascular disease (HR 2.5, p = 0.021), but not treatment type (p = 0.225) predicted late mortality. Ten-year freedom from aortic rupture or need for reintervention was 78.3%. Treatment efficacy was improved after OAR (3-year freedom 96.7% vs TEVAR 87.5%, p = 0.026), and this was confirmed after Cox regression (TEVAR, HR 4.6, p = 0.046). CONCLUSIONS: Intervention for CBAD can be performed with excellent results, either by an open or endovascular approach. The higher rate of treatment failure after TEVAR warrants modification of current device design or endovascular approach before broad application of this treatment strategy.

Aortic hemodynamics after thoracic endovascular aortic repair, with particular attention to the bird-beak configuration.

PURPOSE: To quantitatively evaluate the impact of thoracic endovascular aortic repair (TEVAR) on aortic hemodynamics, focusing on the implications of a bird-beak configuration. METHODS: Pre- and postoperative CTA images from a patient treated with TEVAR for post-dissecting thoracic aortic aneurysm were used to evaluate the anatomical changes induced by the stent-graft and to generate the computational network essential for computational fluid dynamics (CFD) analysis. These analyses focused on the bird-beak configuration, flow distribution into the supra-aortic branches, and narrowing of the distal descending thoracic aorta. Three different CFD analyses (A: preoperative lumen, B: postoperative lumen, and C: postoperative lumen computed without stenosis) were compared at 3 time points during the cardiac cycle (maximum acceleration of blood flow, systolic peak, and maximum deceleration of blood flow). RESULTS: Postoperatively, disturbance of flow was reduced at the bird-beak location due to boundary conditions and change of geometry after TEVAR. Stent-graft protrusion with partial coverage of the origin of the left subclavian artery produced a disturbance of flow in this vessel. Strong velocity increase and flow disturbance were found at the aortic narrowing in the descending thoracic aorta when comparing B and C, while no effect was seen on aortic arch hemodynamics. CONCLUSION: CFD may help physicians to understand aortic hemodynamic changes after TEVAR, including the change in aortic arch geometry, the effects of a bird-beak configuration, the supra-aortic flow distribution, and the aortic true lumen dynamics. This study is the first step in establishing a computational framework that, when completed with patient-specific data, will allow us to study thoracic aortic pathologies and their endovascular management.

Alternative access techniques with thoracic endovascular aortic repair, open iliac conduit versus endoconduit technique.

BACKGROUND: Iliac artery endoconduits (ECs) have emerged as important alternatives to retroperitoneal open iliac conduits (ROICs) to aid in transfemoral delivery for thoracic endovascular aortic repair (TEVAR). We present, to our knowledge, the first comparative analysis between these alternative approaches. METHODS: All patients undergoing TEVAR with either ROIC (n = 23) or internal EC (n = 16) were identified. The mean age of the cohort was 72.4 ± 11.5 years (82.1% female). Device delivery was accomplished in 100% of cases. The primary outcome was the presence of iliofemoral complications, which was defined as: (1) the inability to successfully deliver the device into the aorta via the ROIC or EC approach; (2) rupture, dissection, or thrombosis of the ipsilateral iliac or femoral artery; and/or (3) retroperitoneal hematoma requiring exploration and evacuation. Secondary outcomes were 30-day mortality and rates of limb loss, claudication, or revascularization. RESULTS: At a median follow-up of 10.1 months, the incidence of iliofemoral complications was less for the EC approach compared with the ROIC technique (12.5% vs 26.1%; P = .301). No patients sustained limb loss. Revascularization was performed in two patients after ROIC. Lower extremity claudication occurred in one patient after EC. Early mortality was seen in one patient who underwent EC. Two-year Kaplan-Meier survival for the entire cohort was 74.4%, and did not differ between groups (ROIC, 78.3% vs EC, 68.8%; P = .350). Two-year Kaplan-Meier freedom from limb loss, claudication, or revascularization did not differ between the two approaches (ROIC, 91.3% vs EC, 93.8%; P = .961). CONCLUSIONS: Results of this early comparative evaluation of alternative access routes for TEVAR suggest that an EC approach is safe, effective, and associated with low rates of early mortality and late iliofemoral complications. In selected patients, the EC may be considered an appropriate delivery route for transfemoral TEVAR.

Predicting aortic enlargement in type B aortic dissection.

Patients with uncomplicated acute type B aortic dissection (ABAD) can generally be treated with conservative medical management. However, these patients may develop aortic enlargement during follow-up, with the risk of rupture. Several predictors have been studied in recent years to identify ABAD patients at high risk of aortic enlargement, who may benefit from early surgical or endovascular intervention. This study reviewed and summarized the current available literature on prognostic variables related to aortic enlargement during follow-up in uncomplicated ABAD patients. It revealed multiple factors affecting aortic expansion including demographic, clinical, pharmacologic and radiologic variables. Such predictors may be used to identify those ABAD patients at higher risk for aortic enlargement who may benefit from closer radiologic surveillance or early endovascular intervention. This approach deserves even more consideration because a significant number of patients develop aneurysmal degeneration along the dissected segments during follow-up, and may lose the opportunity for endovascular treatment if not identified at an early stage.

Importance of dynamic aortic evaluation in planning TEVAR.

Dynamic aortic evaluation in planning thoracic endovascular aortic repair (TEVAR) is important to provide optimal stent graft sizing. Static imaging protocols do not consider normal aortic dynamics and may lead to stent graft to aorta mismatch, causing stent graft related complications, such as type I endoleak and stent graft migration. Dynamic imaging can assist in accurate stent graft selection and sizing preoperatively, and evaluate stent graft performance during follow-up. To create new imaging technologies, integration of knowledge between diverse scientific fields is essential (i.e., engineering, informatics and medicine). Different dynamic imaging modalities, such as electrocardiographic-gated computed tomography angiography (ECG-gated CTA) and four-dimensional phase-contrast MRI (4D PC-MRI), are progressively investigated and implemented into clinical practice as important instruments in preoperative planning for TEVAR. In time, further application of dynamic imaging tools for preoperative screening and follow-up after TEVAR might lead to better outcomes for patients. The advances in dynamic imaging for evaluation of the thoracic aorta using new imaging modalities and their future perspectives are addressed in this manuscript.

Predictors of aortic growth in uncomplicated type B aortic dissection.

BACKGROUND: Patients with uncomplicated acute type B aortic dissection (ABAD) generally can be treated with conservative medical management. However, these patients may develop aortic enlargement during follow-up, with the risk for rupture, which necessitates intervention. Several predictors have been studied in recent years to identify ABAD patients at high risk for aortic enlargement who may benefit from early surgical or endovascular intervention. This study systematically reviewed and summarized the current available literature on prognostic variables related to aortic enlargement during follow-up in uncomplicated ABAD patients. METHODS: Studies were included if they reported predictors of aortic growth in uncomplicated ABAD patients. Studies about type A aortic dissection, aortic aneurysm, intramural hematoma, or ABAD that required acute intervention were excluded. RESULTS: A total of 18 full-text articles were selected. The following predictors of aortic growth in ABAD patients were identified: age <60 years, white race, Marfan syndrome, high fibrinogen-fibrin degradation product level (≥20 µg/mL) at admission, aortic diameter ≥40 mm on initial imaging, proximal descending thoracic aorta false lumen (FL) diameter ≥22 mm, elliptic formation of the true lumen, patent FL, partially thrombosed FL, saccular formation of the FL, presence of one entry tear, large entry tear (≥10 mm) located in the proximal part of the dissection, FL located at the inner aortic curvature, fusiform dilated proximal descending aorta, and areas with ulcer-like projections. Tight heart rate control (<60 beats/min), use of calcium-channel blockers, thrombosed FL, two or more entry tears, FL located at the outer aortic curvature, and circular configuration of the true lumen were associated with negative or limited aortic growth. CONCLUSIONS: Several predictors might be used to identify those ABAD patients at high risk for aortic growth. Although conservative management remains indicated in uncomplicated ABAD, these patients might benefit from closer follow-up or early endovascular intervention.

Biomarkers in TAA-the Holy Grail.

Thoracic aortic aneurysm (TAA) is a silent disease, often discovered at a time point that dramatic complications, as rupture and dissection, occur. For the detection of asymptomatic TAA and prevention of such complications, it is essential to have an adequate screening tool. Until now, routine laboratory blood tests have played only a minor role in the screening, diagnosis, tracking and prediction of the natural history of TAAs. However, the knowledge about biomarkers is rapidly expanding in the cardiovascular field, and there are several potential biomarkers that might be implemented into TAA clinical practice in the near future. The most important and promising markers for TAA will be discussed in this overview.

A prospective assessment of renal oxygenation in children undergoing laparoscopy using near-infrared spectroscopy.

BACKGROUND: This study was designed to determine whether a decrease in renal oxygenation occurs during CO2 pneumoperitoneum in children with normal renal function undergoing laparoscopy. METHODS: Near infrared spectroscopy (NIRS) probes were applied to both the lateral flank (T10-L2) and lateral cerebral area of all patients with normal renal function undergoing a laparoscopic procedure. Information was recorded in 5-s intervals for 15-min before, during, and for 15-min after pneumoperitoneum insufflation and desufflation. Simultaneously, additional hemodynamic parameters (arterial saturation, mean arterial pressure, end tidal CO2, and urine output) were recorded every 5-min. Pneumoperitoneum pressures used were: 0-1 month old, <6 mmHg; 2-12 months old, <8 mmHg; 1-2 years old, <10 mmHg, and 2-8 years old, <12 mmHg. The lowest possible pressure was used to obtain adequate vision. RESULTS: Twenty-nine patients were enrolled in the study. Renal regional oxygen saturation (rSO2) did not decrease significantly between baseline (preinsufflation), insufflation, and desufflation of the pneumoperitoneum (p = 0.343). Meta-analysis of this data demonstrated a pooled weighted difference of -1.4 (-3.5 to 0.54), confirming no significant change. A significant increase in cerebral rSO2 occurred during the insufflation period of the CO2 pneumoperitoneum (p = 0.001). Heart rate (F = 11.05; p < 0.001) and mean arterial pressure (MAP) (F = 19.2; p < 0.001) also increased significantly during the laparoscopy. No significant correlation was identified between fluid input and urine output during the laparoscopy (r = 0.012; p = 0.953). CONCLUSIONS: Renal hypoxia does not occur during laparoscopic surgery in children if the minimum age-appropriate intra-abdominal pressures are used. Alternative causes must account for the oliguria and anuria demonstrated in children undergoing laparoscopy.

Update in the management of aortic dissection.

OPINION STATEMENT: Recent improvements in diagnosis, peri-operative management, surgical techniques and postoperative care have resulted in decreased mortality and morbidity in acute aortic dissections (AAD). The classic treatment algorithm indicates that type A patients require direct surgical intervention and type B patients should be treated medically, in absence of complications. Initial medical treatment is adopted in all AAD patients, as it reduces propagation of the dissection and aortic rupture. In type A aortic dissection (TAAD) several techniques have contributed to major changes in the surgical approach, such as cerebral protection using moderate circulatory arrest, selective cerebral perfusion, and aortic valve sparing with root replacement. In TAAD with involvement of the descending aorta, thoracic endovascular aortic repair (TEVAR) can be performed as a part of a complex hybrid procedure, in which surgical ascending/arch repair is combined with the placement of a stent graft in the descending aorta. Future developments in stent graft technologies might broaden the usefulness of TEVAR for the total endovascular repair of TAAD. In complicated type B aortic dissection (TBAD), the use of TEVAR has become the therapy of first choice. By covering the proximal entry tear, the stent graft reduces the pressurization of the false lumen, treating malperfusion and inducing favorable aortic remodeling. In uncomplicated TBAD, TEVAR has been used to prevent long term complications, such as aortic aneurysm, but this concept is not yet routinely recommended. Regardless of their initial treatment, all AAD patients should be administered with strict antihypertensive management combined with imaging surveillance and careful periodic clinical follow-up.

Contemporary Role of Computational Analysis in Endovascular Treatment for Thoracic Aortic Disease.

In the past decade, thoracic endovascular aortic repair (TEVAR) has become the primary treatment option in descending aneurysm and dissection. The clinical outcome of this minimally invasive technique is strictly related to an appropriate patient/stent graft selection, hemodynamic interactions, and operator skills. In this context, a quantitative assessment of the biomechanical stress induced in the aortic wall due to the stent graft may support the planning of the procedure. Different techniques of medical imaging, like computed tomography or magnetic resonance imaging, can be used to evaluate dynamics in the thoracic aorta. Such information can also be combined with dedicated patient-specific computer-based simulations, to provide a further insight into the biomechanical aspects. In clinical practice, computational analysis might show the development of aortic disease, such as the aortic wall segments which experience higher stress in places where rupture and dissection may occur. In aortic dissections, the intimal tear is usually located at the level of the sino-tubular junction and/or at the origin of the left subclavian artery. Besides, computational models may potentially be used preoperatively to predict stent graft behavior, virtually testing the optimal stent graft sizing, deployment, and conformability, in order to provide the best endovascular treatment. The present study reviews the current literature regarding the use of computational tools for TEVAR biomechanics, highlighting their potential clinical applications.

Comparison of in-hospital morbidity and mortality in HIV-infected and uninfected children after surgery.

PURPOSE: Increasingly HIV-infected children can be expected to require surgery. The aim of this study was to compare the outcome of HIV-infected and HIV-unexposed children undergoing surgery. PATIENTS AND METHODS: A prospective study of children less than or equal to 60 months admitted to a tertiary pediatric surgical service from July 2004 to July 2008. Children underwent age-definitive HIV testing and were followed up postoperatively for complications, length of stay and mortality. RESULTS: Three hundred and twenty-seven children were enrolled: 82 (23 %) HIV-infected and 245 (67 %) were HIV-unexposed. Eighty-four (26 %) children were malnourished, which was higher in the HIV-infected group [41 (50.0 %) vs. 43 (17.5 %), relative risk (RR) 2.9; 95 % confidence interval (CI) 2.0-4.1; p < 0.0001]. Three hundred and twenty-eight surgical procedures were performed. A similar number of major [28 (34.2 %) vs. 64 (26.1 %); p = 0.2] and emergency procedures [37 (45.1 %) vs. 95 (38.8 %); p = 0.34] were performed in each group. HIV-infected children had a higher rate of contamination at surgery [40 (48.7 %) vs. 49 (20 %); RR 2.43 (CI 1.7-3.4); p < 0.0001]. There were more complications in the HIV-infected group [34 (41.5 %) vs. 14 (5.7 %); RR 7.3 (CI 4.1-12.8); p < 0.0001]. The most common complications were surgical site complications 30 (55 %), followed by postoperative infections, 19 (34 %). Infections with drug-resistant organisms occurred more commonly in HIV-infected children [11/19 (58 %) vs. 2/13 (15 %); RR 3.8 (CI 1.3-14.2); p = 0.02]. The median length of hospital stay was longer in the HIV-infected group [4 (IQR 2-14) vs. 2 (IQR 1-4) days; p = 0.0001]. There was a higher mortality amongst the HIV-infected group [6 (7.3 %) vs. 0 (0 %); p < 0.0001]. CONCLUSION: HIV-infected children have a higher rate of postoperative complications and mortality compared with HIV-unexposed children.

Outcome of HIV-exposed uninfected children undergoing surgery.

BACKGROUND: HIV-exposed uninfected (HIVe) children are a rapidly growing population that may be at an increased risk of illness compared to HIV-unexposed children (HIVn). The aim of this study was to investigate the morbidity and mortality of HIVe compared to both HIVn and HIV-infected (HIVi) children after a general surgical procedure. METHODS: A prospective study of children less than 60 months of age undergoing general surgery at a paediatric referral hospital from July 2004 to July 2008 inclusive. Children underwent age-definitive HIV testing and were followed up post operatively for the development of complications, length of stay and mortality. RESULTS: Three hundred and eighty children were enrolled; 4 died and 11 were lost to follow up prior to HIV testing, thus 365 children were included. Of these, 38(10.4%) were HIVe, 245(67.1%) were HIVn and 82(22.5%) were HIVi children.The overall mortality was low, with 2(5.2%) deaths in the HIVe group, 0 in the HIVn group and 6(7.3%) in the HIVi group (p = 0.0003). HIVe had a longer stay than HIVn children (3 (2-7) vs. 2 (1-4) days p = 0.02). There was no significant difference in length of stay between the HIVe and HIVi groups. HIVe children had a higher rate of complications compared to HIVn children, (9 (23.7%) vs. 14(5.7%) (RR 3.8(2.1-7) p < 0.0001) but a similar rate of complications compared to HIVi children 34 (41.5%) (RR = 0.6 (0.3-1.1) p = 0.06). CONCLUSION: HIVe children have a higher risk of developing complications and mortality after surgery compared to HIVn children. However, the risk of complications is lower than that of HIVi children.

Predictors of postoperative complications in HIV-infected children undergoing surgery.

BACKGROUND: An increasing number of HIV-infected children require a surgical procedure. The aim of this study was to investigate factors associated with the development of complications in HIV-infected children undergoing surgery. METHODS: A prospective study of HIV-infected children younger than 60 months undergoing surgery at a tertiary referral pediatric hospital from July 2004 to July 2008 was performed. Children were followed postoperatively for the development of complications, length of stay, and mortality. RESULTS: Eighty-two HIV-infected children, with a median age of 11.5 months (interquartile range, 6-24 months), were enrolled. Most (68; 82.9%) had World Health Organization stage 3 or 4 HIV disease, 72 (88%) had Centers for Disease Control and Prevention stage 2 or 3 disease, and 60 (73%) were taking highly active antiretroviral therapy. Half (41; 50%) were underweight, 37 (45.1%) underwent emergency surgery, 28 (34.2%) required major surgery, and 40 (48.7%) had surgical site contamination at the time of surgery. The median length of hospital stay was 4 days (interquartile range, 2-14 days), and in-hospital mortality was 6 (7%). Thirty-four (42%) children developed 37 complications. On univariate analysis, malnutrition, HIV stage, or type of surgery was not associated with development of complications. In contrast, young age (6 vs 13.5 months; P = .0004), low hemoglobin (9.6 vs 10.5 g/dL; P = .04), or having a major procedure (14 [42%] vs 9 [18%]; P = .03; relative risk, 2.2 [1.2-4.8]) was associated with complications. On logistic regression, younger age (odds ratio = 4.3; P = .004; 95% confidence interval, 1.6-11.9) and major surgery (odds ratio = 6.8; P = .001; 95% confidence interval, 1.5-31.4) were associated with development of a complication. CONCLUSION: Young age and major surgery were the main predicators of complications in HIV-infected children undergoing surgery.