Improving the efficiency of abdominal aortic aneurysm wall stress computations.

An abdominal aortic aneurysm is a pathological dilation of the abdominal aorta, which carries a high mortality rate if ruptured. The most commonly used surrogate marker of rupture risk is the maximal transverse diameter of the aneurysm. More recent studies suggest that wall stress from models of patient-specific aneurysm geometries extracted, for instance, from computed tomography images may be a more accurate predictor of rupture risk and an important factor in AAA size progression. However, quantification of wall stress is typically computationally intensive and time-consuming, mainly due to the nonlinear mechanical behavior of the abdominal aortic aneurysm walls. These difficulties have limited the potential of computational models in clinical practice. To facilitate computation of wall stresses, we propose to use a linear approach that ensures equilibrium of wall stresses in the aneurysms. This proposed linear model approach is easy to implement and eliminates the burden of nonlinear computations. To assess the accuracy of our proposed approach to compute wall stresses, results from idealized and patient-specific model simulations were compared to those obtained using conventional approaches and to those of a hypothetical, reference abdominal aortic aneurysm model. For the reference model, wall mechanical properties and the initial unloaded and unstressed configuration were assumed to be known, and the resulting wall stresses were used as reference for comparison. Our proposed linear approach accurately approximates wall stresses for varying model geometries and wall material properties. Our findings suggest that the proposed linear approach could be used as an effective, efficient, easy-to-use clinical tool to estimate patient-specific wall stresses.

A systematic review of assessment of skill acquisition and operative competency in vascular surgical training.

OBJECTIVE: The aim of this systematic review is to describe the literature and assessment tools evaluating vascular surgical operative performance that could potentially be used for the assessment of educational outcomes applicable to the Milestone Project and the Next Accreditation System. METHODS: A systematic review of PubMed/MEDLINE, EMBASE, PsycINFO, and key journals from 1985 to 2013 was performed to identify English-language articles describing assessment of vascular surgical skills and competence. Qualifying studies were abstracted for data concerning study aims, study and assessment setting, skills measured, and metrics used to determine competency. Strengths, weaknesses, and psychometric robustness of the assessment tools were determined. RESULTS: The literature search identified 617 citations. After title and abstract review, 65 articles were retrieved for full-text assessment and 48 articles were included in the final review. Twenty-nine articles assessed open vascular skills; 19, endovascular skills; six, nontechnical skills; and one, teamwork skills. The majority (84%) of studies were performed in a simulated environment, four (8%) were performed in the operating room, and the remaining three were performed in both a simulated environment and an operating room. Strengths and weaknesses of assessment tools were study and assessor dependent, with none applicable to all study scenarios or procedures. CONCLUSIONS: The literature describing assessment tools pertinent to vascular surgery is diverse. Existing assessment tools may be relevant to individual technical skill acquisition assessment; however, an operative assessment tool relevant to vascular/endovascular surgery and generalizable to the wide spectrum of technical and nontechnical skills pertinent to vascular surgery needs to be developed, validated, and implemented to allow the practical assessment of resident readiness to operate in an unsupervised setting.

Lower extremity autologous vein bypass for critical limb ischemia is not adversely affected by prior endovascular procedure.

OBJECTIVE: It has been reported that a failed endovascular intervention adversely affects results of lower extremity bypass (LEB). We reviewed rates of prior endovascular intervention (PEI) in patients undergoing LEB with autologous vein for critical limb ischemia (CLI) to determine effects on graft patency, limb salvage, and amputation-free survival. METHODS: Retrospective review was conducted of consecutive autologous vein LEBs performed for CLI between 2005 and 2012 at a tertiary care academic medical center. RESULTS: Overall, 314 autologous vein LEBs were performed for CLI, 71% for tissue loss. TransAtlantic Inter-Society Consensus II type D or type C lesions were present in 62% and 25%, respectively. The great saphenous vein was used as a conduit in 83%, and the distal target was infrapopliteal in 60%. The 30-day mortality rate was 3.5%. Primary patency rates at 1 year and 5 years were 61% and 45%. Secondary patency rates at 1 year and 5 years were 88% and 64%, with 23% requiring an intervention to maintain patency. The 5-year limb salvage rate was 89%, and the 5-year amputation-free survival was 49%. There were 61 patients (19%) who had undergone a PEI and 253 (81%) who underwent bypass with no prior endovascular intervention (NPEI). There were 19 iliac stents, 29 femoral interventions, 13 popliteal interventions, 9 crural interventions, 9 infrainguinal thrombectomies, and 13 infrainguinal thrombolyses. PEI and NPEI patients had similar demographics and prevalence of atherosclerotic risk factors. The 1-year primary patency rate was 62% for NPEI patients vs 59% for PEI patients (P = .759). The 1-year and 2-year secondary patency rates were 87% and 79% for NPEI patients vs 89% and 78% for PEI patients (P = .947). The 3-year limb salvage rate was 89% for NPEI patients vs 92% for PEI patients (P = .445). The 3-year amputation-free survival was 59% for NPEI patients vs 52% for PEI patients (P = .399). Median follow-up time was 323 days for NPEI patients (interquartile range, 83-918) vs 463 days for PEI patients (interquartile range, 145-946; P = .275). CONCLUSIONS: Overall operative mortality, patency rates, and limb salvage for autologous vein LEB in CLI patients continue to be excellent in the endovascular era and are not necessarily affected by a prior ipsilateral endovascular procedure. Long-term survival remains poor in CLI patients requiring LEB.

Open versus endoscopic great saphenous vein harvest for lower extremity revascularization of critical limb ischemia.

OBJECTIVE: This study determined wound complication rates, intervention rates, failure mechanisms, patency, limb salvage, and overall survival after lower extremity revascularization using open vein harvest (OVH) vs endoscopic vein harvest (EVH) for critical limb ischemia. METHODS: A single-institution review was conducted of consecutive patients who underwent infrainguinal bypass with a single-segment reversed great saphenous vein between 2005 and 2012. RESULTS: A total of 251 patients with critical limb ischemia underwent revascularization, comprising 153 with OVH and 98 with EVH. The OVH group had a lower mean body mass index (26.7 vs 29.9 kg/m(2); P = .001). There were no other differences in demographics, comorbidities, medications, smoking, or in the proximal or distal anastomotic site. Median operative times were 249 minutes (OVH) vs 316 minutes (EVH; P < .001). Median postoperative hospital length of stay was 7 days (OVH) vs 5 days (EVH; P < .001). Median follow-up was 295 days (OVH) vs 313 days (EVH; P = .416). During follow-up, 21 OVH grafts (14%) and 27 EVH grafts (28%) underwent an intervention (P = .048). There were a similar number of surgical interventions: 50% (OVH) vs 61% (EVH; P = .449). Failed grafts had a mean of 1.2 stenoses per graft, regardless of harvest method. Median stenosis length was 2.1 cm (OVH) vs 2.5 cm (EVH; P = .402). At 1 and 3 years, the primary patency was 71% and 52% (OVH) vs 58% and 41% (EVH; P = .010), and secondary patency was 88% and 71% (OVH) vs 88% and 64% (EVH; P = .266). A secondary patency Cox proportional hazard model showed EVH had a hazard ratio of 2.93 (95% confidence interval, 1.03-8.33; P = .044). Overall and harvest-related wound complications were 44% and 29% (OVH) vs 37% and 12% (EVH; P = .226 and P = .002). At 5 years, amputation-free survival was 48% (OVH) vs 54% (EVH; P = .305), and limb salvage was 89% (OVH) and 91% (EVH; P = .615). CONCLUSIONS: OVH and EVH have similar failure mechanisms, limb salvage, amputation-free survival, and overall survival. EVH is associated with impaired patency, increased need for intervention, longer operative times, shorter hospital stays, and decreased vein harvest site wound complications. OVH of the great saphenous vein may provide optimal patency but was not necessarily associated with better patient-centered outcomes. Similar limb salvage rates and amputation-free survival may justify the use of EVH, despite inferior patency, to capture shorter hospital stays and decreased wound complications.

Bilateral mechanical rotational vertebral artery occlusion.

Rotational vertebral artery occlusion, or bow hunter's stroke, is reversible, positional symptomatic vertebrobasilar ischemia. The typical mechanism of action is obstruction of a dominant vertebral artery with contralateral head rotation in the setting of baseline ipsilateral vertebral artery stenosis or occlusion. Here we present a rare case of mechanical occlusion of bilateral patent vertebral arteries manifesting as near syncope with rightward head rotation. Diagnostic cerebral angiography showed dynamic right C5 vertebral occlusion and left C2 vertebral occlusion. The patient underwent right C4/5 transverse process decompression. Postoperative angiogram showed patent flow through the right vertebral artery in neutral position and with head turn with resultant resolution of symptoms.

Buerger's disease.

Buerger's disease (thromboangiitis obliterans) is a nonatherosclerotic segmental inflammatory disease of small- and medium-sized arteries of the distal extremities of predominantly young male tobacco users. Early symptoms may include episodic pain and coldness in fingers, and late findings may present as intermittent claudication, skin ulcers, or gangrene requiring eventual amputation. Tobacco cessation is the cornerstone of treatment. Other modalities of reducing pain or avoiding amputation have not been as successful. This review summarizes in tabular form the types of treatment that have been used, including therapeutic angiogenesis.

Obesity is not an independent risk factor for adverse perioperative and long-term clinical outcomes following open AAA repair or EVAR.

OBJECTIVES: Moderate (body mass index [BMI] ≥30) and morbid obesity (BMI ≥35) is increasing at an alarming rate in vascular surgery patients. The objective of this study was to determine the impact of obesity on perioperative and long-term clinical outcomes following open abdominal aortic aneurysm (AAA) repair or endovascular aneurysm repair (EVAR). METHODS: This review includes patients that underwent open AAA repair (n = 403) or EVAR (n = 223) from 1999 to 2009. Specific patient characteristics such as comorbid diseases, medications, and body mass index (BMI) were assessed. Specific perioperative outcomes such as length of stay, myocardial infarctions, and mortality were reviewed. In addition, long-term outcomes such as rates of reintervention, permanent renal dysfunction, and mortality beyond 30 days were also assessed. RESULTS: The incidence of obesity in open AAA patients was 25.3% (documented incidence 1.5%) and for EVAR was 24.6% (documented incidence 4%). Moderate and morbid obesity was associated with longer intensive care unit (ICU) admissions for both open AAA or EVAR patients (P < .05). However, no significant differences in perioperative outcomes in terms of overall length of stay, myocardial infarction, acute renal failure, wound infections, or mortality were noted between obese and nonobese patients underoing open AAA repair or EVAR (P > .05). Similarly, moderate and morbid obesity was not associated with significant differences in rates of reintervention, permanent renal dysfunction, and mortality beyond 30 days for patients undergoing open AAA repair or EVAR (P > .05). CONCLUSIONS: The results of this study indicate that moderate and morbid obesity are not independently associated with adverse perioperative and long-term clinical outcomes for patients undergoing open AAA repair or EVAR. Therefore, either open AAA repair or EVAR can be accomplished safely in moderately obese and morbidly obese patients.

Recent trends in clinical outcomes and resource utilization for pulmonary embolism in the United States: findings from the nationwide inpatient sample.

BACKGROUND: Pulmonary embolism (PE) has been cited as the most common preventable cause of death in hospitalized patients. The objectives of this study were to determine recent trends in clinical outcomes and resource utilization for hospitalized patients with a clinically recognized episode of acute PE. METHODS: Patients with primary or secondary PE who had been discharged from US acute care hospitals were identified from the Nationwide Inpatient Sample during the 8-year period between 1998 and 2005. The major clinical outcomes assessed included hospital mortality and length of hospitalization. To assess resource utilization for the treatment of PE, average hospital charges for these admissions were assessed, normalized to 2005 US dollars, and adjusted to reflect the US consumer price index. RESULTS: Between 1998 and 2005, the number of patients with primary or secondary PE on discharge from the hospital increased from 126,546 to 229,637; hospital case fatality rates for these patients decreased from 12.3 to 8.2% (p < 0.001); length of hospital stay decreased from 9.4 days to 8.6 days (p < 0.001); and total hospital charges increased from $25,293 to $43,740 (p < 0.001). CONCLUSIONS: Between 1998 and 2005, significant improvements were observed in outcomes for patients hospitalized for clinically recognized PE, including decreases in mortality and length of hospital stay. Charges for this hospital care increased during this time period.

Interleukin 18 binding protein (IL18-BP) inhibits neointimal hyperplasia after balloon injury in an atherosclerotic rabbit model.

OBJECTIVES: Interleukin 18 (IL18) is an interferon (IFN)-gamma-inducing factor and a proinflammatory and proatherogenic cytokine. IL18 binding protein (IL18-BP) functions as an IL18 inhibitor. This study was designed to investigate whether systemic administration of IL18-BP could inhibit neointimal hyperplasia and arterial lipid deposition. METHODS: New Zealand white, male rabbits were fed with a 21% fat, 0.15% cholesterol diet. The left superficial femoral artery (SFA) was de-endotheliazed with a 2F arterial embolectomy catheter. IL18-BP (5 microg, 10 microg, or 25 microg), or 0.9% saline (control) was administered by i.v. bolus during surgery. Rabbits were followed-up at 2 and 4 weeks. Intima-media (I/M) and lumen-whole artery (L/A) area ratios, and luminal areas were measured. Serum lipid levels, liver enzymes, and kidney function were evaluated. Inflammatory cells were quantified and further verified with immunohistofluorescence staining. The extent of lipid deposition in the artery wall was quantified with Oil Red O (ORO) staining employing Zeiss AxioVision 4.6.3. Image analysis software. Lipid laden cells including macrophages were evaluated by transmission electron microscopy (TEM). RESULTS: Intravenous IL18-BP 5 microg, 10 microg, and 25 microg significantly reduced I/M ratios compared with the control group at both 2 and 4 weeks. There was no significant difference between the 5 microg and 10 microg dose groups. However, at 10 microg, IL18-BP significantly increased L/A ratio more than either the 5 microg IL18-BP or control groups. The high fat diet caused significant elevation of serum lipids at 4 and 6 weeks. IL18-BP had no effect on blood lipid levels. Lipid deposit in the thoracic aorta of the control group at 6 weeks was more than at 4 weeks (P = .025). Administration of IL18-BP inhibited the lipid deposition at 4 weeks (not significant) and 6 weeks (P = .012 to .008) compared with its control group. Lipid laden macrophages (foam cells), as well as endothelial cells and smooth muscle cells were seen in the descending thoracic aorta after 6 weeks of a high fat diet by ORO, immunohistofluorescence staining, and TEM. The lipid laden cells were not seen in either of IL18-BP groups. IL18-BP 10 microg significantly inhibited mono/macro adherence and infiltration in the SFA after balloon-injury at 2 weeks after surgery. CONCLUSION: A single intravenous dose of IL18-BP significantly decreased arterial neointimal hyperplasia, improved lumen to artery ratio after balloon-injury and also prevented arteriosclerosis progression. CLINICAL RELEVANCE: A single intravenous dose of IL18BP decreased neointimal hyperplasia and improved arterial L/A ratios in an atherosclerotic balloon-injury animal model. These preliminary results suggest that IL18BP may be a promising molecular approach to inhibit neointimal hyperplasia and arteriosclerosis progression following coronary and peripheral angioplasty.

Tissue-engineered lung: an in vivo and in vitro comparison of polyglycolic acid and pluronic F-127 hydrogel/somatic lung progenitor cell constructs to support tissue growth.

In this study, we describe the isolation and characterization of a population of adult-derived or somatic lung progenitor cells (SLPC) from adult mammalian lung tissue and the promotion of alveolar tissue growth by these cells (both in vitro and in vivo) after seeding onto synthetic polymer scaffolds. After extended in vitro culture, differentiating cells expressed Clara cell 10kDa protein, surfactant protein-C, and cytokeratin but did not form organized structures. When cells were combined with synthetic scaffolds, polyglycolic acid (PGA) or Pluronic F-127 (PF-127), and maintained in vitro or implanted in vivo, they expressed lung-specific markers for Clara cells, pneumocytes, and respiratory epithelium and organized into identifiable pulmonary structures (including those similar to alveoli and terminal bronchi), with evidence of smooth muscle development. Although PGA has been shown to be an excellent polymer for culture of specific cell types in vitro, in vivo culture in an immunocompetent host induced a foreign body response that altered the integrity of the developing lung tissue. Use of PF-127/cell constructs resulted in the development of tissue with less inflammatory reaction. These data suggest that the therapeutic use of engineered tissues requires both the use of specific cell phenotypes, as well as the careful selection of synthetic polymers, to facilitate the assembly of functional tissue.