The Impact of Just-in-Time Simulation Training for Healthcare Professionals on Learning and Performance Outcomes: A Systematic Review.

ABSTRACT: Although just-in-time training (JIT) is increasingly used in simulation-based health professions education, its impact on learning, performance, and patient outcomes remains uncertain. The aim of this study was to determine whether JIT simulation training leads to improved learning and performance outcomes. We included randomized or nonrandomized interventional studies assessing the impact of JIT simulation training (training conducted in temporal or spatial proximity to performance) on learning outcomes among health professionals (trainees or practitioners). Of 4077 citations screened, 28 studies were eligible for inclusion. Just-in-time training simulation training has been evaluated for a variety of medical, resuscitation, and surgical procedures. Most JIT simulation training occurred immediately before procedures and lasted between 5 and 30 minutes. Despite the very low certainty of evidence, this systematic review suggests JIT simulation training can improve learning and performance outcomes, in particular time to complete skills. There remains limited data on better patient outcomes and collateral educational effects.

Factors Associated With Improved Pediatric Resuscitative Care in General Emergency Departments.

OBJECTIVES: To describe the quality of pediatric resuscitative care in general emergency departments (GEDs) and to determine hospital-level factors associated with higher quality. METHODS: Prospective observational study of resuscitative care provided to 3 in situ simulated patients (infant seizure, infant sepsis, and child cardiac arrest) by interprofessional GED teams. A composite quality score (CQS) was measured and the association of this score with modifiable and nonmodifiable hospital-level factors was explored. RESULTS: A median CQS of 62.8 of 100 (interquartile range 50.5-71.1) was noted for 287 resuscitation teams from 175 emergency departments. In the unadjusted analyses, a higher score was associated with the modifiable factor of an affiliation with a pediatric academic medical center (PAMC) and the nonmodifiable factors of higher pediatric volume and location in the Northeast and Midwest. In the adjusted analyses, a higher CQS was associated with modifiable factors of an affiliation with a PAMC and the designation of both a nurse and physician pediatric emergency care coordinator, and nonmodifiable factors of higher pediatric volume and location in the Northeast and Midwest. A weak correlation was noted between quality and pediatric readiness scores. CONCLUSIONS: A low quality of pediatric resuscitative care, measured using simulation, was noted across a cohort of GEDs. Hospital factors associated with higher quality included: an affiliation with a PAMC, designation of a pediatric emergency care coordinator, higher pediatric volume, and geographic location. A weak correlation was noted between quality and pediatric readiness scores.

PI3K Inhibition Restores and Amplifies Response to Ruxolitinib in Patients with Myelofibrosis.

PURPOSE: Treatment options are limited beyond JAK inhibitors for patients with primary myelofibrosis (MF) or secondary MF. Preclinical studies have revealed that PI3Kδ inhibition cooperates with ruxolitinib, a JAK1/2 inhibitor, to reduce proliferation and induce apoptosis of JAK2V617F-mutant cell lines. PATIENTS AND METHODS: In a phase I dose-escalation and -expansion study, we evaluated the safety and efficacy of a selective PI3Kδ inhibitor, umbralisib, in combination with ruxolitinib in patients with MF who had a suboptimal response or lost response to ruxolitinib. Enrolled subjects were required to be on a stable dose of ruxolitinib for ≥8 weeks and continue that MTD at study enrollment. The recommended dose of umbralisib in combination with ruxolitinib was determined using a modified 3+3 dose-escalation design. Safety, pharmacokinetics, and efficacy outcomes were evaluated, and spleen size was measured with a novel automated digital atlas. RESULTS: Thirty-seven patients with MF (median age, 67 years) with prior exposure to ruxolitinib were enrolled. A total of 2 patients treated with 800 mg umbralisib experienced reversible grade 3 asymptomatic pancreatic enzyme elevation, but no dose-limiting toxicities were seen at lower umbralisib doses. Two patients (5%) achieved a durable complete response, and 12 patients (32%) met the International Working Group-Myeloproliferative Neoplasms Research and Treatment response criteria of clinical improvement. With a median follow-up of 50.3 months for censored patients, overall survival was greater than 70% after 3 years of follow-up. CONCLUSIONS: Adding umbralisib to ruxolitinib in patients was well tolerated and may resensitize patients with MF to ruxolitinib without unacceptable rates of adverse events seen with earlier generation PI3Kδ inhibitors. Randomized trials testing umbralisib in the treatment of MF should be pursued.

My Cancer Genome: Coevolution of Precision Oncology and a Molecular Oncology Knowledgebase.

PURPOSE: The My Cancer Genome (MCG) knowledgebase and resulting website were launched in 2011 with the purpose of guiding clinicians in the application of genomic testing results for treatment of patients with cancer. Both knowledgebase and website were originally developed using a wiki-style approach that relied on manual evidence curation and synthesis of that evidence into cancer-related biomarker, disease, and pathway pages on the website that summarized the literature for a clinical audience. This approach required significant time investment for each page, which limited website scalability as the field advanced. To address this challenge, we designed and used an assertion-based data model that allows the knowledgebase and website to expand with the field of precision oncology. METHODS: Assertions, or computationally accessible cause and effect statements, are both manually curated from primary sources and imported from external databases and stored in a knowledge management system. To generate pages for the MCG website, reusable templates transform assertions into reconfigurable text and visualizations that form the building blocks for automatically updating disease, biomarker, drug, and clinical trial pages. RESULTS: Combining text and graph templates with assertions in our knowledgebase allows generation of web pages that automatically update with our knowledgebase. Automated page generation empowers rapid scaling of the website as assertions with new biomarkers and drugs are added to the knowledgebase. This process has generated more than 9,100 clinical trial pages, 18,100 gene and alteration pages, 900 disease pages, and 2,700 drug pages to date. CONCLUSION: Leveraging both computational and manual curation processes in combination with reusable templates empowers automation and scalability for both the MCG knowledgebase and MCG website.

Rapid reversal of a potentially constraining genetic covariance between leaf and flower traits in Silene latifolia.

Genetic covariance between two traits generates correlated responses to selection, and may either enhance or constrain adaptation. Silene latifolia exhibits potentially constraining genetic covariance between specific leaf area (SLA) and flower number in males. Flower number is likely to increase via fecundity selection but the correlated increase in SLA increases mortality, and SLA is under selection to decrease in dry habitats. We selected on trait combinations in two selection lines for four generations to test whether genetic covariance could be reduced without significantly altering trait means. In one selection line, the genetic covariance changed sign and eigenstructure changed significantly, while in the other selection line eigenstructure remained similar to the control line. Changes in genetic variance-covariance structure are therefore possible without the introduction of new alleles, and the responses we observed suggest that founder effects and changes in frequency of alleles of major effect may be acting to produce the changes.

Internet-Based Assessment of Oncology Health Care Professional Learning Style and Optimization of Materials for Web-Based Learning: Controlled Trial With Concealed Allocation.

BACKGROUND: Precision medicine has resulted in increasing complexity in the treatment of cancer. Web-based educational materials can help address the needs of oncology health care professionals seeking to understand up-to-date treatment strategies. OBJECTIVE: This study aimed to assess learning styles of oncology health care professionals and to determine whether learning style-tailored educational materials lead to enhanced learning. METHODS: In all, 21,465 oncology health care professionals were invited by email to participate in the fully automated, parallel group study. Enrollment and follow-up occurred between July 13 and September 7, 2015. Self-enrolled participants took a learning style survey and were assigned to the intervention or control arm using concealed alternating allocation. Participants in the intervention group viewed educational materials consistent with their preferences for learning (reading, listening, and/or watching); participants in the control group viewed educational materials typical of the My Cancer Genome website. Educational materials covered the topic of treatment of metastatic estrogen receptor-positive (ER+) breast cancer using cyclin-dependent kinases 4/6 (CDK4/6) inhibitors. Participant knowledge was assessed immediately before (pretest), immediately after (posttest), and 2 weeks after (follow-up test) review of the educational materials. Study statisticians were blinded to group assignment. RESULTS: A total of 751 participants enrolled in the study. Of these, 367 (48.9%) were allocated to the intervention arm and 384 (51.1%) were allocated to the control arm. Of those allocated to the intervention arm, 256 (69.8%) completed all assessments. Of those allocated to the control arm, 296 (77.1%) completed all assessments. An additional 12 participants were deemed ineligible and one withdrew. Of the 552 participants, 438 (79.3%) self-identified as multimodal learners. The intervention arm showed greater improvement in posttest score compared to the control group (0.4 points or 4.0% more improvement on average; P=.004) and a higher follow-up test score than the control group (0.3 points or 3.3% more improvement on average; P=.02). CONCLUSIONS: Although the study demonstrated more learning with learning style-tailored educational materials, the magnitude of increased learning and the largely multimodal learning styles preferred by the study participants lead us to conclude that future content-creation efforts should focus on multimodal educational materials rather than learning style-tailored content.

My Cancer Genome: Evaluating an Educational Model to Introduce Patients and Caregivers to Precision Medicine Information.

This study tested an innovative model for creating consumer-level content about precision medicine based on health literacy and learning style principles. "Knowledge pearl" videos, incorporating multiple learning modalities, were created to explain genetic and cancer medicine concepts. Cancer patients and caregivers (n=117) were randomized to view professional-level content directly from the My Cancer Genome (MCG) website (Group A; control), content from MCG with knowledge pearls embedded (Group B), or a consumer translation, targeted at the sixth grade level, with knowledge pearls embedded (Group C). A multivariate analysis showed that Group C, but not Group B, showed greater knowledge gains immediately after viewing the educational material than Group A. Statistically significant group differences in test performance were no longer observed three weeks later. These findings suggest that adherence to health literacy and learning style principles facilitates comprehension of precision medicine concepts and that ongoing review of the educational information is necessary.

Guiding Oncology Patients Through the Maze of Precision Medicine.

As the role of genomics in health care grows, patients increasingly require adequate genetic literacy to fully engage in their care. This study investigated a model for delivering consumer-friendly genetic information to improve understanding of precision medicine using health literacy and learning style principles. My Cancer Genome (MCG), a freely available cancer decision support tool, was used as a testbed. MCG content on a melanoma tumor mutation, BRAF V600E, was translated to a 6th-grade reading level, incorporating multiple learning modalities. A total of 90 patients and caregivers were recruited from a melanoma clinic at an academic medical center and randomized to 3 groups. Group A (control) received an exact copy of text from MCG. Group B was given the same content with hyperlinks to videos explaining key genetic concepts, identified and labeled by the team as knowledge pearls. Group C received the translated content with the knowledge pearls embedded. Changes in knowledge were measured through pre and post questionnaires. Group C showed the greatest improvement in knowledge. The study results demonstrate that providing information based on health literacy and learning style principles can improve patients' understanding of genetic concepts, thus increasing their likelihood of taking an active role in any decision making concerning their health.

The Path(way) Less Traveled: A Pathway-Oriented Approach to Providing Information about Precision Cancer Medicine on My Cancer Genome.

This perspective describes the motivation, development, and implementation of pathway-based content for My Cancer Genome, an online precision medicine knowledge resource describing clinical implications of genetic alterations in cancer. As researchers uncover more about cancer pathogenesis, we are learning more not only about the specific genes and proteins involved but also about how those genes and proteins interact with others along cell signaling pathways. This knowledge has led researchers and clinicians to begin to think about cancer therapy using a pathway-based approach. To facilitate this approach, My Cancer Genome used a list of more than 800 cancer-related genes to identify 20 cancer-relevant pathways and then created content focused on demonstrating the therapeutic relevance of these pathways.

Validation of a pediatric bedside tool to predict time to death after withdrawal of life support.

AIM: To evaluate the accuracy of a tool developed to predict timing of death following withdrawal of life support in children. METHODS: Pertinent variables for all pediatric deaths (age ≤ 21 years) from 1/2009 to 6/2014 in our pediatric intensive care unit (PICU) were extracted through a detailed review of the medical records. As originally described, a recently developed tool that predicts timing of death in children following withdrawal of life support (dallas predictor tool [DPT]) was used to calculate individual scores for each patient. Individual scores were calculated for prediction of death within 30 min (DPT30) and within 60 min (DPT60). For various resulting DPT30 and DPT60 scores, sensitivity, specificity and area under the receiver operating characteristic curve were calculated. RESULTS: There were 8829 PICU admissions resulting in 132 (1.5%) deaths. Death followed withdrawal of life support in 70 patients (53%). After excluding subjects with insufficient data to calculate DPT scores, 62 subjects were analyzed. Average age of patients was 5.3 years (SD: 6.9), median time to death after withdrawal of life support was 25 min (range; 7 min to 16 h 54 min). Respiratory failure, shock and sepsis were the most common diagnoses. Thirty-seven patients (59.6%) died within 30 min of withdrawal of life support and 52 (83.8%) died within 60 min. DPT30 scores ranged from -17 to 16. A DPT30 score ≥ -3 was most predictive of death within that time period, with sensitivity = 0.76, specificity = 0.52, AUC = 0.69 and an overall classification accuracy = 66.1%. DPT60 scores ranged from -21 to 28. A DPT60 score ≥ -9 was most predictive of death within that time period, with sensitivity = 0.75, specificity = 0.80, AUC = 0.85 and an overall classification accuracy = 75.8%. CONCLUSION: In this external cohort, the DPT is clinically relevant in predicting time from withdrawal of life support to death. In our patients, the DPT is more useful in predicting death within 60 min of withdrawal of life support than within 30 min. Furthermore, our analysis suggests optimal cut-off scores. Additional calibration and modifications of this important tool could help guide the intensive care team and families considering DCD.

Hospital-based emergency department visits in children with motor vehicle traffic accidents: estimates from the nationwide emergency department sample.

BACKGROUND: The purpose of this study is to provide nationally representative estimates of children visiting hospital-based emergency departments (ED) for motor vechicle traffic accidents (MVTA) in the United States during the year of 2008. METHODS: Nationwide Emergency Department Sample for 2008 was used. All pediatric (age ≤18 years) ED visits with external cause for injury ICD-9-diagnostic codes for MVTA were selected. Outcomes examined included discharge status following ED visit and presence of concomitant injuries. Descriptive statistics was used to summarize the estimates. RESULTS: Totally 604 027 hospital-based ED visits occurred in the United States among children (age ≤18 years) due to MVTA. Following an ED visit, 91% were discharged routinely, while 6% were admitted as inpatients into the same hospital. A total of 928 children died in the ED. A total of 34 004 ED visits required inpatient admission into the same hospital and 768 patients died during hospitalization. Mean charge per ED visit was $1887 and total ED charges across the United States were close to $970 million. Among those admitted into the same hospital following ED visit (n=34 004), the mean hospitalization charge was $53 726 and total hospitalization charge across the entire United States were $1.8 billion. CONCLUSIONS: Study findings illustrate the burden associated with pediatric ED visits due to MVTA. Close to $970 million of hospital charges were incurred by children who made an ED visit due to a MVTA during 2008 and about $1.8 billion was incurred among those hospitalized following an ED visit.

Epidemiology of hospital-based emergency department visits due to sports injuries.

BACKGROUND: Sports-related injuries in adolescents incur a significant amount of hospital resources. Sports-related injuries are not an uncommon cause of ED visit; however, national estimates of such injuries in teenagers are unknown. OBJECTIVES: The aim of this study was to identify and characterize emergency department (ED) visits that result from sports-related injuries among teenagers across the United States. This study describes the outcomes associated with sports-related injuries necessitating ED visits among teenagers at a national level. STUDY DESIGN: This is a descriptive epidemiology study. METHODS: The 2008 Nationwide Emergency Department Sample data set, the largest all-payer health care database in the United States, was used to identify ED visits with external cause of injury related to sports occurring in patients aged 13 through 19 years. Outcomes examined included discharge status after the ED visit and presence of concomitant injuries. Descriptive statistics was used to summarize the estimates. Nationwide representative estimates were computed using the discharge weight variable. RESULTS: There were 432,609 ED visits by those between the ages of 13 and 19 years who experienced sports-related injuries, with total charges close to $447.4 million, with a mean total per-visit charge of $1205. The male patients accounted for 76.8% of the total ED visits. The most frequently occurring injuries were superficial injury or contusion (n = 118,250 ED visits); sprains and strains (n = 105,476); fracture of the upper limb (n = 63,151); open wounds of the head, the neck, and the trunk (n = 46,176); as well as intracranial injury (n = 30,726). Close to 29% of all ED visits occurred among those residing in geographical areas with median household income levels of greater than $64,000. After the ED visit, 1.6% were admitted to the same hospital, with a mean length of stay of 2.4 days and a mean hospital charge for ED visit and inpatient services of $22,703. The male patients composed 87.5% of the hospitalizations. The total of hospitalization charges across the entire United States was $154.8 million. CONCLUSIONS: Sports injuries account for a substantial number of 2008 teenage ED visits in the United States. Patient- and hospital-level characteristics were analyzed and highlighted.

Children in the United States make close to 200,000 emergency department visits due to poisoning each year.

OBJECTIVE: The aim of this study was to provide nationally representative hospital-based emergency department (ED) estimate visits in children (aged ≤ 18 y) attributed to poisoning in the United States in 2008. METHODS: Nationwide Emergency Department Sample for the year 2008 was used. All ED visits among children (aged ≤ 18 y) with an external cause of injury for "poisoning" were selected for analysis. Demographic characteristics of the ED visits and outcomes examined included ED charges (EDCs), hospitalization charges (HCs), length of stay in hospital, and disposition after ED visit. RESULTS: During the year 2008, a total of 191,197 ED visits were attributed to poisoning with close to 56% of all ED visits occurring among those aged younger than 4 years. Boys comprised approximately 54% of all ED visits. After an ED visit, 87% were routinely discharged, and 7.3% were admitted into the same hospital. Forty-eight children died in the ED. The frequently reported poisonings included accidental poisoning by other drugs (44,219 ED visits); accidental poisoning by other gases and vapors (27,035 ED visits); and accidental poisoning by analgesics, antipyretics, and antirheumatics (22,334 ED visits). The mean EDC per visit was $1077. The total EDC across the entire United States was $171.8 million. Mean length of stay was 1.9 days. Among those who were hospitalized, the mean HC was $11,792. The total HC across the entire United States was $162.3 million. CONCLUSIONS: The current study provides nationally representative estimates of ED visits attributed to poisoning among children in the United States. High-risk groups and economics associated with treating these injuries are estimated.

Beyond histology: translating tumor genotypes into clinically effective targeted therapies.

Increased understanding of intertumoral heterogeneity at the genomic level has led to significant advancements in the treatment of solid tumors. Functional genomic alterations conferring sensitivity to targeted therapies can take many forms, and appropriate methods and tools are needed to detect these alterations. This review provides an update on genetic variability among solid tumors of similar histologic classification, using non-small cell lung cancer and melanoma as examples. We also discuss relevant technological platforms for discovery and diagnosis of clinically actionable variants and highlight the implications of specific genomic alterations for response to targeted therapy.

The use of extubation readiness parameters: a survey of pediatric critical care physicians.

BACKGROUND: The pediatric literature addressing extubation readiness parameters and strategies to wean from mechanical ventilation is limited. METHODS: We designed a survey to assess the use of extubation readiness parameters among pediatric critical care physicians at academic centers in the United States. RESULTS: The overall response rate was 44.1% (417/945). The majority of respondents check for air leak and the amount of tracheal secretions. Fewer respondents use sedation score, the rapid shallow breathing index, or the airway-occlusion pressure 0.1 s after the start of inspiratory flow prior to extubation. The majority perform a spontaneous breathing trial with pressure support. The majority consider 30 cm H2O as the upper limit of an air leak test, and the need for endotracheal suctioning once every 2-4 hours as acceptable for extubation. In preparation for termination of mechanical ventilation the majority daily wean the ventilator rate and/or the pressure support instead of conducting a spontaneous breathing trial. CONCLUSIONS: Most pediatric critical care physicians reported assessing extubation readiness by checking air leak and suctioning need, and less often consider or perform sedation score or the rapid shallow breathing index.

Elimination of a genetic correlation between the sexes via artificial correlational selection.

Genetic correlations between the sexes can constrain the evolution of sexual dimorphism and be difficult to alter, because traits common to both sexes share the same genetic underpinnings. We tested whether artificial correlational selection favoring specific combinations of male and female traits within families could change the strength of a very high between-sex genetic correlation for flower size in the dioecious plant Silene latifolia. This novel selection dramatically reduced the correlation in two of three selection lines in fewer than five generations. Subsequent selection only on females in a line characterized by a lower between-sex genetic correlation led to a significantly lower correlated response in males, confirming the potential evolutionary impact of the reduced correlation. Although between-sex genetic correlations can potentially constrain the evolution of sexual dimorphism, our findings reveal that these constraints come not from a simple conflict between an inflexible genetic architecture and a pattern of selection working in opposition to it, but rather a complex relationship between a changeable correlation and a form of selection that promotes it. In other words, the form of selection on males and females that leads to sexual dimorphism may also promote the genetic phenomenon that limits sexual dimorphism.

Preoperative cerebral oxygen saturation and clinical outcomes in cardiac surgery.

BACKGROUND: The current study was designed to determine the relation between preoperative cerebral oxygen saturation (Sco2), variables of cardiopulmonary function, mortality, and morbidity in a heterogeneous cohort of cardiac surgery patients. METHODS: In this study, 1,178 consecutive patients scheduled for on-pump surgery were prospectively studied. Preoperative Sco2, demographics, N-terminal pro-B-type natriuretic peptide, high-sensitive troponin T, clinical outcomes, and 30-day and 1-yr mortality were recorded. RESULTS: Median additive EuroSCORE was 5 (range: 0-19). Thirty-day and 1-yr mortality and major morbidity (at least two major complications and/or a high-dependency unit stay of at least 10 days) were 3.5%, 7.7%, and 13.3%, respectively. Median minimal preoperative oxygen supplemented Sco2 (Sco2min-ox) was 64% (range: 15-92%). Sco2min-ox was correlated (all: P value <0.0001) with N-terminal pro-B-type natriuretic peptide (ρ: -0.35), high-sensitive troponin T (ρ: -0.28), hematocrit (ρ: 0.34), glomerular filtration rate (ρ: 0.19), EuroSCORE (τ: 0.20), and left ventricular ejection fraction class (τ: 0.12). Thirty-day nonsurvivors had a lower Sco2min-ox than survivors (median 58% [95% CI, 50.7-62%] vs. 64% [95% CI, 64-65%]; P < 0.0001). Receiver-operating curve analysis of Sco2min-ox and 30-day mortality revealed an area-under-the-curve of 0.71 (95% CI, 0.68-0.73%; P < 0.0001) in the total cohort and an area-under-the-curve of 0.77 (95% CI, 0.69-0.86%; P < 0.0001) in patients with a EuroSCORE more than 10. Logistic regression based on different EuroSCORE categories (0-2; 3-5, 6-10, >10), Sco2min-ox, and duration of cardiopulmonary bypass showed that a Sco2min-ox equal or less than 50% is an independent risk factor for 30-day and 1-yr mortality. CONCLUSIONS: Preoperative Sco2 levels are reflective of the severity of cardiopulmonary dysfunction, associated with short- and long-term mortality and morbidity, and may add to preoperative risk stratification in patients undergoing cardiac surgery.

Relaxed pollinator-mediated selection weakens floral integration in self-compatible taxa of Leavenworthia (Brassicaceae).

Natural selection should favor the integration of floral traits that enhance pollen export and import in plant populations that rely upon pollinators. If this is true, then phenotypic correlations between floral traits should weaken in self-fertilizing groups that do not require pollinator visitation to produce seed. We tested this hypothesis in Leavenworthia, a plant genus in which there have been multiple independent losses of the sporophytic self-incompatibility system found throughout the Brassicaceae. In particular, we conducted phylogenetically independent contrasts of floral trait correlations between two pairs of self-incompatible (SI) and self-compatible (SC) sister taxa. In support of the hypothesis that pollinator-mediated selection integrates floral traits, we found that both SC Leavenworthia taxa have weaker overall floral correlations in comparison to sister taxa that rely upon pollinators. The two independently derived SC Leavenworthia flowers have significantly weaker stamen-petal or pistil-petal correlations, respectively, whereas the stamen-pistil correlation remains constant. These patterns suggest that relaxation of pollinator-mediated selection weakens the integration of traits associated with pollen export and import. The retention of high stamen-pistil correlations in the SC taxa of Leavenworthia further implies that the integration of these traits is either constrained or maintained by selection favoring the successful transfer of pollen within flowers to secure self-pollination.

Development of an artificial vessel lined with human vascular cells.

OBJECTIVES: Thrombogenity of small-diameter vascular prostheses might be reduced by complete coverage of the luminal surface with vascular cells. We investigated cell seeding on polyurethane vascular prostheses. METHODS: Thirty polyurethane vascular prostheses were divided into 3 groups of 10 each: group A, diameter of 20 mm and gamma-sterilized; group B, diameter of 4 mm and gamma-sterilized; and group C, diameter of 4 mm and ethylene oxide sterilized. Human smooth muscle cells, fibroblasts, and endothelial cells were isolated from saphenous vein segments and expanded in culture. Five polyurethane vascular prostheses of each group were seeded with endothelial cells alone (mean, 4.8 +/- 1.2 x 10(6) cells), and the remaining 5 polyurethane vascular prostheses were preseeded with a mixed culture of fibroblasts and smooth muscle cells (mean, 7.7 +/- 2.3 x 10(6) cells), followed by endothelial cell seeding (mean, 4.4 +/- 0.9 x 10(6) cells). Seven days after cell seeding, the polyurethane vascular prostheses were perfused under a pulsatile flow (80 pulses/min, 140/80 mm Hg, and 120 mL/min) for 2 hours. Specimens were taken after each seeding procedure both before and after perfusion and then examined both with a scanning electron microscope and immunohistochemically. RESULTS: Isolated endothelial cell seeding revealed better initial adhesion in groups A and B than in group C (63% vs 33%). After 7 days, the cells had covered approximately 80% of the luminal surface in groups A and B, whereas group C cells rounded up and lost adhesion. After perfusion testing of group A and B prostheses, only 10% of the surface was still covered with endothelial cells. Preseeding with the mixed culture again revealed a better initial adhesion in groups A and B compared with that in group C (76% vs 41%). In groups A and B endothelial cell seeding (adhesion, 72%) resulted in a confluent endothelial cell layer. The results of immunohistochemical staining were positive for collagen IV, laminin, CD31, and Factor VIII. In group C only isolated cells were found after each seeding procedure, which rounded up and vanished during the next days. Perfusion testing of group A and B prostheses revealed that the confluent cell layer remained stable, with only small defects (<10% of the surface). The cells stained positivively for endothelial nitric oxide synthase. CONCLUSION: Seeding of a mixed culture out of fibroblasts and smooth muscle cells resulted in improved endothelial cell adhesion and resistance to shear stress. This outcome was caused by an increased synthesis of extracellular matrix proteins. Cell attachment was better on gamma-sterilized polyurethane vascular prostheses compared with on those undergoing ethylene oxide sterilization.

Preseeding with autologous fibroblasts improves endothelialization of glutaraldehyde-fixed porcine aortic valves.

OBJECTIVE: This study represents the development of a treatment and seeding procedure to improve endothelial cellular adhesion on glutaraldehyde-fixed valves. METHODS: Porcine aortic valves were fixed with 0.2% glutaraldehyde. Wall pieces of these valves had either no additional treatment (n = 4), incubation in M199 Earle (1x), with sodium carbonate at 2.2 g/L without l-glutamine for 24 hours (n = 4), or additional pretreatment with 5%, 10%, or 15% citric acid (three groups, n = 4 each). Thereafter the pieces were washed and buffered to a physiologic pH. This was followed by seeding of human endothelial cells (5 x 10(6) cells). On the basis of the results of these pilot tests, complete glutaraldehyde-fixed aortic roots treated with 10% citric acid were subjected to cell seeding. The valves were seeded with endothelial cells (4.3 x 10(6) cells) either alone (n = 4) or in combination with preseeding of autologous fibroblasts (2.4 x 10(7) cells, n = 4). After each seeding procedure specimens of the free wall of the grafts were taken. In addition, one leaflet was taken for histologic examination after endothelial cell seeding, after 7 days, and after 21 days. Finally, two commercially available stentless aortic valve prostheses (Freestyle; Medtronic, Inc, Minneapolis, Minn) were treated with 10% citric acid and seeded with human fibroblasts and endothelial cells. Specimen were taken according to the glutaraldehyde-fixed aortic roots. Specimen of all experiments were examined with scanning electron microscopy. Frozen sections were stained immunohistochemically for collagen IV, factor VIII, and CD31. RESULTS: On untreated glutaraldehyde-fixed aortic wall pieces, only poor adhesion (24%) was seen. No viable cells were found after 1 week. Cellular adhesion was best on aortic wall pieces pretreated with 10% citric acid. After 7 days, the cells formed a confluent layer. Endothelial cell seeding on citric acid-treated complete aortic valves showed 45% adhesion, but no confluent layer was found after 1 week. Preseeding of these valves with autologous fibroblasts resulted in an endothelial cellular adhesion of 76% and a confluent endothelial cell layer after 7 days. The layer remained stable for at least 21 days. Results of staining for collagen IV, factor VIII, and CD31 were positive on the luminal side of these valves, indicating the synthesis of matrix proteins and viability of the cells. Pretreatment of commercially available porcine valves with 10% citric acid and preseeding with autologous fibroblasts followed by endothelial cell seeding resulted in an adhesion of 78%. The cells formed a confluent cell layer after 7 days. CONCLUSIONS: Pretreatment of glutaraldehyde-fixed porcine aortic valves with citric acid established a surface more suitable for cellular attachment. Preseeding these valves with autologous fibroblasts resulted in a confluent endothelial cell layer on the luminal surface. Flow tests and animal experiments are necessary for further assessment of durability and shear stress resistance.