Degradation of engineered polyurethane heart valves in a mechanically demanding environment with variable mixing of polyester and polycarbonate soft segments

Valvular heart disease (VHD) is a major source of morbidity and mortality leading to approximately 290,000 valve replacement surgeries worldwide each year. Current replacement prosthetics include mechanical and bioprosthetic heart valves, which are burdened by chronic anticoagulation therapy and tissue degeneration, respectively, as well as an inability to grow and remodel. Tissue engineered heart valves (TEHVs) have been proposed to overcome these limitations by providing a scaffold that is designed to be gradually replaced by autologous functional tissue. As such, TEHVs should degrade at a rate matching new tissue formation to achieve proper function and avoid structural failure. Biodegradable polyurethane elastomers are suitable candidates for TEHVs and offer tunable degradability based on soft segment chemistry. Polyester soft segments in poly(ester urethane)urea (PEUU) generate faster degradation than polycarbonate soft segments in poly(carbonate urethane)urea (PCUU). These biodegradable polyurethanes can be electrospun into fully assembled, fibrous TEHVs. The objectives of this study were to evaluate the in vitro degradation profile of three polyurethane soft segment mixing strategies and the effects of a mechanically demanding environment on the degradation rate. Equal ratios of faster-degrading polyester and slower-degrading polycarbonate segments were mixed into polyurethanes using three strategies: 1) soft segment mixing during synthesis to form poly(ester carbonate urethane)urea, 2) physical blending of PEUU and PCUU polymers during solvation to form a single solution, and 3) electrospinning from two independent streams of PEUU and PCUU solutions. These mixing strategies varied the chemical composition of the polymer chains and electrospun fibers between groups. Electrospun TEHVs from each mixing strategy were subjected to accelerated degradation in a pulse duplicator with enzymatic solution for two weeks. Relative degradation rates were quantified based on scaffold mass and thickness loss, macro- and microscopic structural changes, and viscosity reduction. Additionally, biaxial mechanical compliance was monitored throughout degradation and initial scaffold blood compatibility was assessed. Soft segment mixed TEHVs had the most degradation while co-spun TEHVs degraded very little. Additionally, mechanical strength was maintained for each mixing strategy throughout degradation. Findings of this study are instrumental in efficiently designing TEHVs where tunable degradation is critical to match the in vivo tissue formation rate

Extraosseous Osteosarcoma of the Esophagus: A Case Report

Extraosseous osteosarcoma (EOO) is a malignant mesenchymal neoplasm that is located in the soft tissues without direct attachment to the skeletal system and that produces osteoid, bone, or chondroid material. EOO is an extremely rare disease, accounting for only 1% of soft tissue sarcomas, and typically presents in either an extremity or the retroperitoneum. This paper presents the case of a 45-year-old Caucasian male with extraosseous osteosarcoma of the esophagus

Fluorescence Bronchoscopic Surveillance in Patients With a History of Non-Small Cell Lung Cancer

Background Second lung primaries occur at a rate of 2% per patient per year after curative resection for non-small cell lung carcinoma (NSCLC). The aim of this study was to evaluate the role of fluorescence bronchoscopy using the Xillix® LIFE-Lung Fluorescent Endoscopy SystemTM (LIFE-Lung system) in the surveillance of patients for second NSCLC primaries after resection or curative photodynamic therapy (PDT)

Average outpouring velocity and flow rate of grains discharged from a tilted quasi-2D silo

The flow of granular materials through constricted openings is important in many natural and industrial processes. These complex flows - featuring dense, dissipative flow in the bulk but low-dissipation, low density outpouring in the vicinity of the orifice - have long been characterized empirically by the Beverloo rule and, recently, modeled successfully using energy balance. The dependence of flow rate on the silo's angle with respect to gravity, however, is not captured by current models. We experimentally investigate the role of tilt angle in this work using a quasi-2D monolayer of grains in a silo. We measure mass flow rate, the average exit velocities of grains, and the packing fraction along the orifice with varying tilt angles. We propose a model that describes our results (and earlier findings with 3D systems [H. G. Sheldon and D. J. Durian, Granul. Matter 12, 579 (2010)]) by considering the dependence of outpouring speed and angle with respect to the orifice angle and, importantly, the angle of stagnant zones adjacent to the orifice. We conclude by posing questions about possible extensions of our model in order to describe spatial variations of exit velocity and density along the orifice cross section.Comment: 10 pages and 11 figure

Pulmonary Embolism Following Laparoscopic Antireflux Surgery: A Case Report and Review of the Literature

Deep venous thrombosis and pulmonary embolism are concerning causes of morbidity and mortality in patients undergoing general surgical procedures. Laparoscopic surgery has gained rapid acceptance in the past several years and is now a commonly performed procedure by most general surgeons. Multiple anecdotal reports of pulmonary embolism following laparoscopic cholecystectomy have been reported, but the true incidence of deep venous thrombosis and pulmonary embolism in patients undergoing laparoscopic surgery is not known. We present a case of pulmonary embolism following laparoscopic repair of paraesophageal hernia. The literature is then reviewed regarding the incidence of pulmonary embolism following laparoscopic surgery, the mechanism of deep venous thrombosis formation, and the recommendations for deep venous thrombosis prophylaxis in patients undergoing laparoscopic procedures

Minimally invasive resection of benign esophageal tumors

ObjectiveBenign tumors of the esophagus are uncommon. Traditionally, resection has required thoracotomy or laparotomy. In this study we present our experience with resection of these tumors using a minimally invasive approach.MethodsA retrospective review of patients who underwent resection of benign esophageal tumors between 1990 and 2005 was conducted. Operative approach, tumor size, and outcomes after surgery were recorded.ResultsTwenty patients were identified (leiomyoma: n = 15; stromal tumor: n = 3; granular cell tumor, n = 1; schwannoma: n = 1). Four patients underwent an open approach (right thoracotomy); the remainder were resected using minimally invasive techniques (thoracoscopy, n = 9; laparoscopy, n =7). There were no postoperative leaks or other major complications after surgery. Two patients required repair of a mucosal injury during resection. Mean tumor size in the open group was 8.1 cm (range 7–10 cm) compared with 3.5 cm (range 0.9–8 cm) in the minimally invasive group. Median length of stay was 5.5 days in the open group compared with 2.75 days in the minimally invasive group. Five patients subsequently required fundoplication for worsening (n = 3) or new-onset (n = 2) gastroesophageal reflux disease after tumor resection.ConclusionsMinimally invasive resection of benign esophageal tumors is technically safe and associated with a shorter length of stay compared with open approaches. Although no specific cutoff for size could be identified, most tumors greater than 7 cm were removed by thoracotomy. The subsequent development of reflux may be related to the esophageal myotomy required for resection