Prosthetic valve leaflet perforation resulting in critical aortic insufficiency: A rare late complication after use of Cor-knot®.

The implementation of automatic fasteners such as the Cor-knot® device (LSI Solutions, Inc.) has revolutionized the field of minimally invasive valvular surgery. Nonetheless, paravalvular regurgitation, valvular embolization, and early leaflet perforation are all potential complications which may occur. Late manifestations of leaflet perforation (>5-year postimplantation) are rare. Herein, we discuss a patient who underwent remote Trifecta® (St. Jude, Inc.) surgical aortic valve replacement presenting with symptomatic critical aortic regurgitation secondary to leaflet perforation from automatically fastened metallic Cor-knot® sutures.

Synchronous Type 3 EVAR Endoleaks at Multiple Sites Following Transfemoral Transcatheter Aortic Valve Replacement.

We describe a complication following transfemoral transcatheter aortic valve replacement in a patient who underwent remote endovascular abdominal aortic aneurysm repair. This report highlights technical complications to be vigilant of when using intravascular catheterization in patients with previous aneurysm repair while also showcasing synchronous type 3 endoleaks at multiple sites. (Level of Difficulty: Advanced.).

Uninterrupted Continuation of VV-ECMO Without Anticoagulation for 44 Days in COVID-19 ARDS: A Precarious Quandary.

Venovenous extracorporeal membrane oxygenation (VV-ECMO) has become a mainstay treatment modality for a select patient population who do not respond to conventional medical therapy suffering from severe acute respiratory distress syndrome (ARDS) due to COVID-19. This therapy necessitates the utilization of anticoagulation, whether unfractionated heparin or bivalirudin, to prevent thrombotic complications. Scarce are reports of VV-ECMO implementation leading to acute hemorrhage mandating cessation of anticoagulation in a patient suffering from COVID-19 ARDS. Herein, the authors report a case of a successful outcome in a COVID-19 ARDS patient who suffered an acute hemorrhagic complication leading to pre-emptive termination of systemic anticoagulation. The authors believe this to be one of the first such cases in the literature.

Right Ventricular Failure Manifesting in Corona Virus Disease 2019 Acute Respiratory Distress Syndrome: A Call to Transition from Venovenous Extracorporeal Membranous Oxygenation to Right Ventricular Assist Device Extracorporeal Membranous Oxygenation.

Often labeled the forgotten ventricle, the right ventricle's (RV) importance has been magnified over the last 2 years as providers witnessed how severe acute respiratory syndrome coronavirus 2 infection has a predilection for exacerbating RV failure. Venovenous extracorporeal membranous oxygenation (VV-ECMO) has become a mainstay treatment modality for a select patient population suffering from severe COVID-19 acute respiratory distress syndrome. Concomitant early implementation of a right ventricular assist device with ECMO (RVAD-ECMO) may confer benefit in patient outcomes. The underlying mechanism of RV failure in COVID-19 has a multifactorial etiopathogenesis; nonetheless, clinical evaluation of a patient necessitating RV support remains unchanged. Herein, the authors report the case of a critically ill patient who was transitioned from a conventional VV-ECMO Medtronic Crescent cannula to RVAD-ECMO, with the insertion of the LivaNova ProtekDuo dual-lumen RVAD cannula.

Mobility of Yield Stress Fluids on Lubricant-Impregnated Surfaces.

A common problem which we encounter on a daily basis is dispensing of yield stress fluids such as condiments, lotions, toothpaste, etc. from containers. Beyond consumer products, assuring the flow of yield stress fluids such as crude oil, mud, blood, paint, pharmaceutical products, and others, is essential for the respective industries. Elimination of wall-induced friction can lead to significant savings in the energy required for flow of yield stress fluids, as well as associated product loss and cleaning costs. Lubricant-impregnated surfaces (LIS) have been shown to change the dynamic behavior of yield stress fluids and enable them to flow without shearing. Despite the wide applicability of this technology and its general appeal, the fundamental physics governing the flow of yield stress fluids on LIS have not yet been fully explained. In this work, we study the mobility of yield stress fluids on LIS, and explain the relationship between their macroscale flow behavior and the microscale properties of LIS. We show that for yield stress fluids the thermodynamic state of an LIS can be the difference between mobility and immobility. We demonstrate that LIS can induce mobility in yield stress fluids even below their yield stress allowing them to move as a plug without shearing with an infinite slip length. We identify different mobility mechanisms and establish a regime map for drag reduction in terms of the shear stress to yield stress ratio and the microscopic properties of the LIS. We demonstrate these regimes in a practical application of pipe flow thereby providing key insights for the design of LIS to induce mobility of yield stress fluids in a broad range of practical applications.

Synthetic Butterfly Scale Surfaces with Compliance-Tailored Anisotropic Drop Adhesion.

Many natural surfaces such as butterfly wings, beetles' backs, and rice leaves exhibit anisotropic liquid adhesion; this is of fundamental interest and is important to applications including self-cleaning surfaces, microfluidics, and phase change energy conversion. Researchers have sought to mimic the anisotropic adhesion of butterfly wings using rigid surface textures, though natural butterfly scales are sufficiently compliant to be deflected by capillary forces exerted by drops. Here, inspired by the flexible scales of the Morpho aega butterfly wing, synthetic surfaces coated with flexible carbon nanotube (CNT) microscales with anisotropic drop adhesion properties are fabricated. The curved CNT scales are fabricated by a strain-engineered chemical vapor deposition technique, giving ≈5000 scales of ≈10 µm thickness in a 1 cm2 area. Using various designed CNT scale arrays, it is demonstrated that the anisotropy of drop roll-off angle is influenced by the geometry, compliance, and hydrophobicity of the scales; and a maximum roll-off anisotropy of 6.2° is achieved. These findings are supported by a model that relates the adhesion anisotropy to the scale geometry, compliance, and wettability. The electrical conductivity and mechanical robustness of the CNTs, and the ability to fabricate complex multidirectional patterns, suggest further opportunities to create engineered synthetic scale surfaces.

Initial Outcomes of Symmetrically Flared Covered Nitinol Stents for Esophageal Pathologies.

BACKGROUND: A recently available, low profile, fully covered metal stent with symmetrical flares (FCMSF) may offer improved resistance to migration in esophageal disease. MATERIALS AND METHODS: A retrospective review of 58 esophageal FCMSF placed in 46 consecutive patients was performed. Pathologies included stricture and leak of benign and malignant etiology. RESULTS: Sixteen of 58 stents (28%) were placed urgently/emergently. All patients had successful stent deployment with 0% stent-related hospital mortality. Postoperative morbidity occurred in 15 of the 58 (26%) stents and included stent migration, atrial fibrillation, pneumonia, pneumothorax, urinary retention, hemodynamic instability, and chronic obstructive pulmonary disease exacerbation. In patients with stricture (n=29), mean dysphagia scores were reduced from 3.1±0.6 preoperatively to 1.1±0.8 postoperatively (P<0.001). For leak, stent therapy (±drainage) avoided formal esophageal operation in 95% (21/22). Four stents (6.9%) were removed for stent migration, 2 of which migrated after adjuvant chemoradiation. Adjuvant chemoradiation therapy was an independent risk factor for stent migration (odds ratio=1.6; P=0.02) by multivariable regression analysis. The mean duration of stent therapy was 65±62 days for stricture (27/34 remain in situ) and 57±57 days for leak (10/22 remain in situ). The median hospital length of stay was 2 days. CONCLUSIONS: FCMSF provide a safe and effective therapy for both benign and malignant esophageal dysphagia and leaks. The symmetrical property may contribute to the overall low observed migration rate while still allowing for simple and safe stent retrieval.

Treatment of recalcitrant subcutaneous emphysema using negative pressure wound therapy dressings.

Subcutaneous emphysema frequently occurs after pulmonary resection, but is usually mild and self-limiting. Patients can, however, develop severe symptomatic subcutaneous emphysema despite adequate thoracic drainage. There is a paucity of efficacious treatments for subcutaneous emphysema that does not respond to chest tube drainage. Previous reports have suggested that thoracoscopy may be an efficacious treatment, but is unfavourable due to the risks associated with reoperation. We present a case of a patient who developed severe subcutaneous emphysema after pulmonary lobectomy that was quickly and effectively treated using a commercially available negative pressure wound therapy dressing.

Drag reduction using lubricant-impregnated surfaces in viscous laminar flow.

Lubricant-impregnated surfaces (LIS), where micro/nanotextured surfaces are impregnated with lubricating liquids, have received significant attention for their robust, superslippery properties. In this study, we systematically demonstrate the potential for LIS to reduce drag in laminar flows. We present a scaling model that incorporates the viscosity of the lubricant and elucidates the dependence of drag reduction on the ratio of the viscosity of the working fluid to that of the lubricant. We experimentally validate this dependence in a cone and plate rheometer and demonstrate a drag reduction of 16% and slip length of 18 µm in the case where the ratio of working fluid viscosity to lubricant viscosity is 260.

Separating oil-water nanoemulsions using flux-enhanced hierarchical membranes.

Membranes that separate oil-water mixtures based on contrasting wetting properties have recently received significant attention. Separation of nanoemulsions, i.e. oil-water mixtures containing sub-micron droplets, still remains a key challenge. Tradeoffs between geometric constraints, high breakthrough pressure for selectivity, high flux, and mechanical durability make it challenging to design effective membranes. In this paper, we fabricate a hierarchical membrane by the phase inversion process that consists of a nanoporous separation skin layer supported by an integrated microporous layer. We demonstrate the separation of water-in-oil emulsions well below 1 µm in size. In addition, we tune the parameters of the hierarchical membrane fabrication to control the skin layer thickness and increase the total flux by a factor of four. These simple yet robust hierarchical membranes with engineered wetting characteristics show promise for large-scale, efficient separation systems.

Aortic endograft infection with aortoduodenal fistula associated with adjacent vertebral body mycobacterial osteomyelitis (Pott's disease).

Aortoenteric fistulas (AEFs) are a rare complication of infrarenal abdominal aortic aneurysm repair. They occur in <1% of aortic grafting procedures, result from graft defects, foreign bodies, and trauma, and are associated with a high mortality rate. We report a complex AEF associated with vertebral body osteomyelitis, likely secondary to tuberculous infection. A 78-year-old man presented with a 2-week history of abdominal pain, fever, and anemia. Past surgical history is significant for open repair of infrarenal abdominal aortic aneurysm followed later by an endovascular repair of a proximal para-anastomotic aneurysm. Computed tomography angiography revealed air in the aneurysm sac, without evidence of endoleak. The posterior aspect of the aneurysm was noted to be in continuity with a destructive osteomyelitis of the second lumbar vertebral body and an adjacent psoas abscess. Percutaneous drainage revealed purulent fluid containing mixed enteric flora. With fluoroscopic guidance, injection of contrast in the aortic sac drainage catheter demonstrated complex fistulous communications from the aortic sac to the overlying small intestine. After a course of drainage, antibiotic therapy, and parenteral nutrition, the patient underwent a transperitoneal repair of the AEF with duodeno-duodenectomy and wide debridement of the aortic sac and Dacron graft. Pathology revealed giant cell granulomas, highly suggestive of tuberculosis.

Minimally invasive valve surgery with antegrade perfusion strategy is not associated with increased neurologic complications.

BACKGROUND: A Society of Thoracic Surgeons' publication recently associated "minimally invasive" approaches with increased neurologic complications; this proposed association was questionable due to imprecise definitions. To critically reevaluate this issue, we reviewed a large minimally invasive valve experience with robust definitions. METHODS: From November 1995 to January 2007, 3,180 isolated, non-reoperative valve operations were performed; 1,452 (45.7%) were aortic replacements and 1,728 (54.3%) were mitral valve procedures. Surgical approach was standard sternotomy (28%) or minimally invasive technique (72%). Antegrade arterial perfusion was used in 2,646 (83.2%) patients and retrograde perfusion in 534 (16.8%). Aortic clamping was direct in 83.4%, with endoclamp in 16.4% and no clamp in 0.2%. Patients were prospectively followed in a proprietary database and the New York State Cardiac Surgery Reporting System (mandatory, government audited). A neurologic event was defined as a permanent deficit, a transient deficit greater than 24 hours, or a new lesion on cerebral imaging. RESULTS: Hospital mortality for aortic valve replacement was 4.0% (sternotomy [5.1%] versus minimally invasive [3.4%] p = 0.13); for mitral procedures it was 2.4% (sternotomy [4.8%] versus minimally invasive [1.8%] p = 0.001). Multivariate analysis revealed that age, female gender, renal disease, ejection fraction less than 0.30, chronic obstructive pulmonary disease, and emergent operation were risk factors for mortality. Stroke occurred in 71 patients (2.2%) (sternotomy [2.1%] versus minimally invasive [2.3%] p = 0.82). Multivariate analysis of neurologic events revealed that cerebrovascular disease, emergency procedure, no-clamp, and retrograde perfusion were risk factors. In patients 50 years old or younger (n = 662), retrograde perfusion had no significant impact on neurologic events (1.6% vs 1.1%, p = 0.57). CONCLUSIONS: A minimally invasive approach with antegrade perfusion does not result in increased neurologic complications. Retrograde perfusion, however, is associated with increased neurologic risk in older patients.

Simulating video-assisted thoracoscopic lobectomy: a virtual reality cognitive task simulation.

OBJECTIVE: Current video-assisted thoracoscopic surgery training models rely on animals or mannequins to teach procedural skills. These approaches lack inherent teaching/testing capability and are limited by cost, anatomic variations, and single use. In response, we hypothesized that video-assisted thoracoscopic surgery right upper lobe resection could be simulated in a virtual reality environment with commercial software. METHODS: An anatomy explorer (Maya [Autodesk Inc, San Rafael, Calif] models of the chest and hilar structures) and simulation engine were adapted. Design goals included freedom of port placement, incorporation of well-known anatomic variants, teaching and testing modes, haptic feedback for the dissection, ability to perform the anatomic divisions, and a portable platform. RESULTS: Preexisting commercial models did not provide sufficient surgical detail, and extensive modeling modifications were required. Video-assisted thoracoscopic surgery right upper lobe resection simulation is initiated with a random vein and artery variation. The trainee proceeds in a teaching or testing mode. A knowledge database currently includes 13 anatomic identifications and 20 high-yield lung cancer learning points. The "patient" is presented in the left lateral decubitus position. After initial camera port placement, the endoscopic view is displayed and the thoracoscope is manipulated via the haptic device. The thoracoscope port can be relocated; additional ports are placed using an external "operating room" view. Unrestricted endoscopic exploration of the thorax is allowed. An endo-dissector tool allows for hilar dissection, and a virtual stapling device divides structures. The trainee's performance is reported. CONCLUSIONS: A virtual reality cognitive task simulation can overcome the deficiencies of existing training models. Performance scoring is being validated as we assess this simulator for cognitive and technical surgical education.

Extended cardiac resection for obstructing pseudotumor due to Ormond disease.

A 60-year-old man presented with symptoms from an intracardiac mass. His medical history included retroperitoneal fibrosis (Ormond disease). Magnetic resonance imaging revealed an obstructing bilobular mass in the right atrium, located at the caval junction and extending intramurally into the atria, septum, and right ventricle. En bloc resection of the right atrium, interatrial septum, dome of the left atrium, vena cava, anterior tricuspid annulus, right coronary artery, and partial right ventriculectomy was completed with right ventricular repair, tricuspid valve replacement, and left and right atrial replacement with bovine pericardium. This lesion was a myofibroblastic tumor with the same histologic features as his retroperitoneal fibrosis.

Polyoma virus hemorrhagic cystitis in an otherwise normal child.

We describe a case of polyoma virus hemorrhagic cystitis in a nonimmunosuppressed child. Polyoma virus infection was suspected because of abnormal urine cytology. Polyoma virus cystitis in nonimmunosuppressed children is self-limited, resolving spontaneously within 2 weeks.

Enhancing stability and expression of recombinant human hemoglobin in E. coli: Progress in the development of a recombinant HBOC source.

The commercial feasibility of recombinant human Hb (rHb) as an O(2) delivery pharmaceutical is limited by the production yield of holoprotein in E. coli. Currently the production of rHb is not cost effective for use as a source in the development of third and fourth generation Hb-based oxygen carriers (HBOCs). The major problems appear to be aggregation and degradation of apoglobin at the nominal expression temperatures, 28-37 degrees C, and the limited amount of free heme that is available for holohemoglobin assembly. One approach to solve the first problem is to inhibit apoglobin precipitation by a comparative mutagenesis strategy to improve apoglobin stability. alpha Gly15 to Ala and beta Gly16 to Ala mutations have been constructed to increase the stability of the alpha helices of both subunits of HbA, based on comparison with the sequences of the more stable sperm whale hemoglobin subunits. Fetal hemoglobin is also known to be more stable than human HbA, and sequence comparisons between human beta and gamma (fetal Hb) chains indicate several substitutions that stabilize the alpha1beta1 interface, one of which, beta His116 to Ile, increases resistance to denaturation and enhances expression in E. coli. These favorable effects of enhanced globin stability can be augmented by co-expression of bacterial membrane heme transport systems to increase the rate and extent of heme uptake through the bacterial cell membranes. The combination of increased apoglobin stability and active heme transport appear to enhance holohemoglobin production to levels that may make rHb a plausible starting material for all extracellular Hb-based oxygen carriers.