Types Of Conduits Research Articles

COMPARATIVE ANALYSIS OF PULMONARY ARTERY CONDUITS IN CHILDREN

HighlightsThe review presents the analysis of long-term outcomes of implantation of the most common types of conduits in children. Predictors of the development of dysfunction and infective endocarditis are presented. Aim. To analyze the function of the available types of conduits in pediatric group of patients who underwent right ventricular outflow tract (RVOT) reconstruction.Methods. The retrospective study included patients between 0 and 18 years old who underwent RVOT reconstruction using conduits between 2000 and 2017. Clinical records and imaging data were analyzed.Results. A total of 400 patients underwent implantation of 495 conduits including glutaraldehyde (GA)-treated bovine jugular vein (contegra) (n = 181); GA-treated xenopericardial conduit (BioLAB) (n = 84); diepoxyde (DE)-treated xenopericardial conduit with porcine aortic root (AB-composite) (n = 65); DE-treated xenopericardial conduit (Pilon) (n = 32) and cryopreserved pulmonary homograft (n = 135). Primary implantation was made in 383 cases (77.3%) and conduit reimplantation was made in 112 cases (22.5%). Median follow-up was 79.9 (42.6; 110.7) months. Redo surgery with conduit replacement was made in 41 (8.5%) cases, of these, 6 (2.1%) conduits were replaced due to thrombosis, endocarditis was diagnosed in 14 patients (4.8%), there were no statistical differences between the groups. Younger age was associated with high risk of early dysfunction (OR 0.97; 95% CI 0.96–0.99, p = 0.03). Multivariate analysis revealed that the type of conduit was not a risk factor (OR 0,86; 95% CI 0,64–1,15; p = 0,64). Severe calcification was the main predictor of conduit-associated mortality (OR 0.02; 95% CI 0.002–0.34; p = 0.005).Conclusion. Incidence of reintervention due to conduit dysfunction is still high in pediatric group and is not associated with type of conduit. All types of available conduits showed comparable rates of dysfunction. Risk of developing conduit-associated infective endocarditis also does not depend on the type of implanted graft.

Application of right ventricular to pulmonary valved conduit in the surgical treatment of congenital heart disease.

Pulmonary valve replacement and right ventricular outflow tract reconstruction with valved conduits have been the shortcomings of paediatric cardiac surgeons in the treatment of CHD. In recent decades, encouraging achievements have been made in right ventricular outflow tract technology. Since Klinner reported the first right ventricle-to-pulmonary artery connection using unvalved conduits made of autologous pericardium in 1964, various right ventricle-to-pulmonary artery conduits have gradually been used in the treatment of various complex CHD. Compared with other materials, valved homograft conduit (VHC) is more consistent with physiological characteristics, better haemodynamics, easy suture and good haemostasis, anti-calcification, anti-infection, and without the need for lifelong anticoagulation, which makes VHC the best material for reconstruction of right ventricular outflow tract. However, due to the shortage of donor sources, other alternative conduits such as polytetrafuoroethylene valved conduits have been developed, and the results are not inferior to VHC in clinical application. The emerging tissue engineering technology is expected to utilise recipient-derived endothelial cells for implantation onto the decellularized VHC or degradable synthetic materials in order to construct a recipient-specific tissue-engineered valved conduit. This advancement holds great potential as an ideal biological transplant material and valve replacement for CHD. It will completely solve the problems of immune rejection and the growth of the conduit that cannot adapt to the physical growth of children. This review provides a comprehensive review of the clinical indications for right ventricle-to-pulmonary artery conduits application, optimal timing for surgery, current practices in utilising various types of external conduits, and considerations for re-replacement.

Comparative analysis of the efficiency of the use of various types of conduits during coronary artery bypass grafting

The OBJECTIVE was to compare efficiency of the use of various types of conduits during coronary artery bypass grafting (CABG).METHODS AND MATERIALS. The retrospective study included 282 patients, who underwent CABG, performed with different types of conduits. The average age of the patients was 63.2±8.5 years; the majority of 231 patients (81.9%) were male. Patients were separated in 3groups depending on the use of conduits: the first one included patients after bimammary coronary artery bypass grafting (n=77); the second one involved coronary artery bypass grafting using radial artery(n=87); the third one included patients with venous conduits (n=77). The main endpoint of the study was the development of conduit dysfunctions in the long-term period according to diagnostic coronary artery bypass grafting.RESULTS. The average follow-up time in the long-term period was 44.9±39 months. During this period, 198 patients underwent diagnostic coronary artery bypass grafting. According to the results of the analysis, the greatest effectiveness was observed in groups using arterial conduits – the left internal thoracic artery and radial artery. For example, the incidence of dysfunction of the left internal thoracic artery in the anterior artery basin was 8.2%; the incidence of dysfunction of radial artery in the right artery basin was 12.5 %, and in the obtuse marginal branch basin – 11.5 %; while the incidence of venous conduits’ dysfunction varied, reaching its maximum of 42.8 %.CONCLUSIONS. Thus, the greatest efficiency was observed when using the left and the right internal thoracic arteries, thereafter by the radial artery. The results of using venous conduits were lower.

Gastric conduit reconstruction after esophagectomy.

A high risk of complications still accompanies gastric conduit reconstruction after esophagectomy. In this narrative review, we summarize the technological progress and the problems of gastric conduit reconstruction after esophagectomy. Several types of gastric conduits exist, including the whole stomach and the narrow gastric tube. The clinical outcomes are similar between the two types of conduits. Sufficient blood supply to the conduit is mandatory for a successful esophageal reconstruction. Recently, due to the availability of equipment and its convenience, indocyanine green angiography has been rapidly spreading. When the blood perfusion of the planning anastomotic site is insufficient, several techniques, such as the Kocher maneuver, pedunculated gastric tube with duodenal transection, and additional microvascular anastomosis, exist to decrease the risk of anastomotic failure. There are two different anastomotic sites, cervical and thoracic, and mainly two reconstructive routes, retrosternal and posterior mediastinal routes. Meta-analyses showed no significant difference in outcomes between the anastomotic sites as well as the reconstructive routes. Anastomotic techniques include hand-sewn, circular, and linear stapling. Anastomoses using linear stapling is advantageous in decreasing anastomosis-related complications. Arteriosclerosis and poorly controlled diabetes are the risk factors for anastomotic leakage, while a narrow upper mediastinal space and a damaged stomach predict leakage. Although standardization among the institutional team members is essential to decrease anastomotic complications, surgeons should learn several technical options for predictable or unpredictable intraoperative situations.

Origin of Fracture-Controlled Conduits in Calcite-Rich Highly Productive Aquifers Impregnated with Diagenetic Silica

The origin of highly permeable flow paths in carbonate-siliciclastic rocks, such as large-aperture fractures in aquifers in the Eastern Bohemian Cretaceous Basin (EBCB), is poorly understood. The karst potential was assessed from the rock carbonate content and the degree of disintegration after leaching in HCl. Surprisingly, dissolution of calcite in EBCB usually did not lead to rock disintegration until calcite > 78%. Instead, porosity increased significantly. High-porosity rock is held together by microns-thick secondary silica cement with a foam-like structure and considerable tensile strength. Three types of conduits occur in the EBCB: (i) bedding-parallel conduits associated with calcite-rich layers, (ii) subvertical fracture swarm conduits that develop on damaged zones of fracture swarms, and (iii) conduits formed by dissolution of calcite veins by groundwater flow. These are ghost-rock karst features where calcite is leached from the rock in the first phase and the residue is washed out by conduits under steep hydraulic gradients in the second phase. Very similar features have been described in Minnesota and Wisconsin, USA. Research has shown that fractures with sharp-edged walls that give the impression of an extensional tectonics origin may actually be ghost-rock karst features in which dissolution and piping have played an important role in their enlargement.

Two-dimensional high-resolution numerical investigation of eddy effect in artificial rough conduits with different shapes

Subsurface conduit flow is a critical element of investigating groundwater movement in karst regions, and it is still poorly understood due to complexity of subsurface conduit geometries and the nonlinearity of the conduit flux-hydraulic gradient relationship. A significant nature of the flow nonlinearity is the occurrence of different eddies in conduits. To reveal the nonlinear nature of conduit flow, this study investigates the influence of the eddy effect on the hydraulic gradient of different rough conduits based on extensive high-fidelity numerical simulations. Overall, the hydraulic gradients of all types of rough conduits show quadratic relations with an increase in the specific discharge. In addition, the triangular rough conduit has the largest hydraulic gradient, which gradually decreases as the shape coefficient (which is used to quantify rough elements) increases. We have identified the development and evolution of eddies in different types of rough conduits in detail. This study shows that a larger specific discharge leads to a larger eddy area, and the hydraulic gradient changes exponentially with the eddy area ratio within a limited range. Finally, the relationships among specific discharges, eddy area ratio, and hydraulic gradients are constructed and summarized. The results of this investigation are helpful for developing realistic karst groundwater flow and transport models in which subsurface conduit plays a dominant role for conducting groundwater flux and mass transport.

Comparative evaluation of different types of gastric conduits used for single-stage reconstruction during oesophageal cancer esophagectomy. Review

In the treatment of local and local‑regional oesophageal cancer, esophagectomy takes centre stage. It is a complex procedure with a high rate of postoperative complications. There are different methods for oesophageal reconstruction, including colon interposition, supercharged jejunal interposition, and gastric pull‑up. Each has both advantages and disadvantages. However, a gastric graft is the preferred option due to the less traumatic nature of the operation. Currently, there are different methods for forming a gastric graft. Gastric conduits are classified based on their shape and can be categorised as whole‑stomach, sub‑total stomach, or gastric tube. Previous research on the functional characteristics of gastric conduits revealed that the most effective solution is a typical gastric tube. Due to its width (3—6 cm), the gastric tube limits its impact on lung movement within the pleural cavity, hence decreasing the incidence of postoperative respiratory complications (e.g., pneumonia). Pulmonary complications and anastomotic leaks are the main contributing causes of postoperative morbidity and mortality after esophagectomy. Other complications include technical and functional issues, as well as delayed problems such as anastomotic strictures and disease recurrence. However, the rate of complications remains between 20 and 80%, prompting oncologic surgeons to develop new methods for gastric conduit formation. Over the past 5 years, innovative methods using a special‑shaped gastric tube have been suggested. They appear to decrease the incidence of postoperative complications and enhance nutritional outcomes. This study aimed to evaluate the advantages of using special‑shaped gastric tubes in clinical practice as opposed to whole‑stomach and typical gastric tubes.

20-Year follow-up and comparison of valved conduits used for right ventricular outflow tract reconstruction: single-centre, propensity score match analysis.

Surgical repair of complex congenital heart defects with hypoplasia or atresia of the right ventricular outflow tract (RVOT) may require pulmonary valve implantation or replacement during the primary repair or reoperation. The purpose of this study is to evaluate the outcomes of cryopreserved homografts, bovine jugular vein conduits and decellularized Matrix P Plus N conduits in patients undergoing RVOT reconstruction at a single centre. Retrospective, single-centre review of 173 patients with 199 conduits undergoing right ventricle-to-pulmonary artery reconstruction with valved conduit from 2002 to 2022. A total of 199 conduits were implanted in 173 patients (62.8% male), with a mean age of 8.97 ± 8.5 years. The following 3 types of conduits were used: homografts 129 (64.8%), bovine jugular vein conduits 45 (22.7%) and Matrix P Plus N 25 (12.5%). During the mean follow-up duration of 8.6 ± 5.8 years, there were 20 deaths, 35 conduit reoperations and 44 catheter reinterventions. Overall survival, reoperation-free and catheter reintervention-free survival at 20 years were 83%, 67.8% and 65.6%, respectively. Multivariable Cox analysis identified younger patient age, smaller conduit size, low patient weight and primary diagnosis of common arterial trunk as risk factors for reoperation and catheter reintervention. Long-term outcomes of reconstruction of the RVOT using homografts, bovine jugular vein and Matrix P Plus N conduits were acceptable. The reoperation rate for conduit dysfunction did not differ significantly among groups. Over time, the need for conduit replacement was higher in smaller conduits and in patients with common arterial trunk diagnosis.

Treatment methods for peripheral nerve injuries (a literature review)

Aim: to analyze modern professional literature and summarize data on treatment methods for peripheral nerve injuries, taking into account the mechanisms of positive effects. The article presents an overview of possible methods for treatment of peripheral nerve injuries, fundamental classifications of peripheral nerve injuries, their differences are considered, pathophysiological mechanisms and the probability of spontaneous recovery depending on the degree of injury, general principles and conditions for successful regeneration of the peripheral nerve. Options, combinations, advantages and disadvantages of such surgical methods for peripheral nerve injury treatment as neurorrhaphy, autotransplantation and allotransplantation are described in detail, such terms as “small”, “large” and “critical” gaps between the nerve stumps are specified. Classifications and characteristics of conduits are described, types of synthetic conduits are considered. The use of drugs, Schwann cells, growth and neurotrophic factors, neural, embryonic and mesenchymal stem cells of various origins, exosomes of mesenchymal stem cells in the so-called “stem cell-free therapy” in treating this pathology is mentioned. Genetically modified mesenchymal stem cells, optokinetics are also noted, such physical methods for peripheral nerve injury treatment as short-term low-frequency electrical stimulation of the nerve, magnetic stimulation, low-intensity ultrasound, photobiomodulation therapy, photochemical bonding are discussed, indicating some mechanisms of their positive effects. Conclusions. Improving the quality of life and reducing the degree of disability in patients with injuries of the main nerve trunks depends on the combined use of a number of surgical, bioengineering and regenerative technologies. These involve the restoration of the anatomical continuity of the nerve, including through the use of natural or artificial elements, cellular technologies and the management of regenerative processes. Therefore, every time, a surgeon is facing a major challenge to create a combination of various means from the indicated basic components for the treatment of nerve damage in managing a particular patient. However, such a treatment approach requires proper competences of surgeons as well as specific material and technical bases in order to bring down the level of social tension in patients with injuries of the main nerve trunks.

Conduits and Strategies for Arterial Revascularization in CABG.

Ischemic heart disease is the leading cause of death in the United States. Depending on the severity of the coronary artery disease, treatment options include percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG). Although CABG has been performed since the 1970s, there is still debate onwhich conduit to use after the left internal thoracic artery. Currently, national registries report the left internal thoracic artery and the saphenous vein as the most commonly used conduits in CABG, while other arterial grafts, such as the radial artery, represent a minority, even though the current evidence suggests potential benefits of these arterial conduits. In this review, we aimed to describe the different types of arterial conduits used for CABG and summarize the evidence behind their use.

Advances in Large Gap Peripheral Nerve Injury Repair and Regeneration with Bridging Nerve Guidance Conduits.

Peripheral nerve injury is a common complication of accidents and diseases. The traditional autologous nerve graft approach remains the gold standard for the treatment of nerve injuries. While sources of autologous nerve grafts are very limited and difficult to obtain. Nerve guidance conduits have been widely used in the treatment of peripheral nerve injuries as an alternative to nerve autografts and allografts. However, the development of nerve conduits does not meet the needs of large gap peripheral nerve injury. Functional nerve conduits can provide a good microenvironment for axon elongation and myelin regeneration. In this review, we summarize the manufacturing methods and different design types of functional bridging nerve conduits for nerve conduits combined with electrical or magnetic stimulation and loaded with Schwann cells, etc. It summarizes the literature and finds that the technical solutions of functional nerve conduits with electrical stimulation, magnetic stimulation and nerve conduits combined with Schwann cells can be used as effective strategies for bridging large gap nerve injury and provide an effective way for the study of large gap nerve injury repair. In addition, functional nerve conduits provide a new way to construct delivery systems for drugs and growth factors in vivo. This article is protected by copyright. All rights reserved.

4D printed tri-segment nerve conduit using zein gel as the ink for repair of rat sciatic nerve large defect

Zein has enormous potential for application in biomedical field due to biodegradation and biocompatibility, we have recently prepared zein gel as a possible 3D printing ink. Our previous studies found that the pore structure in zein material can reduce early inflammation, promote the polarization of macrophages toward the M2 phenotype, and accelerate nerve regeneration. To further explore the role of zein in nerve repair, we used 4D printing technique to create nerve conduits with zein protein gel, and designed 2 types of tri-segment conduits with different degradation rates. Structural parts printed in support baths with higher water content show faster degradation rates than those printed in support baths with lower water content. The conduits that degraded quickly at both ends and slowly in the middle (CB75-CB40-CB75) and the conduits that degraded slowly at both ends and quickly in the middle (CB40-CB75-CB40) were 4D printed, respectively. Animal experiments suggest that the CB75-CB40-CB75 conduit is better for nerve repair, which may be because its degradation pattern can match to the pattern of nerve regeneration better. Our new strategy through 4D printing indicated that fine modulation in conduit degradation can affect efficacy of nerve repair significantly.

Survival and Independent Predictors of Mortality Following Coronary Artery Bypass Graft Surgery in a Single-Unit Practice in the United Kingdom Over 20 Years

The types of graft conduits and surgical techniques may impact the long-term outcomes of patients after coronary artery bypass graft (CABG) revascularization. This study observed a long-term survival rate following CABG surgery over 20 years in the United Kingdom. A total of 2979 isolated CABG patients were studied from 1999 to 2020, and postoperative data were obtained from the hospital-recorded mortality by the data quality team of the information department. Postdischarge survival was estimated using the Kaplan-Meier method, and statistical significance was obtained with log-rank tests and the Gehan-Breslow test, and the Holm-Sidak method was used for multiple pairwise comparisons. The study observed male predominance (80%), and the median age was statistically significant (P <0.001) among the groups, 66 years (interquartile range 58-73) and 72 years (interquartile range 66-78) in survivor and non-survivor groups, respectively. In the Holm-Sidak method analysis, the best survival rate (mean 18.7 years) was observed in the total arterial group with significantly decreased survival for the mixed arterial and venous group (mean 16.12 years) and only the vein group (10.44 years). The Cox regression model observed that the New York Heart Association (NYHA) class III-IV (HR 1.57), chest re-exploration (HR 2.14), preoperative dialysis (HR 3.13), and redo surgery (HR 3.04) were potential predictors of the postoperative mortality (P ≤0.05). In our series over 20 years, albeit off-pump and on-pump CABG observed similar survival rates, the total arterial myocardial revascularization population has significantly better long-term survival benefits.

Venous Reconstruction in Extremity Soft Tissue Sarcoma Is Not Essential.

Limb salvage is an important concern following complete oncologic resection for extremity soft tissue sarcoma (STS). Vascular reconstruction is essential for limb salvage. The purpose of this study was to evaluate the outcomes of vascular reconstruction in patients with extremity STS. This is a retrospective, multi-center, case series of consecutive patients who underwent vascular reconstruction during extremity STS resection at 2 major centers in Korea. Demographics, reconstruction methods, type of conduit, surgical complications, graft patency, limb salvage rate, and patient survival were reviewed. From March 2005 to December 2020, 43 patients underwent vascular reconstructions during STS resection. Among the patients, 22 (51.2%) received arterial only, and 21 (48.8%) received simultaneous arterial and venous reconstructions. For the types of conduits, autologous saphenous veins (56.2%), artificial grafts (26.3%), and cryopreserved allografts (15.8%) were used. During a median follow-up of 23.8 months (interquartile range; 7.7-54.5), the overall primary patency of the reconstructed vessels was significantly higher in arteries than in veins (82.5% vs 56.3% at 12 months, P < .001). According to the type of conduit, the primary patency rate of autogenous vein seemed higher in venous reconstruction, however, there was no statistical significance in both arterial and venous reconstruction. There was no significant difference in primary arterial patency rate (P = .132) or incidence of surgical complications including postoperative edema or wound problem whether or not simultaneous venous reconstruction was performed with arterial reconstruction. The overall limb salvage rate and patient survival were 97.4%, 95.1%, and 89.4% and 91.9%, 81.7%, and 65.4% at 12, 24, and 36 months, respectively. Patency rates were poorer in venous reconstruction than in arterial reconstruction. In terms of arterial patency and postoperative complication, the role of simultaneous arterial and venous reconstruction seems not essential, however, it needs to be evaluated in future studies.

Assessment of Human Epineural Conduit of Different Size Diameters on Efficacy of Nerve Regeneration and Functional Outcomes.

Different types of nerve conduits are used to bridge peripheral nerve gaps when a tension-free repair is unattainable. To best support nerve regeneration, naturally occurring conduits have been tested. Since allografts offer an unlimited source of epineurium, we have developed human epineural conduit (hEC) as a novel technology to bridge nerve gaps. Considering acellular properties, and lack of immunogenic response, epineurium-derived conduits represent an attractive material, when compared with nerve allografts that require systemic immunosuppression. In this study, we introduce the hEC as a novel naturally occurring material applied for repair of nerve gaps after trauma. We tested the application of hEC created from human sciatic nerve in the restoration of 20 mm sciatic nerve defects in the nude rat model. Four experimental groups were studied: group 1: no repair control (n = 6), group 2: autograft control (n = 6), group 3: matched diameter hEC (n = 6), and group 4: large diameter hEC (n = 6). Functional tests of toe-spread and pin prick were performed at 1, 3, 6, 9, 12 weeks after repair. At 12 weeks, nerve samples were collected for immunostaining of Laminin B, S-100, glial fibrillary acidic protein (GFAP), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), von Willebrand factor, and histomorphometric analysis of myelin thickness, axonal density, fiber diameter, and percentage of the myelinated nerve fibers. Muscle samples were gathered for gastrocnemius muscle index (GMI) and muscle fiber area ratio measurements. Best functional recovery, as well as GMI, was revealed for the autograft group, and was comparable to the matched hEC group. Significant differences were revealed between matched and large hEC groups in expression of S100 (p = 0.0423), NGF (p = 0.269), VEGF (p = 0.0003) as well as in percentage of myelinated fibers (p < 0.001) and axonal density (p = 0.0003). We established the feasibility of hEC creation. The innovative method introduces an alternative technique to autograft repair of nerve defects.

A Comparison of Different Types of Esophageal Reconstructions: A Systematic Review and Network Meta-Analysis.

Background: A total esophagectomy with gastric tube reconstruction is the mainstream procedure for esophageal cancer. Colon interposition and free jejunal flap for esophageal reconstruction are the alternative choices when the gastric tube is not available. However, to date, a solution for the high anastomosis leakage rates among these three types of conduits has not been reported. The aim of this network meta-analysis was to investigate the rate of anastomotic leakage (AL) among the three procedures to determine the best esophageal substitute or the future direction for improving the conventional gastric pull-up (GPU). Methods: We searched PubMed, Cochrane, and Embase databases. We included esophageal cancer patients receiving esophagectomy and excluded patients with other cancer. The random effect model was used in this network meta-analysis. The Newcastle–Ottawa Scale (NOS) was used for the quality assessment of studies in the network meta-analysis, and funnel plots were used to evaluate publication bias. The primary outcome is anastomosis leakage; the secondary outcomes are stricture formation, length of hospital stays, and mortality rate. Results: Nine studies involving 1613 patients were included in this network meta-analysis. The trend results indicated the following. Regarding anastomosis leakage, free jejunal flap was the better procedure; regarding stricture formation, colon interposition was the better procedure; regarding mortality rate, free jejunal flap was the better procedure; regarding length of hospital stay, gastric pull-up was the better treatment. Discussion: Overall, if technically accessible, free jejunal flap is a better choice than colon interposition when gastric conduit cannot be used, but further study should be conducted to compare groups with equal supercharged patients. In addition, jejunal flap (JF) cannot replace traditional gastric pull-up (GPU) due to technical complexities, more anastomotic sites, and longer operation times. However, the GPU method with the supercharged procedure would be a possible solution to lower postoperative AL. The limitation of this meta-analysis is that the number of articles included was low; we aim to update the result when new data are available. Funding: None. Registration: N/A.

Long-Term Follow-Up of Right Ventricle to Pulmonary Artery Biologic Valved Conduits Used in Pediatric Congenital Heart Surgery

Valved conduit reconstruction between the right ventricle (RV) and the pulmonary circulation is often necessary in the surgical treatment of complex congenital heart defects. The aim of this study is to evaluate the long-term performance of the three types of conduits we have used and assess risk factors for conduit failure. Retrospective, single-center review of 455 consecutive pediatric patients with 625 conduits from 1990 to 2019 undergoing RV-to-pulmonary artery (PA) reconstruction with a valved conduit. The three conduit types investigated were pulmonary homograft, aorta homograft, and bovine jugular vein (BJV) graft. Overall patient survival was 91.4%, freedom from conduit replacement (FCR) was 47.4%, and freedom from reintervention (FFR) was 37.8% with a median follow-up of 8.7 years (interquartile range 4.3–13.3 years). For pulmonary homografts, 10-, 20-, and 28-year FCR was 79.6%, 68.6%, and 66.0%, respectively. For aortic homografts, 10-, 20-, and 30-year FCR was 49.8%, 31.5%, and 23.0%, respectively. For BJV grafts, 10- and 19-year FCR was 68.1% and 46.0%, respectively. When controlling for baseline variables, FCR was similar for pulmonary homografts and BJV grafts. Overall patient survival was excellent. Risk factors for conduit failure in patients operated with reconstruction of the RV-PA outflow tract included low age, low weight, small conduit size, and certain cardiac diagnoses. There was no evidence for a shorter life span of the second graft. Pulmonary homografts and BJV grafts performed similarly but the risk of endocarditis was greater in the BJV group.

Off-Pump Coronary Artery Bypass Graft Surgery with Bilateral Internal Mammary Arteries in Left Main Coronary Artery Disease. Is There Any Benefit in 10-Year Mortality?

Background: The randomized controlled trials comparing coronary artery bypass graft (CABG) surgery versus percutaneous coronary intervention (PCI) included all types of surgical techniques (on-pump and off-pump) and different conduits (arterial and venous). Is it reasonable to assume that all surgical techniques are equal in terms of late mortality? Objectives: The aim of this study was to evaluate whether off-pump CABG surgery using both mammary arteries provides additional benefit over conventional revascularization using single mammary artery in terms of long-term survival for left main coronary artery (LMCA) disease. Methods: We conducted a retrospective, observational and comparative study (n=723) adjusted for risk. A stratified analysis was performed according to the use of single internal thoracic artery (SITA, n=144) or bilateral internal thoracic arteries (BITA, n=579) analyzing survival at 10 years after the intervention. Results: Survival at 10 years was significantly higher in BITA group (79.0%±3.4% vs 67.0%±4.9%, log-rank test, p &lt;0.01). This advantage was also observed in the risk-adjusted analysis (93.0%±4.6 vs 69.0%±5.7 respectively, p=0.03). The use of BITA was an independent predictor of 10-year survival (HR 0.57, 95% CI 0.37-0.87, p=0.01). Conclusion: The use of bilateral internal mammary arteries in patients with left main coronary artery disease undergoing off-pump coronary artery bypass grafting was associated with higher survival at 10 years.

Physics Augmented Correlations and Machine Learning Methods to Accurately Calculate Dead Oil Viscosity Based on the Available Inputs

Summary Viscosity is one of the key parameters that is necessary to describe the fluid flow and pressure propagation in porous media as well as flow in pipes and various types of conduits. In this study, we have developed two different approaches to be able to estimate the viscosity seamlessly from a fraction to a million centipoise range. Our first approach was based on a trainable explicit expression that uses a reference viscosity measured at any temperature. This is a very common situation as the viscosity may have already been measured at reservoir temperature. Using the reference viscosity concept for many data sets, we also demonstrated the validity and tuneability of the proposed approach to predict the viscosities for the entire temperature range of interest. Our second method is developed for the cases that we did not have any viscosity measurements or no valid viscosity measurements. For such circumstances, we have utilized the extreme gradient boost (XGB) method algorithm (XGB Method) (Friedman 2001; Chen et al. 2015) using leave-one-out cross-validation (LOOCV) (Shao 1993), to be able to estimate the viscosity for the entire range of viscosities that are encountered for crudes. Some of the details of hybrid methods and other regression/machine learning methods and the role of the asphaltenes are already discussed by Sinha et al. (2019, 2020). The current approach uses a richer data set than any of the published papers with very limited input parameters: reservoir temperature, API gravity, and molecular weight, and the tuneability of the models is constrained with the molecular weight of the crudes.

Geological, geophysical, and geochemical characteristics of deep-routed fluid seepage and its indication of gas hydrate occurrence in the Beikang Basin, Southern South China Sea

Deep-routed fluid seepage conduits are widely distributed in the Southern South China Sea (SSCS), and gas hydrates have been discovered inside these conduits through drilling and logging. Due to a lack of integrated geological, geophysical, and geochemical data, deep-routed fluid seepage conduits and their relationship to gas hydrate occurrence are still unclear. In this study, a comprehensive investigation of fluid seepage was conducted through systematic analysis of high-resolution 2-D seismic data, multibeam bathymetry data, headspace gas and carbon isotope components, authigenic carbonates, pore water, biomarkers, and hydrate phase equilibrium simulation. Multiple types of deep-routed conduits—which typically manifested as mud volcanoes, diapirs, fluid-escape pipes, and paleo-uplift associated faults—were identified. These manifestations were generally accompanied by Bottom Simulating Reflectors (BSRs), blanking zones, locally enhanced reflections, "pulled-up" reflections, pockmarks, mounds, and gas plumes, which indicated fluid seepage and possible gas hydrate accumulation. The Sulfate Methane Transition Zone (SMTZ) in the fluid seepage sites occurred at relatively shallow depths of 325–660 cmbsf (centimeter below the seafloor), suggesting a high methane flux and sufficient gas supply. The carbon isotope composition of the methane (−92.6‰ < δ13C < −50.2‰) and the detection of ethane, propane, and n-butane, as well as multiple geological configuration biomarkers, all indicate that deep-sourced hydrocarbons and thermogenic gas have migrated into the shallow layer through deep-routed conduits. Several geological and geochemical anomalies, including gas expansion, gas bubbling in piston core sediments, negative pore water chloride anomalies, and δ18O enrichment (3.8‰ < δ18O < 4.1‰) in the cold seep carbonates, provide evidence of hydrate dissociation during core recovery. The deep-routed fluid seepage and the accompanying hydrocarbon gas supply have a significant influence on the potential thermogenic gas-sourced hydrate accumulation and evolution. Overall, the co-existence of fracture-filling hydrates and pore-filling hydrates formed from the same supply of thermogenic gas and biogenic gas was inferred through comprehensive study and comparison with adjacent hydrate drilling areas. This article is the first systematic study of the characteristics of hydrate accumulation under the fluid seepage background in the Beikang Basin, and it provides a favorable reference for revealing the relationship between deep-sourced fluid seepage and hydrate formation. However, more exploration work needs to be conducted to confirm the above assumptions.