Bypass Shunt Research Articles

Patient specific numerical hemodynamics for postoperative risk assessment: series case study of EC-IC cerebral bypass

Abstract The study is devoted to the hemodynamics during cerebral vascular bypass surgery for the treatment of cerebral aneurysms in two patients. The location, morphological characteristics and treatment approaches of the patients were similar, but different outcomes were observed as a result of the performed microsurgical procedures . Computational approach was used to analyze the hemodynamic differences of aneurysms, treated via extra-intra cranial (EC-IC) cerebral bypass shunt. The paper presents a new criterion based on the energy parameters of healthy compartment of cerebral circulation. The applied approach demonstrates a new effective method of preoperative risk modelling for medical decision-making.

Detection of Field Coil Short-Circuit Fault in Synchronous Generators Based on Magnetic Bypass Shunt Effect

Detection of Field Coil Short-Circuit Fault in Synchronous Generators Based on Magnetic Bypass Shunt Effect

Fungal carotiditis with aneurysm - a rare complication of mucormycosis: presentation and management

During the COVID-19 pandemic, cases of mucormycosis (ROCM) had increased drastically, especially in the second wave. Most of these cases involved the paranasal sinuses, orbit and occasionally brain. This case report presents a rare case of mucormycosis complicated with a mycotic aneurysm of the petrous part of the internal carotid artery (ICA). A 43-year-old man presented with left-sided facial weakness for which high resolution computed tomography scan of the Temporal bones was done. A scrutiny of the computed tomography temporal bone showed evidence of osteomyelitis extending to the petrous apex around the foramen Lacerum. Computed tomography and magnetic resonance imaging of the paranasal sinus done later confirmed the diagnosis of mucormycosis. The patient underwent endoscopic surgical debridement of the nose and sinuses, with post-operative amphotericin B. After 3 weeks, the patient presented with bouts of profuse nasal bleed. Computed tomography angiogram showed an aneurysm in the petrous segment of the ICA suggestive of mycotic carotiditis complicated from mucormycosis spread along the skull base. It was successfully managed neurosurgically by a bypass shunting procedure. Mucormycosis is a disease that typically has an aggressive and startling fatality rate. ICA aneurysm is an uncommon occurrence in mucormycosis. Subjects with ROCM should be examined for brain and vascular involvement. Computed tomography angiogram should be performed as soon as possible if the skull base is involved in the ICA area. Morbidity and mortality can often be reduced by early diagnosis and interventions by a multidisciplinary team.

Maximizing Energy Output of Photovoltaic Systems: Hybrid PSO-GWO-CS Optimization Approach

Photovoltaic (PV) systems suffer from partial shade and nonuniform irradiance conditions. Meanwhile, each PV module has a bypass shunt diode (BSD) to prevent hotspots. BSD also causes a series of a peak in the power-voltage characteristics of the PV array, trapping traditional maximum Power Point Tracking (MPPT) methods in local peaks. This study aims to address these challenges by combining cuckoo search (CS), gray wolf optimization (GWO), and particle swarm optimization (PSO) to enhance MPPT performance. The results compared the yield power by Tracking the MPP using only GWO, CS, or PSO MPPT techniques and combining them. Results show that in four cases: in case 1) Uniform Irradiation in three patterns (High, Medium, and Low), In case 2) Fixed Nonuniform Irradiation, While In case 3) Slow Dynamic Nonuniform Irradiation and case 4) ) Fast Dynamic nonuniform irradiation. The efficiency (PSO + CS) 97.86%, (PSO + GWO) 97.74%, and (GWO + CS) 98.55% were the highest performers in the case 1 results in (high, medium, and low), respectively. In Case 2, the efficiency (GWO + CS) is 98.62%, and it operates more effectively under fixed nonuniform irradiance. It has the highest efficiency in both Cases 3 and 4, even though its respective PSO + GWO efficiencies are 97.45% and 97.26%. Based on these results, a hybrid mode of merging algorithms based on weather radiation conditions is proposed.

Pulmonary bypass shunt is turned off during walking in the American alligator (Alligator mississippiensis)

In non-avian reptiles, the pulmonary bypass (right-to-left) shunt directs blood away from lungs via the left aorta (LAo). At times of elevated oxygen demand, such as exercise or digestion, animals can boost systemic oxygen delivery by either increasing pulmonary bypass shunting to augment cardiac output or reducing the shunt to maximise arterial oxygen content. Previous studies on squamates and turtles showed the shunt is reduced when oxygen demand rises. In contrast, a recent study showed increased shunting during digestion in the American alligator, but whether a similar response occurs during exercise has not been reported to date. We investigated the effects of terrestrial locomotion on blood flow and shunting pattern in female juveniles of the American alligator (n=6; body mass 700-1100g). Perivascular probes were chronically implanted on the major vessels of the outflow tract: the left aorta (LAo), the left pulmonary artery (LPA), the common carotid artery (CCA), and the right aortic arch jointly with the right subclavian artery (RAo+SCA). Shunt fraction was calculated as LAo flow relative to the right ventricular output (= LAo + 2✕LPA). Experiments were performed in a walk-in environmental chamber on animals fasted for a week and equilibrated to 30°C. Upon instrumentation and recovery from surgery, animals were exercised on a level treadmill (0.5 km/h) until exhaustion. Blood flows were recorded continuously before, during and after (10+ min) exercise. Systolic blood flow in the LAo was in the forward direction (shunt on) in alligators at rest, became retrograde (shunt off) immediately upon onset of exercise, and turned anterograde (shunt on again) during recovery. Compared with flow rate values obtained at rest (1.64±0.30 ml/kg/min), average (systolic and diastolic) flow in the LAo decreased significantly during exercise (0.65±0.46 ml/kg/min), and gradually increased with time during recovery (to 1.52±0.28 ml/kg/min in the 10 th min post-exercise). In contrast, blood flow in other instrumented vessels increased during exercise, and gradually decreased during recovery. Shunt fraction was highly variable in resting animals (0.4 – 11.5%), decreased significantly during exercise, remained depressed in the 1 st min post-exercise and increased gradually during recovery to (p<0.05, mixed model ANOVA, post-hoc Dunnett’s test with rest as control). This suggests that alligators turn the pulmonary bypass shunt off during acute bouts of terrestrial exercise. According to the Fick Principle, crocodilians favour increasing arterial oxygen content, by reducing admixture of oxygenated and deoxygenated bloodstreams, over augmenting cardiac output with shunt flow. Thus, despite profound differences in their heart morphology, crocodilian and non-crocodilian “reptiles” exhibit the same response – turning the shunt off – at times of elevated oxygen demand. Whether this is modulated by exercise-induced sympathetic stimulation remains to be tested. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Two stages of salvaging an extensively necrotic foot with chronic limb‐threatening ischemia by arterialization of great saphenous vein and free latissimus dorsi musculocutaneous flap transfer for wound coverage with the arterialized vein as the recipient vessel: A case report

Patients with chronic limb-threatening ischemia (CLTI) without other options for adequate arterial revascularization could undergo deep (or distal) venous arterialization for limb salvage. Additionally, patients with extensive foot wound with CLTI sometimes require free flap transfer for limb salvage. We herein report a case of successful reconstructive limb-salvage surgery for an extensively necrotic foot with CLTI, using a two-stage operation involving venous arterialization using foot-perforating veins and subsequent free flap transfer (with preservation of the arterialized vein). The patient was a 59-year-old man with CLTI. The patient's right foot had dry necrotic tissue after Lisfranc joint amputation. Only one straight-line to the posterior tibial artery was achieved after endovascular therapies (four times). At the first stage of surgery, an arterial-venous shunt bypass from the superficial femoral artery to the distal great saphenous vein (GSV) (near the foot-perforating vein) was created. Arterial blood supply reached the necrotic area via the foot venous circulation system. At the second stage of surgery, free latissimus dorsi musculocutaneous flap (8 × 27 cm) transfer with preservation of the arterialized vein was performed. The pedicle artery was anastomosed to the bypass graft (end-to-side). The pedicle vein was anastomosed to the proximal stump of the GSV (end-to-end). The flap and residual foot survived completely, at a one-year follow-up postoperatively. An indocyanine green bypass-through angiography revealed the angiosome through the venous arterialization bypass graft, which included the flap; entire forefoot; and partial regions of the midfoot and heel. This two-stage operation might be considered a useful option for limb-salvage and complete wound-healing in patients with severe non-healing wound with CLTI. The two methods could compensate and overcome the problems of either method: incomplete wound-healing after venous arterialization, and the absence of a recipient artery for free flap transfer.

Hybrid MPPT approach using Cuckoo Search and Grey Wolf Optimizer for PV systems under variant operating conditions

Photovoltaic (PV) systems are adversely affected by partial shading and non-uniform conditions. Meanwhile, the addition of a bypass shunt diode to each PV module prevents hotspots. It also produces numerous peaks in the PV array’s power-voltage characteristics, thereby trapping conventional maximum power point tracking (MPPT) methods in local peaks. Swarm optimization approaches can be used to address this issue. However, these strategies have an unreasonably long convergence time. The Grey Wolf Optimizer (GWO) is a fast and more dependable optimization algorithm. This renders it a good option for MPPT of PV systems operating in varying partial shading. The conventional GWO method involves a long conversion time, large steady-state oscillations, and a high failure rate. This work attempts to address these issues by combining Cuckoo Search (CS) with the GWO algorithm to improve the MPPT performance. The results of this approach are compared with those of conventional MPPT according to GWO and MPPT methods based on perturb and observe (P&O). A comparative analysis reveals that under non-uniform operating conditions, the hybrid GWO CS (GWOCS) approach presented in this article outperforms the GWO and P&O approaches.

Meso-Rex bypass shunt vs. transposition shunt for cavernous transformation of portal vein in children.

BackgroundCavernous transformation of the portal vein (CTPV) causes portal hypertension in children. Among Meso-Rex treatments, it is unclear whether the Meso-Rex bypass shunt (MRB) or the Meso-Rex transposition shunt (MRT) offers lower postoperative morbidity. Our objective was to evaluate postoperative outcomes, comparing MRB and MRT for children with CTPV.MethodsA retrospective study was conducted on children undergoing Meso-Rex for CTPV from January 2010 to December 2020. The primary outcome was shunt complications, including shunt stenosis and thrombus. The secondary outcome was re-operation.ResultsOf the 43 patients included, 21 underwent MRT and 22 underwent MRB. MRT was associated with a higher rate of shunt complications when compared to MRB (23.8 vs. 9.1%, p = 0.191). The patients exhibited a higher rate of re-operation under the MRT than under the MRB (19 vs. 4.5%, p = 0.138). The operative time in the MRT group was significantly shorter than in the MRB group. Compared to MRT, the reduction in the length and thickness of the spleen was significantly greater in the MRB group. The increases in platelets were significantly higher in the MRB group than in the MRT group. The postoperative shunt velocity of MRB was notably faster than MRT. There was no significant difference in postoperative portal pressure between the two groups (p > 0.05).ConclusionBoth MRB and MRT result in acceptable postoperative outcomes, but MRT is associated with higher post-shunt complications, which often increase the re-operation rate. This study suggests that MRB may offer advantages for children with CTPV.

Right-sided heart reperfusion ("Berlin bridge technique") for right ventricle support during left ventricular assist device (LVAD) implantation.

Right-sided heart reperfusion ("Berlin bridge technique") for right ventricle support during left ventricular assist device (LVAD) implantation.

Development of A Bypass Shunt Device for Integrated Uninterrupted Operation of Insulated Operating Rod of 10kV Distribution Line

Development of A Bypass Shunt Device for Integrated Uninterrupted Operation of Insulated Operating Rod of 10kV Distribution Line

Superior sagittal sinus-to-internal jugular vein bypass shunt with covered stent construct for intractable intracranial hypertension resulting from iatrogenic supratorcular sinus occlusion: technical note.

Acute occlusion of the posterior sagittal sinus may lead to dramatic increase in intracranial pressure (ICP), refractory to standard treatment. Hybrid vascular bypass of cranial venous outflow into the internal jugular vein (IJV) has seldom been described for this in recent neurosurgical literature. To describe creation of a novel vascular bypass shunt from the superior sagittal sinus (SSS) to internal jugular vein (IJV) utilizing a covered stent-Dacron graft construct for control of refractory ICP. We illustrate a patient with refractory ICP increases after acute sinus ligation that was performed to halt torrential bleeding from intraoperative injury. A temporary shunt was created that successfully controlled ICP. From the promising results of the temporary shunt, we utilized a prosthetic hybrid bypass graft to function as a shunt from the sagittal sinus to IJV. Yet the associated anticoagulation led to complications and a poor outcome. Rapid and sustained ICP reduction can be expected after sagittal sinus-to-jugular bypass shunt placement in acute sinus occlusion. Details of the surgical technique are described. Heparin anticoagulation, while imperative, is also associated with worrisome complications. Acute occlusion of posterior third of sagittal sinus carries a very malignant clinical course. Intractable intracranial hypertension from acute sinus occlusion may be effectively treated with a SSS-IJV bypass shunt. A covered stent construct provides an effective vascular bypass conduit. However, the anticoagulation risk can lead to fatal outcomes. The neurosurgeon must always strive for primary repair of an injured sinus.

Changes in Performance of Glaucoma Surgeries 1994 through 2017 Based on Claims and Payment Data for United States Medicare Beneficiaries

To evaluate trends in glaucoma procedures in the United States Medicare population and to evaluate which physicians are performing newer procedures. Analysis of publicly available claims and payment data. Surgeons and beneficiaries enrolled in United States Medicare between 1994 and2017. Data regarding payments to physicians by the Centers for Medicare and Medicaid Services (CMS) were downloaded for the years 2012 through 2017. Data regarding claims to CMS by physicians were requested and processed between 1994 and 2017. Procedure counts from both data sets then were normalized for changes in the Medicare population, with 1995 as the baseline. The normalized volumes of procedures over time were visualized, as were geographic distributions of surgeons and their volume of procedures. Trends in procedure counts over time, geographic distribution of surgeons, and their volume of procedures. The number of trabeculectomies continues to decline and now is similar to the number of tubes. Use of the relatively new trabecular bypass shunts has increased rapidly. Surgeons performing these procedures are less likely to be performing traditional glaucoma surgeries as well. The number of laser-based cyclodestruction procedures increased after introduction of the endoscopic technique and again with the introduction of so-called micropulse procedures. The procedure counts obtained with physician payment data consistently are lower than those from claims data given the limitations of the payment data. Glaucoma practice patterns change each time a new device or procedure is introduced. Collectively, the use of new microinvasive glaucoma surgery procedures has increased rapidly such that they now account for a significant majority of glaucoma surgeries. Given the almost complete lack of comparative data to inform surgeon choices regarding these procedures, it will be important that randomized studies are carried out to fill this gap.

Optimal Rex shunt procedures as a treatment for pediatric extrahepatic portal hypertension.

To assess the long-term results after Rex bypass (RB) shunt and Rex transposition (RT) shunt and determine the optimal approach. Between 2010 and 2019, traditional RB shunt was performed in 24 patients, and modified RT shunt was performed in 23 children with extrahepatic portal hypertension (pHTN). A retrospective study was conducted based on comparative symptoms, platelet counts, color Doppler ultrasonography and computed tomographic portography of the portal system, and gastroscopic gastroesophageal varices postoperatively. The portal venous pressure was evaluated intraoperatively. The operation in the RB group was notably more time-consuming than that in the RT group (P < 0.05). Compared to RT shunt, the reduction in gastroesophageal varix grading, the increases in platelets, and the caliber of the bypass were greater in the RB group (P < 0.05). Although not statistically significant, higher morbidity of surgical complications was found after RT shunt (17.4%) compared with RB shunt (8.3%) with patency rates of 82.6 and 91.7%, respectively. Additionally, patients exhibited a lower rate of rebleeding under the RB procedure (12.5%) than under the RT procedure (21.7%). The RT procedure is an alternative option for the treatment of pediatric extrahepatic pHTN, and RB shunt is the preferred procedure in our center.

European TiO2 prices drop to early 2017 levels

To evaluate trends in glaucoma procedures in the United States Medicare population and to evaluate which physicians are performing newer procedures.Analysis of publicly available claims and payment data.Surgeons and beneficiaries enrolled in United States Medicare between 1994 and 2017.Data regarding payments to physicians by the Centers for Medicare and Medicaid Services (CMS) were downloaded for the years 2012 through 2017. Data regarding claims to CMS by physicians were requested and processed between 1994 and 2017. Procedure counts from both data sets then were normalized for changes in the Medicare population, with 1995 as the baseline. The normalized volumes of procedures over time were visualized, as were geographic distributions of surgeons and their volume of procedures.Trends in procedure counts over time, geographic distribution of surgeons, and their volume of procedures.The number of trabeculectomies continues to decline and now is similar to the number of tubes. Use of the relatively new trabecular bypass shunts has increased rapidly. Surgeons performing these procedures are less likely to be performing traditional glaucoma surgeries as well. The number of laser-based cyclodestruction procedures increased after introduction of the endoscopic technique and again with the introduction of so-called micropulse procedures. The procedure counts obtained with physician payment data consistently are lower than those from claims data given the limitations of the payment data.Glaucoma practice patterns change each time a new device or procedure is introduced. Collectively, the use of new microinvasive glaucoma surgery procedures has increased rapidly such that they now account for a significant majority of glaucoma surgeries. Given the almost complete lack of comparative data to inform surgeon choices regarding these procedures, it will be important that randomized studies are carried out to fill this gap.

Aorto-pulmonary bypass shunt for intraoperative right ventricular support during LVAD implantation.

We describe a simple modification of the cardiopulmonary bypass (CPB) circuit that allows selective intraoperative circulatory support of the right ventricle during left ventricular assist device (LVAD) implantation. The addition of a side branch to the arterial line and an intermediate line connector allows selective venting and perfusion through a cannula inserted in the main pulmonary artery. This modification of the CPB circuit allows for selective evaluation of right ventricular function, titration of inotropic support, and early identification of patients that require right ventricular assist device (RVAD) support.

Surgical Mesoportal Bypass and Portosystemic Shunt Interventions

AbstractExtrahepatic portal vein obstruction is defined by obstruction of the extrahepatic portal vein with or without involvement of the intrahepatic veins and does not include isolated thrombosis of the splenic vein or superior mesenteric vein. The etiology may be congenital versus acquired and acute versus chronic. Historically, surgical intervention has been reserved for patients with symptoms refractory to medical or endoscopic management. Over time, however, advances in surgical technique and research have caused a shift in practice. The interventionalists' role is primarily to address clinically significant shunt dysfunction, including shunt stenosis and thrombosis. In this article, the authors discuss the classification and indications of surgical portosystemic conduits, pre-and postoperative imaging, and clinical signs, and endovascular techniques to address shunt dysfunction.

A comprehensive equivalent circuit model of all-vanadium redox flow battery for power system analysis

Electrical equivalent circuit models demonstrate excellent adaptability and simplicity in predicting the electrical dynamic response of the all-vanadium redox flow battery (VRB) system. However, only a few publications that focus on this topic are available. The paper presents a comprehensive equivalent circuit model of VRB for system level analysis. The least square method is used to identify both steady-state and dynamic characteristics of VRB. The inherent features of the flow battery such as shunt current, ion diffusion and pumping energy consumption are also considered. The proposed model consists of an open-circuit voltage source, two parasitic shunt bypass circuits, a 1st order resistor-capacitor network and a hydraulic circuit model. Validated with experimental data, the proposed model demonstrates excellent accuracy. The mean-error of terminal voltage and pump consumption are 0.09 V and 0.49 W respectively. Based on the proposed model, self-discharge and system efficiency are studied. An optimal flow rate which maximizes the system efficiency is identified. Finally, the dynamic responses of the proposed VRB model under step current profiles are presented. Variables such as SOC and stack terminal voltage can be provided.

Evolution of the in‐series circulation in tetrapods: form follows function

The ancestral in‐parallel circulation of tetrapods combines a single ventricle and two systemic aortae, which allow central vascular shunting. Loss of the shunt and evolution of the in‐series circulatory design, as exemplified by extant mammals and birds, involved independent acquisition of two anatomic features: a complete interventricular septum, and a single aorta. Extent and location of the interventricular septum is dictated by the expression gradient of Tbx transcription factors in the myocardium. Loss of an aorta, however, has yet to be addressed by developmental studies. Our experimental work on the American alligator suggests that the heart's outflow tract is remodelled by changes in blood flow distribution in response to environmental stressors. Flow capacity of the left aorta (a conduit for the pulmonary bypass shunt) was significantly reduced (−27%) in alligator hatchlings chronically exposed for three months to atmospheric hypoxia (12%O2), when compared to conspecifics reared in normoxia (21%O2) or hyperoxia (30%O2). In contrast, outflow tract capacities did not differ in juvenile alligators subject to 15 months of different exercise regimina (sedentary, running or swimming). We suggest that a global hypoxic episode, rather than increased activity, may have been the driving pressure behind loss of the shunt and origin of the in‐series circulation. Funded by NSF IOB0445680 and IOS922756 to JWH.

Surgical management of portal hypertension in children

The management of children with portal hypertension has dramatically changed during the past decade, with an improvement in outcome. This has been achieved by improved efficiency of endoscopic variceal control and the success of liver transplantation. Emergency surgical shunt procedures are rarely required, with acute bleeding episodes generally controlled endoscopically or, occasionally in adults, by interventional radiological procedures. Portosystemic shunts may be considered as a bridge to transplant in adults but are rarely used in this context in children. Nontransplant surgery or radiological interventions may still be indicated for noncirrhotic portal hypertension when the primary cause can be cured and to allow normalization of portal pressure before liver parenchyma is damaged by chronic secondary changes in some specific diseases. The meso-Rex bypass shunt is used widely but is limited to those with a favorable anatomy and can even be performed preemptively. Elective portosystemic shunt surgery is reserved for failure to respond to conservative management in the absence of alternative therapies.

The Utility of Recanalized Umbilical Vein Graft to the Hepato-pancreato-biliary Surgeon

The authors recently published their experience of recanalizing umbilical veins in deceased liver donors, with recanalized umbilical veins as vascular conduits for meso-Rex bypass procedures. They have since found recanalized umbilical veins to be an excellent, easy to harvest vascular conduit that can be used for multiple vascular procedures and repair. Here, they report their experience using this vessel for bypass and vascular reconstruction. They have recanalized umbilical veins and used them in a total of 5 Meso-Rex bypasses; 5 pancreaticoduodenectomies; 1 left hepatic trisegmentectomy with right portal vein (PV) resection and reconstruction; 1 right hepatectomy and 1 adrenalectomy, both with partial inferior vena cava (IVC) resection and reconstruction; 1 coronary-Rex bypass shunt for extrahepatic PV thrombosis; and 1 orthotopic liver transplantation with infrahepatic IVC anastomotic dehiscence patched with umbilical vein graft. Umbilical veins were dilated mechanically and used in situ for the meso-Rex bypass surgery; they were ligated in the space of Rex and then dilated ex vivo otherwise to be used as interposition grafts or a vein patch. A total of 15 hepato-pancreato-biliary procedures were done using the recanalized umbilical vein as graft; 2 patients required thrombectomy postoperatively with reexploration, venotomy, thrombectomy with fogarty catheter, and venotomy closure. The umbilical vein graft is a fine vascular conduit and can serve many purposes in hepatobiliary surgery.