Anastomotic Angle Research Articles

23. Optimal Anastomotic Angle for Prevention of Shear Related Thrombosis in Microsurgical End-to-Side Anastomosis

23. Optimal Anastomotic Angle for Prevention of Shear Related Thrombosis in Microsurgical End-to-Side Anastomosis

Experimental Study On Anastomotic Hemodynamics Using Tomographic Particle Image Velocimetry

Fluid mechanics is an important factor to the failure of the graft anastomosis surgery. In order to better understand the mechanism of restenosis and graft failure of the anastomosis from the perspective of fluid mechanics, an end-toside silicone anastomosis model with 45° anastomotic angle was used for research. The anastomosis model was connected to a continuous flow loop. where the flow rate can be adjusted during the experiment to simulate several conditions. The tomographic particle image velocimetry (TPIV) was applied to obtain the internal three-dimensional and three-component (3D-3C) flow field. The hemodynamics inside the anastomosis model was quantitatively analyzed based on the averaged 3D-3C flow field. The results present that there are phenomena such as recirculation, spiral flow, flow stagnation, and large vortex structures inside the anastomotic flow field. The oscillation of the recirculation zone size and flow stagnation point indicate the fluid stimulation to the endothelial cells. Also, the double spiral vortex structure could cause high local shear stress, which in turn cause trauma to the red blood cells and lead to local coagulation. Besides, thanks to the 3D-3C flow field, the wall shear stress (WSS) on the entire model wall was obtained, which enables us to predict the mechanical influence to the intimal hyperplasia. The local low WSS was found near the graft toe and recirculation regions, while the local high WSS was found on the host vessel bottom where the jet directly impinges. The abnormal flow phenomena can explain the high-risk regions in the anastomosis, where the stenosis and intimal hyperplasia are prone to appear. The 3D-3C flow field based on the in vitro experiment can strengthen the understanding of the anastomotic restenosis pathology and provide further reference for the surgery improvement.

#3215 RHE EFFECT OF ANASTOMOTIC ANGLE ON MATURATION OF AUTOGENOUS ARTERIOVENOUS FISTULA AFTER END-TO-SIDE ANASTOMOSIS OF CEPHALIC VEIN AND RADIAL ARTERY

Abstract Background and Aims Arteriovenous fistula (AVF) is the preferential choice of haemodialysis (HD) access, but failure of maturation of AVF is common. A previous French study had demonstrated reduced primary patency of radial-cephalic fistula with anastomotic angles < 30°. We have designed a study to determine if the angle of anastomosis affects the maturation of AVF in Chinese patients. Method We retrospectively studied our chronic patients who underwent the first cephalo-radial end-to-side anastomosis of AVF surgery at our Hospital from November 2019 to September 2022. All AVFs have been constructed by two of our dedicated nephrologists. The nephrologists performed the dissection and construction of the anastomosis according to the patient's anatomy. The angle of the anastomosis was not decided a priori and special care was given not to kink or twist the vein during the procedure. The AVF was defined as mature at 3 months if the blood flow was ≥ 500 ml/min and/or if the AVF was able to support adequate dialysis thrice a week. The patients were divided into two groups for evaluation using 45° of the AFV's anastomotic angles as cut-offs. The study has been approved by the local research and ethics committee. Statistics analysis: The IBM SPSS Statistics 26 software was used. The baseline characteristics of the two groups were analyzed using univariate analysis to find out if there was any statistical difference. The K-M curve was used to analyze if there was any statistical difference in AVF maturation between the two groups. Logistic regression was used to analyze the rate of maturation between the two groups, adjusted for confounding factors (including baseline characteristics and variables that have been shown as risk factors in previous studies, such as age, female gender, diabetes, preoperative vessel diameter, etc.), to determine whether the angle of anastomosis was an independent factor. Results A total of 159 Chinese patients were included in the study. The overall AVF maturation rate at 3 months was 93.08% (148/159 cases). Table 1 showed the patients’ baseline characteristics based on the AVF outcome. Table 2 showed the patients’ parameters in relation to different anastomotic angles (group 1: anastomotic angle ≤45°; group 2: >45°). The median time to AVF maturation of either group was 5 weeks (P = 0.9057, 95% CI 0.725-1.421) with no statistical difference. There was no statistical difference between the two groups in terms of age, gender, preoperative venous and arterial diameters, states of diabetes, coronary heart disease, peripheral vascular diseases, smoking, or biochemical parameters. Multivariate logistic regression analysis showed that there was no statistical difference between the two groups in AVF maturation rate at 3 months (OR = 0.976, 95% CI 0.273-3.489, P = 0.971). There was also no statistical difference after adjustment (OR = 0.863, 95% CI 0.231-3.233, P = 0.827). Conclusion This study has not established nor confirmed to any meaningful degree any relationship between the anastomotic angle using 45° as a cut-off and the maturation rate of AVF in Chinese patients at 3 months. Our overall AVF maturation rate was very high and none of the traditional risk factors for failed AVF nor the degree of anastomotic angle have any demonstrable effect on AVF maturation. The success might have been in part due to the skill and dedication of the nephrologists as operators. A prospective study involving a bigger patient group is necessary to further explore the effect of anastomotic angle on AVF maturation if any.

Effects of Anastomotic Angles and Distances of the Bypass Graft to the Stenosis on Blood Flow Hydrodynamics in a Bypass Grafting Coronary Artery

It is believed that the proper distance between the grafting location and the stenosis location and the appropriate angle of graft or transplantation in the blocked artery of the heart are two important factors in the removal or decrease of reappearance and re-development of intimal hyperplasia (IH), blood clotting, and re-blockage of the surgical artery. In the present study, a 3-D geometry of the host coronary artery as non-elastic with 75% symmetric axial cross-sectional area reduction is considered. The main assumptions were incompressible, laminar, steady-state, Newtonian, and non-Newtonian (with Herschel Bulkley model) blood flow. The 3-D Navier-Stokes equations coupled with the non-Newtonian constitutive model were solved numerically using a finite volume method with the procedure of the SIMPLE program. Shear stress distribution was obtained on the areas of potential re-obstruction and the occurrence of IH such as the Toe, Heel, arterial bed, suture location, and graft artery walls. Based on the results, the distribution of wall shear stress near the Heel, Toe location, and the intersection of the host and graft arteries suddenly increased dramatically. Wall shear stress (WSS) distribution was obtained in the areas of hyperplasticity re-incidence for some important anastomosis angles of grafted arteries, i.e. α=35°,45°,65°,75°. In addition, the increase in the angle of the graft artery caused a sharp increase in the shear stress on the area after the graft and the arterial bed in front of the branching region, and the shear stress decreases in the pre-graft region. Therefore, the excessive angle of the graft artery can cause damage to the arterial endothelial cells in the surrounding suture region.

Comparison of different anastomosis angles in radiocephalic fistula with modified functional end-to-side anastomosis

ObjectiveFunctional vein end to arterial side (ETS) anastomosis uses vein side to arterial side anastomosis with distal vein ligation, which is different from traditional ETS anastomosis. To date, there are no studies concerning different anastomotic angles of fistula with functional ETS anastomosis. The purpose of the study was to analyze the clinical outcomes concerning different anastomotic angles of functional ETS anastomosis in radiocephalic fistula.MethodsBetween January 2018 and December 2020, we performed a prospective cohort study concerning functional ETS anastomosis in radiocephalic fistula. According to vascular anatomy of patients, the anastomosis angles of fistula were designed at 30 ≤ angle ≤ 50°, 50 < angle ≤ 70°, and 135° smooth obtuse angle. The end points were the primary patency rate (PPR), the secondary patency rate (SPR) and the cumulative rate of reintervention (CRR) near anastomotic venous segment.Results124 patients with functional ETS anastomosiss were enrolled in this study. Pearson χ2 test showed that the group of 135°anastomosis angle had the maximum distance between arteries and veins, and the group of 30–50°anastomosis angle had the minimum distance between arteries and veins (P < 0.01). 30–50°anastomosis angle had the highest PPR at 12 months (P = 0.03) and the lowest CRR near anastomotic venous segment at 3 months (P = 0.04) and 12 months (P = 0.01). There were no significant differences among different anastomosis angles concerning the SPR within 12 months (P > 0.05). Kaplan–Meier and log-rank analysis showed that 30–50°anastomosis had the highest PPR (P = 0.03) and the lowest CRR near anastomotic venous segment (P = 0.01). A multivariable Cox model showed anastomotic angle was an independent factor predictive of the PPR (P = 0.04) and the CRR near anastomotic venous segment (P = 0.03). 50–70°anastomosis angle was a risk factor of decreasing PPR (P = 0.03). 50–70° (P = 0.01) and 135° (P = 0.03) anastomosis angle were both obvious risk factors of increasing CRR near anastomotic venous segment.Conclusion30–50°were the best anastomotic angles for functional ETS anastomosis, which had the highest PPR and lowest CRR near anastomotic venous segment.

Lower Extremity Reconstruction with Anterolateral Thigh Free-Flap Anastomoses: A Computational Fluid Dynamic Analysis.

The anterolateral thigh free flap is an option for repairing soft tissue defects of the distal lower extremity. This flap uses the descending branch of the lateral circumflex femoral (LCF) artery as the flap vessel. The recipient vessel in these flaps is often the anterior tibial (AT), posterior tibial (PT), or peroneal (P) arteries. Computational fluid dynamic (CFD) evaluation of anastomoses between these vessels can optimize outcomes. Thirty-eight CFD models were created to model end-to-side (ETS) and end-to-end (ETE) anastomoses for lower extremity reconstruction. Seven out of thirty-eight models represented ETS anastomoses between the LCF and AT arteries with varying anastomotic angles. Nine out of thirty-eight models represented 45-degree ETS anastomoses between varying diameters of the LCF and AT, PT, and P arteries. Nine out of thirty-eight models represented stenosis on the flap vessel and recipient vessel, pre- and post-bifurcation. Nine out of thirty-eight models represented ETE anastomoses, rather than ETS, with varying vessel diameters. Four out of thirty-eight models represented ETE anastomoses with varying regions and levels of stenosis. Stasis of blood flow in ETS models increased as anastomotic angle increased in a logarithmic relationship (R 2 = 0.918). Flow was optimized overall as flap and recipient vessel diameters approached one another. In ETS models, flap vessel and postbifurcation recipient vessel stenosis were found to substantially increase stasis. Selection of flap and recipient vessels with similar diameters can optimize outcomes in microvascular anastomoses. In the context of lower extremity reconstruction with the ALT flap, the PT artery can be recommended as a first-line recipient vessel due to its similar vessel caliber to the LCF and relative ease of surgical access compared with the P artery. Avoidance of areas of stenosis is recommended to ensure laminar flow and reduce the operative difficulty associated with performing anastomoses on nonpliable arteries. Striving for increased acuity of anastomotic angles is recommended to optimize the flow in ETS microvascular anastomoses.

Utilizing ultra-small volume graft in auxiliary liver transplantation for portal hypertension

Objective: To examine the clinical effect of auxiliary liver transplantation with ultra-small volume graft in the treatment of portal hypertension. Methods: Twelve cases of portal hypertension treated by auxiliary liver transplantation with small volume graft at Liver Transplantation Center,Beijing Friendship Hospital, Capital Medical University between December 2014 and March 2022 were studied retrospectively. There were 8 males and 4 females,aged 14 to 66 years. Model for end-stage liver disease scores were 1 to 15 points and Child scores were 6 to 11 points. The grafts was derived from living donors in 9 cases,from split cadaveric donors in 2 cases,from whole cadaveric liver of child in 1 case. The graft recipient body weight ratios of 3 cadaveric donor livers were 0.79% to 0.90%, and of 9 living donor livers were 0.31% to 0.55%.In these cases, ultra-small volume grafts were implanted. The survivals of patient and graft, complications, portal vein blood flow of residual liver and graft, abdominal drainage and biochemical indexes of liver function were observed. Results: All the grafts and patients survived. Complications included outflow tract torsion in 2 cases, acute rejection in 1 case, bile leakage in 1 case, and thyroid cancer at the later stage of follow-up in 1 case, all of which were cured. The torsion of outflow tract was attributed to the change of anastomotic angle after the growth of donor liver. After the improvement of anastomotic method, the complication did not recur in the later stage. There was no complication of portal hypertension. The measurement of ultrasonic portal vein blood flow velocity showed that the blood flow of residual liver decreased significantly in the early stage after operation, and maintained a very low blood flow velocity or occlusion in the long term after operation, and the blood flow of transplanted liver was stable. Conclusions: Auxiliary liver transplantation can implant ultra-small donor liver through compensation of residual liver. This method may promote the development of living donor left lobe donation and split liver transplantation. However, the auxiliary liver transplantation is complex, and it is difficult to control the complications. Therefore, this method is currently limited to centers that are skilled in living related liver transplantation and that have complete ability to monitor and deal with complications.

Computational Fluid Dynamic Evaluation of Deep Inferior Epigastric Artery Perforator (DIEP) Flap End-to-Side Anastomosis.

BackgroundEnd-to-side (ETS) microvascular anastomoses are utilized within deep inferior epigastric artery perforator (DIEP) flap breast reconstruction procedures. Optimization of these anastomoses via a computational fluid dynamic (CFD) model can minimize ischemia and contribute to flap success.Methods A CFD model of a deep inferior epigastric artery to internal mammary artery anastomosis was constructed with OpenFOAM software (OpenCFD Ltd., Bracknell, UK). Blood was modelled as an incompressible Newtonian fluid. Viscosity and density were assumed to be constant throughout the simulation. Mean arterial pressure was held constant at 100 mmHg. Individual virtual meshes were created for 30-, 45-, 60-, 75-, and 90-degree anastomotic angle simulations. Fluid flow was visualized with line integral convolution (LIC) and pure fluid velocity (PFV) techniques. Vessel wall shear stress (WSS) was also visualized.Results The LIC revealed blood recirculation was associated with large anastomotic angles with minimal to no recirculation seen in the 45- and 30-degree simulations. Any recirculation visualized was confined to the toe of the bifurcation. This recirculation was associated with stagnation in the toe of the graft vessel as well, as visualized by the PFV model. A linear relationship was identified between anastomotic angle and percentage of stagnant fluid, with stagnation increasing as the anastomotic angle increased. Wall shear stress increased with the anastomotic angle and was concentrated in the heel and toe of the model.Conclusions The CFD modelling shows that increased acuity of anastomotic angles in ETS DIEP flaps is essential to minimize stagnation, recirculation, and WSS. Successful implementation of this recommendation may directly decrease the risk of flap failure from ischemia.

Effect of Anastomosis Angles on Retrograde Perfusion and Hemodynamics of Hybrid Treatment for Thoracoabdominal Aortic Aneurysm

Hemodynamic effects on the retrograde visceral reconstruction (RVR) for thoracoabdominal aortic aneurysms treatment by anastomotic angle remains unclear. This study aims to qualitatively and quantitatively investigate the effects of different anastomotic angles on hemodynamics and patency. Three RVR models with 45°, 60° and 90° anastomotic angles were reconstructed respectively by manipulating apostoperative patient-specific model. The manipulated models of the RVRs were numerically simulated and analyzed in terms of hemodynamics including theinstant and cumulative patency, flow pattern and indicators based on wall shear stress (WSS). Although a smaller anastomotic angle may decrease the patency rate of common iliac arteries, it can improve the visceral perfusion during a cardiac cycle. More importantly, RVR with the smallest anastomotic angle experienced a minimal low time-averaged wall shear stress, high oscillatory shear index and relative residence time in the anastomosis region, whereas the largest anastomotic angle can introduce more unfavorable WSS in the graft trunk. Furthermore, a spiral flow pattern was observed in the proximal graft trunk of all three models, where no high-risk shear distribution was detected in this region. A smaller anastomotic angle may have more benefits of hemodynamic environment in RVR, especially the WSS distribution and flow pattern in the graft trunk. We may also suggest that additional stents or an extended cuff for the graft can be used to induce spiral flow intentionally, which can further improve local hemodynamic environment and long-term prognosis.

Endothelial nitric oxide synthase (eNOS) mediates neointimal thickness in arteriovenous fistulae with different anastomotic angles in rats.

It is known that the anastomotic angle can influence neointimal hyperplasia and patency in arteriovenous fistulae (AVF). Endothelial nitric oxide synthase (eNOS) is released from the vascular endothelium and can inhibit neointimal hyperplasia. Therefore, here, we aimed to test the hypothesis that the manipulation of eNOS expression could influence neointimal thickness in a rat AVF model with different anastomosis angles. Rat carotid artery (inflow, CA) and jugular vein (outflow, JV) AVF were created with acute, blunt, or end-to-end (ETE) anastomosis angles. Aspirin was used to increase eNOS expression in the acute angle group, while N(G)-nitro-L-arginine methyl ester (L-name) was used to decrease eNOS expression in the obtuse angle group. The rats were sacrificed on day 21, and tissues were harvested and analyzed histologically and with immunostaining. A larger anastomosis diameter (p < 0.016) and smaller neointimal area (p < 0.01) were observed in the obtuse and end-to-end (ETE) groups compared to in the acute group. In the acute angle group, there were more proliferating cell nuclear antigen (PCNA) and α-actin dual-positive cells (p < 0.0001) and fewer phospho (p)-eNOS-positive endothelial cells (p < 0.0001) in the neointima than in the obtuse and ETE angle groups. On treating the acute angle and blunt angle groups with aspirin and L-name, respectively, no significant differences in the neointima/lumen rate were observed (p = 0.6526) between the groups; however, there were fewer von Willebrand factor (vWF) and p-eNOS dual-positive cells in the obtuse angle group treated with L-name (p = 0.0045). We demonstrated that eNOS plays an important role in neointimal hyperplasia in AVF with different anastomosis angles; further, eNOS could potentially be used as a therapeutic target in patients with AVF in the future.

Optimization of Maturation of Radio-Cephalic Arteriovenous Fistula Using a Model Relating Energy Loss Rate and Vascular Geometric Parameters

The main reason for the early failure of radio-cephalic arteriovenous fistula (RCAVF) is non-maturity, which means that the blood flow rate in the fistula cannot increase to the expected value for dialysis. From a mechanical perspective, the vascular resistance at the artificially designed anastomosis causes an energy loss that affects blood flow rate growth and leads to early failure. This research studied how to maximize the RCAVF maturity and primary patency by controlling the energy loss rate. We theoretically analyzed and derived a model that evaluates the energy loss rate Eavf in RCAVF as a function of its blood vessel geometric parameters (GPs) for given flow rates. There was an aggregate of five controllable GPs in RCAVF: radial artery diameter (Dra), cephalic vein diameter (Dcv), blood vessel distance between artery and vein (h), anastomotic diameter (Da), and anastomotic angle (θ). Through this analysis, it was found that Eavf was inversely proportional to Dra, Dcv, Da, and θ, whereas proportional to h. Therefore, we recommended surgeons choose the vessels with large diameters, close distance, and increase the diameter and angle of the anastomosis to decrease the early failure of RCAVF. Simultaneously, we could explain the results of many clinical empiricisms with our formula. We found that increasing Dcv and θ was more significant in reducing Eavf than increasing Dra and Da. Based on our model, we could define two critical energy loss rates (CELa, CELb) to help surgeons evaluate the blood vessels and choose the ideal range of θ, and help them design the preoperative RCAVF plan for each patient to increase the maturity and the primary patency of RCAVF.

Implanted blood vessel external support device (VasQ™) for creation of hemodialysis arteriovenous fistula: A single-center experience.

the external support device VasQ is intended to promote arteriovenous fistula (AVF) maturation by maintaining the optimal anastomotic angle in order to minimize blood flow disturbances around the anastomotic area. The aim of the study is to assess efficacy and safety of the VasQ device both in brachiocephalic and radiocephalic fistulae. a single institution prospective study was conducted with implantation of the VasQ device during AVF creation. Clinical and Doppler ultrasounds evaluations were performed at day-1, 1, 6, and 12 months for assessment of device-related adverse events, AVF maturation and patency. Moreover, volume flow rate and diameter of outflow vein were measured. A total of 16 patients were enrolled. Ten brachiocephalic and 6 radiocephalic AVFs were created with VasQ. Preoperatively cephalic vein diameter was 3.6 ± 0.9 mm. our population included 13 male and 3 females patients, 9 end stage kidney disease in conservative therapy, 4 dialysis treated patients, and 3 transplanted patients; mean age was 74.0 ± 8.1 years; no severe device-related adverse events were observed. Primary patency at 1, 6, and 12 months was 100%, 87.5%, and 67.7%, respectively, while secondary patency was 100%, 100%, and 78.3%, respectively. Comparing brachiocephalic to radiocephalic AVFs no significant differences in patency rates were seen. Overall maturation rate was 94% (15/16). Mean vein diameter measured with Doppler ultrasound at postoperative day-1 and at 1, 6, and 12 months was 5.0 ± 1.0, 5.9 ± 0.9, 7.2 ± 1.6, and 7.9 ± 1.4 mm, respectively, with a mean flow rate at the brachial artery of 841 ± 176, 1052 ± 224, 1261 ± 490, and 1348 ± 477 ml/min, respectively. in our limited experience VasQ was safe, with high maturation and patency rates. Positive results suggest a potential benefit for VasQ in AVF.

The Anastomotic Angle of Hemodialysis Arteriovenous Fistula Is Associated With Flow Disturbance at the Venous Stenosis Location on Angiography.

The juxta-anastomotic stenosis of an arteriovenous fistula (AVF) is a significant clinical problem in hemodialysis patients with no effective treatment. Previous studies of AV anastomotic angles on hemodynamics and vascular wall injury were based on computational fluid dynamics (CFD) simulations using standardized AVF geometry, not the real-world patient images. The present study is the first CFD study to use angiographic images with patient-specific outcome information, i.e., the exact location of the AVF stenotic lesion. We conducted the CFD analysis utilizing patient-specific AVF geometric models to investigate hemodynamic parameters at different locations of an AVF, and the association between hemodynamic parameters and the anastomotic angle, particularly at the stenotic location. We analyzed 27 patients who used radio-cephalic AVF for hemodialysis and received an angiographic examination for juxta-anastomotic stenosis. The three-dimensional geometrical model of each patient’s AVF was built using the angiographic images, in which the shape and the anastomotic angle of the AVF were depicted. CFD simulations of AVF hemodynamics were conducted to obtain blood flow parameters at different locations of an AVF. We found that at the location of the stenotic lesion, the AV angle was significantly correlated with access flow disturbance (r = 0.739; p < 0.001) and flow velocity (r = 0.563; p = 0.002). Furthermore, the receiver operating characteristic (ROC) curve analysis revealed that the AV angle determines the lesion’s flow disturbance with a high area under the curve value of 0.878. The ROC analysis also identified a cut-off value of the AV angle as 46.5°, above or below which the access flow disturbance was significantly different. By applying CFD analysis to real-world patient images, the present study provides evidence that an anastomotic angle wider than 46.5° might lead to disturbed flow generation, demonstrating a reference angle to adopt during the anastomosis surgery.

The influence of the preoperative thickness of the abdominal cavity on the gastrojejunal anatomic position and delayed gastric emptying after pancreatoduodenectomy

BackgroundWe aimed to investigate the hypothesis that preoperative thickness of the abdominal cavity influenced on the gastrojejunostomy position and the incidence of delayed gastric emptying (DGE) after pancreatoduodenectomy. MethodsBetween January 2009 and December 2018, consecutive patients who underwent subtotal stomach-preserving pancreatoduodenectomy were retrospectively reviewed. Thickness of the abdominal cavity at the level of the celiac axis (TACC) and umbilicus (TACU) were measured using computed tomography before surgery. The ventral deviation of the gastrojejunostomy was evaluated as the sagittal fundus anastomotic angle (SFAA) using sagittal computed tomography images taken after surgery. ResultsA total of 281 patients were included. Of these, clinically relevant DGE (CR-DGE) was observed in 47 patients. TACC was significantly correlated with SFAA (R = 0.53, P < 0.001). Both TACC and SFAA were significantly greater in patients with CR-DGE compared to those without CR-DGE. In contrast, TACU was not associated with SFAA and the incidence of CR-DGE. Multivariate analysis revealed that TACC >110 mm (odds ratio, 3.07; p = 0.002) and pancreatic fistula (odds ratio, 2.71; p = 0.013) were identified as independent risk factors for CR-DGE. ConclusionThickness of the upper abdominal cavity had a significant influence on gastrojejunal anatomic position and the development of CR-DGE after pancreatoduodenectomy.

The effect of anastomotic angle and diameter ratio on flow field in the distal end-to-side anastomosis.

Flow fields in the distal end-to-side anastomosis of coronary artery bypass graft are associated with intimal hyperplasia and bypass failure. This work aims to demonstrate the effect of anastomotic angle and diameter ratio on flow field of coronary artery bypass graft. The flow fields inside polydimethylsiloxane models of coronary artery bypass graft with various anastomotic angles (α = 30°, 45°, 60° and 75°) and different diameter ratios (Φ = 0.78 and 1.11) are investigated using particle image velocimetry and computational fluid dynamics method under pulsatile flow condition. The results show that the anastomotic angle is positively correlated with the number and area of the recirculation zone, and the flow field disturbance at the anastomosis will develop in the same direction. Compared with that of Φ = 0.78, when Φ = 1.11, the flow fields at the anastomosis are relatively smoother with less turbulence.

A mathematical model to evaluate hemodynamic effects of the graft anastomosis in coronary surgery.

The durability and patency of a coronary graft can be negatively affected by technical factors that induce thrombosis of the graft and poor prognosis of patients undergoing coronary artery bypass grafting. Technical factors include the inclination angle of the coronary anastomosis and the alignment between the main vessel and the inserted vessel as graft. We have studied a mathematical model aimed to assess the best angulation of the anastomosis and the influence of a correct alignment in order to prevent the risk of early graft occlusion. From data obtained from the mathematical model, in our opinion an inclination of the anastomotic angle of at least 30° seems to be a right choice when performing a coronary artery bypass graft. In addition, the incision of the coronary vessel should be done perfectly on the same axis as that performed on the graft, since even a deviation of the axis of the anastomosis of only 10° can create turbulence of the flow in the anastomosis site, which is accentuated when the deviation reaches 20°.

Aortic regurgitation in patients with a left ventricular assist device: A contemporary review.

Aortic regurgitation (AR) developing while using a continuous-flow left ventricular assist device (CF-LVAD) affects 25% to 30% of patients within the first year of implantation and is increasingly being recognized as a cause of recurrence of symptomatic heart failure (HF). The underlying mechanisms are likely multifactorial, including changes in the leaflets of the aortic valve (AV), altered root biomechanics, and excessive left ventricular (LV) unloading, together promoting cusp remodeling and commissural fusion. Known risk factors for the development of AR while under support include advanced age, lower body surface area, systemic hypertension, large aortic root diameter, permanently closed AV, and duration of support. Further, variants in the anastomotic angle between the outflow graft and the ascending aorta have recently been recognized to induce structural changes in the aortic wall, contributing to the development and progression of AV disease. Nevertheless, it remains controversial as to whether AR on LVAD has an independent impact on prognosis, and no clear recommendation exists regarding its optimal diagnosis criteria and treatment. Herein we briefly review the literature and focus on the latest results regarding development of AR in patients supported with CF-LVADs. We also provide a structured echocardiographic approach for an accurate assessment of AV dysfunction in this challenging situation.

Impact of the gastrojejunal anatomical position as the mechanism of delayed gastric emptying following pancreatoduodenectomy

Objective: This study investigated the impact of gastrojejunal anatomical position on the incidence of delayed gastric emptying (DGE) following pancreatoduodenectomy. Methods: A total of 160 patients were included in the retrospective analysis. The relative anatomical position of the gastrojejunostomy was evaluated using the coronal and sagittal plane images of computed tomography on postoperative day 7; the coronal cardia anastomotic angle (CCAA) and the sagittal fundus anastomotic angle (SFAA) were measured. In the validation study, 64 consecutive patients were enrolled, and gastric emptying was evaluated using water-soluble contrast medium. The extent of gastric emptying was graded as grade I (no gastric dilatation and no stasis), grade II (gastric dilatation but no stasis), and grade III (gastric dilatation and stasis). Results: Patients with grades B (n=8) and C (n=22) DGE were included in the “DGE group” (n=30), and the others were included in the “non-DGE group” (n=130). The CCAA was not significantly different between the two groups, whereas the SFAA was significantly greater in the DGE group compared to the non-DGE group (median 50.3 vs. 64.5 degree, p<0.001). Multivariate analysis, including various risk factors of DGE, indicated that an SFAA >60 degrees was the only independent risk factor of DGE (odds ratio, 16.59). In the validation study, the median degree of SFAA increased as the gastric emptying grade increased (grade I, 44.3 degrees; grade II, 55.3 degrees; grade III, 60.7 degrees; p=0.014 by ANOVA). Conclusions: The gastrojejunal anatomical position following pancreatoduodenectomy has a significant impact on the incidence of DGE.

3D numerical model of blood flow in the coronary artery bypass graft during no pulse and pulse situations: Effects of an anastomotic angle and characteristics of fluid

Coronary heart disease (CHD) is a fatal condition caused by atherosclerosis or plaque on the arterial walls resulting in its breakage. Curing this disease effectively can be conducted through bypass graft surgery, which helps to restore the blood flow. However, some patients have required repeated surgery because of frequent failures of an implanted bypass graft. In this study, the stenosed coronary artery bypass graft including an analysis of the blood flow phenomena and wall shear stress, based on a three-dimensional computer model, was analyzed and developed to approach a realistic situation, inlet pulse and non-Newtonian behavior. The effects of the anastomotic angles (45°, 60° and 90°), blood characteristics (Newtonian and non-Newtonian) and inlet situations (with and without pulse) were taken into consideration. The results demonstrated that the anastomosis of 45° was the most appropriate for resolving the CHD problem and could act as a guide for medical treatment as well.

Impact of the gastrojejunal anatomic position as the mechanism of delayed gastric emptying after pancreatoduodenectomy

BackgroundThis study investigated the impact of gastrojejunal anatomic position on the incidence of delayed gastric emptying after pancreatoduodenectomy. MethodsA total of 160 patients were included in the retrospective analysis. The relative anatomic position of the gastrojejunostomy was evaluated using coronal and sagittal plane computed tomography images on postoperative day 7; the coronal cardia anastomotic angle and the sagittal fundus anastomotic angle were measured. In the validation study, 64 consecutive patients were enrolled, and gastric emptying was evaluated using water-soluble contrast medium. The extent of gastric emptying was graded as grade I (no gastric dilatation and no stasis), grade II (gastric dilatation but no stasis), or grade III (gastric dilatation and stasis). ResultsPatients with grades B (n = 8) and C (n = 22) delayed gastric emptying were included in the delayed gastric emptying group (n = 30), and the others were included in the nondelayed gastric emptying group (n = 130). The coronal cardia anastomotic angle was not significantly different between the 2 groups, whereas the sagittal fundus anastomotic angle was significantly greater in the delayed gastric emptying group compared to the nondelayed gastric emptying group (median 50.3 vs 64.5 degrees, P < .001). Multivariate analysis, including various risk factors of delayed gastric emptying, indicated that a sagittal fundus anastomotic angle >60 degrees was the only independent risk factor of delayed gastric emptying (odds ratio, 16.59). In the validation study, the median degree of sagittal fundus anastomotic angle increased as the gastric emptying grade increased (grade I, 44.3 degrees; grade II, 55.3 degrees; grade III, 60.7 degrees; P = .014 by analysis of variance). ConclusionThe gastrojejunal anatomic position after pancreatoduodenectomy has a significant impact on the incidence of delayed gastric emptying. (Surgery 2017;160:XXX-XXX.)