Peripheral Bypass Graft Research Articles

Tissue‐engineered vascular grafts for cardiovascular disease management: Current strategies, challenges, and future perspectives

AbstractCardiovascular diseases are the leading cause of mortality which primarily occurs due to the blood vessel obstruction or narrowing. Surgical procedures such as, coronary artery and peripheral artery bypass grafting frequently require vascular grafts for long‐term revascularization. However, using autogenous vessels, such as the internal thoracic artery and saphenous vein, especially for vessels with diameters less than 6 mm, are associated with number of concerns due to limited availability, invasive retrieval procedures, and aptness. To overcome these limitations, the development of tissue‐engineered vascular grafts (TEVGs) is in continuous thrust. This review comprehensively provides the potentiality of a range of artificial and naturally occurring biopolymers and their fabrication techniques, cell sources and seeding techniques to realize the state‐of‐the‐art TEVGs. Moreover, this review article presents a synopsis of insights obtained from a variety of in vitro and in vivo studies, including human clinical trials. It underscores the need for further exploration into key areas such as optimal cell sources, seeding techniques, mechanical properties, hemodynamics, graft integration, the impact of patient conditions, optimum burst pressure, sufficient suture strength, hydrophilicity, biodegradability, and related factors. In summary, the review offers insights into the current strategies, challenges, and future perspectives of TEVG.

A rat model for acute limb ischemia using microsized gelatin beads.

Acute limb ischemia (ALI) is a rapid decrease in lower limb blood flow due to acute occlusion of peripheral arteries or bypass grafts. This study aimed to establish an ALI model using microsized gelatin beads and to investigate the pathophysiological conditions. Male Sprague-Dawley rats were anesthetized, and a low or high dose of microsized gelatin beads was administered into the left femoral artery on days 0 and 7. A control, that is, normal saline (NS) group in which NS was administered in the left femoral artery, a femoral artery cut (FAC) group in which the left femoral artery was cut, and a sciatic nerve cut (SNC) group in which the left sciatic nerve was cut were prepared. After 21 days, the temperature changes and the muscle weights in the lower limbs were measured. To assess nerve damage, the L1-6 sympathetic ganglia were immunostained with activating transcription factor 3 (ATF3) antibody. In the Low-dose, High-dose, and FAC groups, a decrease in temperature was predominantly observed in the left limb. In the High-dose and SNC groups, the weight of the soleus muscle and extensor digitorum longus in the left limb decreased; however, no weight changes were observed in the Low-dose and FAC groups. Conversely, the weight of the gastrocnemius muscle significantly decreased in the Low-dose, High-dose, FAC, and SNC groups. In the High-dose and SNC groups, the number of ATF3-positive cells in the sympathetic ganglia significantly increased, and in the Low-dose, a small number of ATF3-positive cells were observed. However, ATF3-positive cells were rarely observed in the FAC and NS groups. We established an ALI rat model using microsized gelatin beads. The results of this study suggest that autonomic neuropathy in ALI is related to both muscle damage and peripheral neuropathy.

Peripheral Artery Bypass Graft for the Treatment of Ischemic Ulcer or Severe Pain of Hand in Connective Tissue Diseases.

Chronic ischemia of the hands and feet is a rare medical condition that requires surgical revascularization. In particular, digital ischemia resulting from connective tissue diseases (CTDs) is among the most important manifestations that negatively affect patients' quality of life. Here, we describe a bypass graft technique for treating digital ischemia. This study aimed to share the considerable benefits of surgical intervention for CTD and present a treatment algorithm. From 2009 to 2020, bypass graft surgery was performed on 10 patients with CTD to relieve their ischemic symptoms or ulceration. Preoperative angiography was performed, and blood distribution patterns were analyzed in detail. Based on the angiographic 4-level analysis, bypass graft surgeries were performed accordingly. The postoperative follow-up was 15 to 72 months. Pain in the hands that underwent the bypass graft surgery improved immediately after surgery. All ulcerations healed and the mean time recorded for ulceration healing was 45.7 days. Here, we propose an appropriate surgical treatment algorithm for managing CTD using arterial bypass graft surgery, and its positive long-term results demonstrate that it is an appropriate option for treating digital ischemia. In conclusion, strict measures with precise preoperative planning can provide satisfactory long-term results in patients with CTD.

Impact of Revascularization Technique on the Outcomes of Peripheral Graft Revision Procedures

The acute occlusion of a peripheral bypass graft leads to acute limb ischemia (ALI) and threatens the viability of the limb if left untreated. The aim of the present study was to analyze the results of surgical and hybrid revascularization techniques for patients with ALI due to peripheral graft occlusions. A retrospective analysis of 102 patients undergoing treatment for ALI due to peripheral graft occlusion between 2002 and 2021 was carried out at a tertiary vascular center. Procedures were classified as surgical when only surgical techniques were used and as hybrid when surgical procedures were combined with endovascular techniques such as balloon or stent angioplasty or thrombolysis. Endpoints were primary and secondary patency and amputation-free survival after 1 and 3years. Of all patients, 67 met the inclusion criteria, 41 were treated surgically and 26 by hybrid procedures. There were no significant differences in the 30-day patency rate, 30-day amputation rate, and 30-day mortality. The 1- and 3-year primary patency rates were 41.4% and 29.2% overall, respectively; 45% and 32.1% in the surgical group, respectively; and 33.2% and 26.6% in the hybrid group, respectively. The 1- and 3-year secondary patency rates were 54.1% and 35.8% overall, respectively; 52.5% and 34.2% in the surgical group, respectively; and 54.4% and 43.5% in the hybrid group, respectively. The 1- and 3-year amputation-free survival rates were 67.5% and 59.2%, overall, respectively; 67.3% and 67.3% in the surgical group, respectively; and 68.5% and 48.2% in the hybrid group, respectively. There were no significant differences between the surgical and the hybrid groups. The results of surgical and hybrid procedures after bypass thrombectomy for ALI to eliminate the cause of infrainguinal bypass occlusion are comparable with good midterm results in terms of amputation-free survival. New endovascular techniques and devices need to be established in comparison to the results of these proven surgical revascularization methods.

Popliteal access for endovascular procedures in femoropopliteal artery occlusive disease.

Even though it has been reported that femoropopliteal artery endovascular revascularization is often performed with antegrade femoral artery interventions, which are technically relatively challenging, having the advantage of better control, it has also been reported that recanalization failure may occur in approximately 20% of patients and some materials have been developed for this reason. To evaluate the safety of retrograde popliteal artery intervention and our procedural success rate for symptomatic femoropopliteal artery occlusive disease. A total of 95 endovascular revascularization procedures were performed for treating symptomatic occlusive peripheral artery disease in the study period. Inclusion criteria were defined as patients who underwent endovascular revascularization procedures for symptomatic femoropopliteal artery occlusive disease. Patients who underwent a percutaneous endovascular procedure for iliac artery or below-knee arterial occlusive disease in the same session and patients who had previously undergone peripheral arterial bypass grafting or endovascular treatment for existing femoropopliteal artery disease were excluded. We evaluated 45 peripheral endovascular procedures performed on 39 patients with a mean age of 62.49 ±11.38 years in our hospital for chronic femoropopliteal artery occlusive disease. Twelve (26.7%) of the endovascular treatment procedures were performed with retrograde access through the popliteal artery (Group 2). In neither group were any complications of arterial rupture, distal embolism, early thrombosis, or pseudoaneurysms observed. We are of the opinion that the retrograde popliteal artery technique is an effective and safe intervention option in endovascular revascularization, particularly in the revascularization of the long segment and complex femoropopliteal artery occlusions.

Small-diameter bacterial cellulose-based vascular grafts for coronary artery bypass grafting in a pig model.

Surgical revascularization is the gold standard in most cases of complex coronary artery disease. For coronary artery bypass grafting, autologous grafts are state-of-the-art due to their long-term patency. A non-negligible amount of patients lack suitable bypass material as a result of concomitant diseases or previous interventions. As a promising alternative, tissue-engineered vascular grafts made of biomaterials such as bacterial cellulose (BC) are gaining more and more attention. However, the production of small-diameter grafts (inner diameter < 6 mm) of application-oriented length (> 5 cm) and their in vivo long-term patency remain challenging. In this study, grafts of 20 cm in length with an inner diameter of 3 mm were generated in a custom-made bioreactor. To potentially improve graft compliance and, therefore in vivo patency, BC was combined with an embedded cobalt–chromium mesh. The grafts were designed for in vivo endothelialization and specific surgical properties and implanted as an aortocoronary bypass in a left anterior descending occluded pig model (n = 8). Coronary angiography showed complete patency postoperatively at 4 weeks. Following 4 weeks in vivo, the grafts were explanted revealing a three-layered wall structure. Grafts were colonized by smooth muscle cells and a luminal layer of endothelial cells with early formation of vasa privata indicating functional remodeling. These encouraging findings in a large animal model reveal the great potential of small-diameter BC grafts for coronary and peripheral bypass grafting.

Development and Preliminary Testing of Porcine Blood-Derived Endothelial-like Cells for Vascular Tissue Engineering Applications: Protocol Optimisation and Seeding of Decellularised Human Saphenous Veins.

Functional endothelial cells (EC) are a critical interface between blood vessels and the thrombogenic flowing blood. Disruption of this layer can lead to early thrombosis, inflammation, vessel restenosis, and, following coronary (CABG) or peripheral (PABG) artery bypass graft surgery, vein graft failure. Blood-derived ECs have shown potential for vascular tissue engineering applications. Here, we show the development and preliminary testing of a method for deriving porcine endothelial-like cells from blood obtained under clinical conditions for use in translational research. The derived cells show cobblestone morphology and expression of EC markers, similar to those seen in isolated porcine aortic ECs (PAEC), and when exposed to increasing shear stress, they remain viable and show mRNA expression of EC markers similar to PAEC. In addition, we confirm the feasibility of seeding endothelial-like cells onto a decellularised human vein scaffold with approximately 90% lumen coverage at lower passages, and show that increasing cell passage results in reduced endothelial coverage.

Medical Therapy Following Urgent/Emergent Revascularization in Peripheral Artery Disease Patients (Canadian Acute Limb Ischemia Registry [CANALISE I

BackgroundFollowing severe limb ischemia requiring urgent/emergent revascularization, peripheral arterial disease patients suffer a high risk of recurrent atherothrombosis. MethodsPatients discharged from Hamilton General Hospital (Hamilton, Ontario) between April 2016 and September 2017 following severe limb ischemia requiring urgent/emergent revascularization were identified via the Local Health Integration Network CorHealth database, with supplemental information from chart review. ResultsA total of 158 patients admitted for urgent/emergent revascularization were identified (148 alive at discharge). Among patients without a pre-existing indication for anticoagulation, 38.8% (n = 47) were discharged on single-antiplatelet therapy, 27.3% (n = 33) on dual-antiplatelet therapy, 19.8% (n = 24) on anticoagulants plus antiplatelet therapy, 6.6% (n = 8) on anticoagulants alone, and 2.6% (n = 3) on unknown therapy. Patients who received angioplasty with stenting were more likely be discharged on dual-antiplatelet therapy (hazard ratio [HR]: 7.14; 95% confidence interval [CI]: 2.87-17.76; P < 0.01); patients who received an embolectomy/thrombectomy were more likely be discharged on an anticoagulant alone (HR: 2.61; 95% CI: 1.00-6.81; P = 0.049); and patients who received peripheral bypass grafting were more likely be discharged on single-antiplatelet therapy (HR: 2.28; 95% CI: 1.11-4.69; P = 0.024). Neither statins (60.8% vs 56.3%; P = 0.23) nor renin–angiotensin–aldosterone system inhibitors (48.7% vs 50.6%; P = 0.58) were prescribed at higher rates at discharge, compared with the rate at admission. ConclusionsSubstantial heterogeneity exists in antithrombotic prescription following urgent/emergent revascularization. No intensification of non-antithrombotic vascular protective medications occurred during hospitalization. Clinical trials and health system interventions to optimize medical therapy in peripheral arterial disease patients are urgently needed.

Abstract No. 522 Safety and efficacy of Angio-Seal compared with manual compression in achieving hemostasis following direct puncture of PTFE grafts

To compare the safety and efficacy of Angio-Seal to manual compression in achieving hemostasis following direct percutaneous access of polyethylene terephthalate (PTFE) vascular bypass grafts This was an IRB-approved single institution, retrospective review of all patients undergoing endovascular evaluation and/or intervention performed on a peripheral bypass graft from June 2013 to July 2020. Cases in which the percutaneous access was not gained directly into the bypass graft, the bypass graft was not composed of PTFE, or in which closure was not obtained with either Angio-Seal or manual compression (e.g., planned primary surgical closure in collaborative hybrid cases) were excluded. Demographic data including patient age, sex, and co-morbidities, as well as procedural data including the type of procedure, type of graft accessed (femoral-femoral, axillary-femoral, femoral-popliteal or femoral-distal), method of access closure, peri-procedural anticoagulation and antibiotic use, and data regarding 30-day post-procedural complications were collected. For the purposes of this study, an ‘angiogram with intervention’ broadly includes all variety of angioplasty and stenting. A total of 373 cases involving lower extremity bypass interventions were reviewed. Of these, 119 unique cases resulted in 154 direct punctures of a PTFE bypass which met criteria for analysis. This included diagnostic angiograms (n = 18 (12%)), angiography with intervention (n = 66 (43%)) and utilization of catheter-directed thrombolysis (n = 70 (45%)). 116 accesses were closed with Angio-Seal and hemostasis was achieved with manual compression in the remaining 38. Overall, the access complication rate of direct PTFE puncture was 5.2%, with a major complication rate of 2.6%. A total of 4 (3.4%) complications were reported in PTFE accesses closed with Angio-Seal. Of these, 2 (1.7%) were considered major complications, including an abscess requiring surgical drainage and post-deployment stenosis requiring repair. A total of 4 (10.5%) complications were reported following manual compression, of which 2 (5.3%) developed pseudoaneurysms necessitating repair, which were considered major complications. Of the 8 total reported complications, 6 (75%) arose after catheter-directed thrombolysis, and the remaining 2 following an intervention. No complications were reported following diagnostic angiography alone. Angio-Seal is safe and effective in achieving hemostasis following PTFE puncture and has a lower rate of overall and major complications.

The abdominal waist circumference and 4-year outcomes following peripheral bypass grafting.

Current literature evaluating the relationship between obesity, utilizing measures other than the Body Mass Index (BMI), and postoperative outcomes following vascular surgery are sparse. This study aimed to investigate any association between abdominal waist circumference (AWC) and waist-hip ratio (WHR) in relation to postoperative morbidity and mortality following peripheral artery bypass graft (PABG) surgery. AWC and hip circumference (HC) were measured from pre-intervention magnetic resonance (MR) and computed tomography (CT) scans of patients undergoing elective and nonelective PABG. The AWC and WHR were assessed in relation to: the need for higher level care (i.e. level 2/3), the duration of higher level care, postoperative limb ischemia, postoperative hospital stay, graft patency on discharge and 30 day readmission, using logistic and linear regression analysis. Mortality was assessed using cox-regression analysis with calculation of hazard ratios at 30 days and 4 years. In total, 177 patient images performed between January 2014 to January 2017 were analyzed. There were no significant intra-observer and interobserver differences in measurements of AWC and HC. Pre-intervention AWC was predictive of the need for higher level care following non-elective PABG (adjusted OR 1.1 [95% CI: 1.0-1.1, P=0.026]). An inverse relationship between AWC and mortality at 4 years was also observed (adjusted HR=0.9, 95% CI: 0.9-1.0, P=0.028). However, pre-intervention WHR failed to predict mortality and morbidity. AWC may potentially be a suitable risk stratification tool in patients undergoing non-elective PABG. The association of AWC with long-term mortality outcomes require further investigation so that suitable cut-off values may be determined.

The Upper-Arm Basilic-Cephalic Loop: A Valueable Alternative for Below-Knee Arterial Reconstruction.

Despite advances of endovascular interventions, bypass surgery remains the gold standard for treatment of long and complex arterial occlusions in the lower limb. Autologous vein is regarded superior to other options. As the graft of first choice, the great saphenous vein (GSV) is often not available due to previous bypass, stripping or poor quality. Other options like arm veins (AV) are important alternatives. As forearm portions of AVs are often unusable, a graft created from the upper arm basilic and cephalic veins provides a valuable alternative. We analyzed consecutive patients treated at an academic tertiary referral center between 01/1998 and 07/2018 using arm veins as the main peripheral bypass graft. Study endpoints were primary patency, secondary patency, limb salvage and survival. In the observed time period 2702 bypass procedures were performed at our institution for below-knee arterial reconstructions. Vein grafts used included the ipsilateral GSV (iGSV; n = 1937/71.7%), contralateral GSV (cGSV; 192/7.1%), small saphenous vein (SSV; 133/4.9%), prosthetic conduits (61/2.3%) and different configurations of AV (379/14%). In the majority of patients receiving AV grafts a complete continuous cephalic or basilic vein (CAV) was used (n = 292/77%). If it was not possible to use major parts of these 2 veins, either spliced arm vein grafts (SAV) (42/11%) or an upper arm basilic-cephalic loop graft (45/12%) were used. Median follow-up was 27 (interquartile range: 8-50) months. After 3 years secondary patency (CAV: 85%; SAV: 62%; loop: 66%; p = 0.125) and limb salvage rates (CAV: 79%, SAV: 68%; loop: 79%; p = 0.346) were similar between the 3 bypass options. The encouraging results of alternative AV configurations highlight their value in case the basilic or cephalic veins are not useable in continuity. Especially for infragenual redo-bypass procedures, these techniques should be considered to offer patients durable revascularization options.

Alternative Venous Conduits for Below Knee Bypass in the Absence of Ipsilateral Great Saphenous Vein

Vein is regarded superior to artificial graft in peripheral arterial bypass surgery. However, this option is often limited owing to previous use or removal of the ipsilateral greater saphenous vein (iGSV). In this case, the contralateral great saphenous vein (cGSV), the small saphenous vein (SSV), or arm veins (AV) are possible alternatives. Experience with all three grafts for below knee vein bypass is reported. Consecutive patients treated at an academic tertiary referral centre between January 1998 and July 2018 using the cGSV, SSV, or AV as the main peripheral bypass graft were analysed. Study end points were primary patency, secondary patency, limb salvage, and survival. Over the observed time period, 2642 bypass operations for treatment of peripheral artery disease with below knee target arteries were performed at the authors' institution: 1937 procedures using the iGSV; 644 bypass procedures using the cGSV (n=186; 28.9%), SSV (n=101; 15.7%), or AV (n=357; 55.4%); and 61 procedures using a prosthetic graft. The median follow up period was 2.3 years (range 9 days-18.5 years). Thirty day mortality was 1.9% for the whole group and similar between the three groups. After five years, primary and secondary patency rates were comparable between the three groups. Secondary patency was 75% (95% confidence interval [CI] 66-83) in the cGSV and SSV groups, and 65% (95% CI 57-73) in the AV group (p=.47). Limb salvage and survival after five years were, respectively, 73% (95% CI 65-81) and 89% (95% CI 82-95) in the cGSV group, 79% (95% CI 69-89) and 87% (95% CI 79-95) in the SSV group, and 74% (95% CI 68-80) and 83% (77-89) in the AV group (p=.46). All three types of alternative autologous vein graft are equal regarding outcome parameters. Vascular surgeons should consider all autologous options if their preferred choice is not available.

Arm Vein versus Small Saphenous Vein for Lower Extremity Bypass in the Absence of Both Great Saphenous Veins

Bypass surgery remains the gold standard for long and complex arterial occlusions in the lower limb. The vein is regarded superior to prosthetic conduits in peripheral arterial bypass surgery. However, this option is often limited because of previous bypass, stripping, or poor quality of the ipsilateral and/or contralateral great saphenous vein (GSV). Under these circumstances, the arm vein (AV) and small saphenous vein (SSV) are the only alternative autologous vein grafts. We analyzed all consecutive patients treated at an academic tertiary referral center between January 1998 and July 2018 using either the AV or SSV as the main peripheral bypass graft. Study end points were primary patency, secondary patency, limb salvage, and survival. In total, 416 bypass procedures using exclusively AV (n=327) or SSV (n=89) were performed. There was a predominance of male gender. The majority of risk factors were evenly distributed between groups. The mean follow-up period was 2.3years (0.9 to 13.3years). Five-year primary and secondary patency rates were 39% (95% CI: 31-47%) and 67% (59-75%) for AV and 53% (41-66%) and 76% (67-86%) for SSV, respectively (P=0.2 and 0.25). The five-year limb salvage and survival rates were 71% (68-81%) and 84% (77-90%) for AV and 78% (67-88%) and 90% (82-98%) for SSV, respectively (P=0.52 and 0.11). Both AV and SSV are equally effective alternatives for peripheral bypass if no GSV is available. Although there was a trend toward better results with the SSV, there was no significant difference between the 2 options.

Revascularization limb salvage in chronic limb-threatening ischemia: does open surgery still the best option in the era of endovascular therapy?

Introduction: Chronic limb-threatening ischemia (CLTI) is considered the most severe pattern of peripheral artery disease. It is defined by the presence of chronic ischemic rest pain, ulceration or gangrene attributable to the occlusion of peripheral arterial vessels who suffered from diabetes mellitus type 2, and also associated with physical, as well as psychosocial, consequences such as amputation and depression. Successful revascularization decreases the major amputation rate in patients with CLTI. The efficacy of peripheral bypass grafts and percutaneous transluminal angioplasty in accomplishing limb salvage has been recognized.Case Description: A 42-year-old man came to the RSUZA emergency room with chief complaints claudication above the right thigh and continuous pain (rest pain) at the right lower extremity since 9 months ago. History of finger amputation 2nd, 3rd and 4th right foot since 10 months ago at local hospital, and now there are necrotic wounds on his toes. Patients suffered from type 2 diabetes mellitus and have bad habits such as smoking 3 packs a day all the time. Physical examination has a wound in the lower leg area of more than 10 cm x 8 cm. Right ankle-brachial index (ABI) 0.6 and left ABI 1.3. CT-angiography (CTA) shows infra inguinal type D TASC II classification. A revascularization procedure is performed to salvage the limb with the right femoro-popliteal bypass technique with graft R-SVG and debridement in the right lower leg area so that chronic right lower limb ischemia can be overcome. Systemic heparinization was given post operatively and complaints of pain in the right lower limb begin to disappear. Patient was discharged on the 5th day of treatment with good results.Conclusion: Open surgical bypass continues to be a primary treatment of choice, durable approach in a significant proportion of patients. Lower extremity bypass grafting is most successful with a good quality, long, single-segment autogenous vein of at least 3.5mm diameter.Â

Initial Experience with a New Quantitative Assessment Tool for Fluorescent Imaging In Peripheral Artery Disease

Introduction - Reliable perioperative/ -interventional evaluation is often limited by wounds, medial calcinosis or altered collateral supply of the foot. Especially, objective combined visual and quantitative assessment might be helpful for intra- and perioperative quality control. Aim of the study was to investigate Indocyanine green fluorescent imaging (ICG-FI) combined with a new tool for quantitative assessment to evaluate tissue perfusion of the foot before and after peripheral bypass grafting.

Unplanned early hospital readmissions in a vascular surgery population

Patients who undergo vascular surgery are burdened by high early readmission rates. We examined the frequency and cause of early readmissions after elective and emergent admission to the vascular surgery service at our institution to identify modifiable targets for quality improvement. Over a 5-year period, all patients admitted and readmitted to the vascular surgery service were identified. Medical records were then individually reviewed to identify baseline characteristics from the index admission and the most responsible diagnosis for readmission within 28 days of discharge. Of a total of 3324 patients, 421 (12.7%) were readmitted to our institution within 28 days of discharge. Forty-seven were found to have more than 1 readmission following their index admission. The readmission rate ranged from 11.8% to 14.1% over the 5-year study period, resulting in an average readmission rate of 12.7%. There were similar rates for men (12.9%) and women (12.3%). Of the readmitted cases, 236 (63.1%) were unplanned readmissions. The most common diagnoses for unplanned readmissions were worsening of peripheral arterial disease status including complications related to peripheral bypass graft (30.9%), surgical site infections (15.3%) and nonsurgical infections (14.8%). To reduce readmission rates effectively, institutions must identify highrisk patients. In our study cohort, the most frequent pathology resulting in readmission was peripheral arterial disease. The most frequent preventable reason for readmission was surgical site infection. Interventions focused on early assessment of clinical status and wounds in addition to avoidance of infectious complications could help reduce readmission rates. Preventive resources can be efficiently targeted by focusing on subgroups at risk for readmission.

An in silico study of the influence of vessel wall deformation on neointimal hyperplasia progression in peripheral bypass grafts

Neointimal hyperplasia (NIH) is a major obstacle to graft patency in the peripheral arteries. A complex interaction of biomechanical factors contribute to NIH development and progression, and although haemodynamic markers such as wall shear stress have been linked to the disease, these have so far been insufficient to fully capture its behaviour. Using a computational model linking computational fluid dynamics (CFD) simulations of blood flow with a biochemical model representing NIH growth mechanisms, we analyse the effect of compliance mismatch, due to the presence of surgical stitches and/or to the change in distensibility between artery and vein graft, on the haemodynamics in the lumen and, subsequently, on NIH progression. The model enabled to simulate NIH at proximal and distal anastomoses of three patient-specific end-to-side saphenous vein grafts under two compliance-mismatch configurations, and a rigid wall case for comparison, obtaining values of stenosis similar to those observed in the computed tomography (CT) scans. The maximum difference in time-averaged wall shear stress between the rigid and compliant models was 3.4 Pa, and differences in estimation of NIH progression were only observed in one patient. The impact of compliance on the haemodynamic-driven development of NIH was small in the patient-specific cases considered.

Development of vascular substitutes for low-flow peripheral bypass grafting – a review

The development of alow-flow vascular prosthesis is avery topical issue. The authors present apathway for the development of aprosthesis with optimal properties based on the idea of mimicking the characteristics of abiological model (saphenous vein graft) and programming these properties in the model of the prosthetic substitute. The vascular prosthesis presented consists of three layers - anon-absorbable scaffold representing vascular &#8220;media&#8221;, and two absorbable collagen layers - pseudointima and pseudoadventitia. The basic methods of physical testing are presented - the single axis stretch test and inflation-extension test, as well as other procedures that affect the final properties. These include collagen curing, antithrombotic treatment of the inner layer and the use of sterilization methods. The designed new graft was successfully implanted in an ovine model.

Composite Porous Tubular Biopolymer Matrix of Small Diameter

One of the main problems in cardiovascular surgery is the lack of functionally reliable small-diameter (no more than 4 mm) vascular grafts required for coronary artery bypass grafting and peripheral artery and vein bypass grafting. The purpose of this work is the development of a composite biopolymer porous tubular matrix (CPTB matrix) 2 and 4 mm in diameter with adjustable resorption time and physicomechanical properties close to native blood vessels of the same diameter. The specimens of CPTB matrices with a diameter of 2 and 4 mm were produced by means of electrospinning from poly(hydroxybutyrate-co-hydroxyvalerate) and gelatin solution in hexafluoroisopropanol. The matrix structure was stabilized by treatment with glutaraldehyde (HA) vapor. It was demonstrated that the best specimen in terms of structure, physicomechanical properties, and resorption rate is the matrix obtained with the ratio of poly(hydroxybutyrate-co-hydroxyvalerate) : gelatin equal to 1 : 2 v/v in the solution and additionally crosslinked in HA vapor for 48 h. The detected slight cytotoxicity of the CBPT matrices developed is easily eliminated by treatment with an aqueous solution containing a set of amino acids. Decreasing the diameter of the substrate rod from 4 to 2 mm is accompanied by small changes in the surface structure and the physicomechanical properties of the CPTB matrix.

The Small Saphenous Vein: An Underestimated Source for Autologous Distal Vein Bypass

The small saphenous vein (SSV) is a potential vein source for bypass if neither greater saphenous vein nor arm vein is available. This study reports experience using SSV as part of an all autologous vein bypass policy. This study comprised single centre retrospective data analysis of all consecutive patients treated at an academic tertiary referral centre from January 1998 to February 2017 using the SSV as the main peripheral bypass graft. Study endpoints were primary patency, secondary patency, limb salvage, and survival. One hundred and twenty operations were performed in 118 patients using SSV. Indications were peripheral arterial occlusive disease (n=91; Rutherford classification 3: n=11; 4: n=21; 5,6: n=59), acute ischaemia (n=14), popliteal artery aneurysm (n=12), and bypass revisions (n=3). Median follow up was 30.5 months (10 months-13.7 years). Primary patency after one, three and five years was 68% (CI: 59-77%), 58% (49-68%), and 54% (45-64%). Secondary patency was 83% (76-89%) after one year and 77% (69-85%) after three and five years. Limb salvage after one year was 88% (82-94%) and 78% (70-86%) after five years. Survival was 96% (92-99%) after one year and 91% (85-97%) at five years. Multivariable analysis identified redo surgery as an independent risk factor. Patients receiving a primary (n=59) vs. a redo bypass (n=61) were compared. Primary patency and secondary patency were both significantly better in the primary bypass group than in the redo group (p=.0036 and p=.0003, respectively). Limb salvage was also significantly better in primary bypass patients than in the redo group (p=.0007), whereas overall survival did not differ significantly (p=.48). The SSV is a valuable alternative vein graft in peripheral bypass surgery. It achieves excellent long-term results, particularly in patients with primary procedures but also acceptable results in patients with redo surgery.