Interposition vein cuff for anastomosis of prosthesis to small artery

Management of peripheral arterial disease in the context of a multidisciplinary limb program

Peripheral artery disease (PAD) continues to increase in prevalence worldwide due to risk factors such as advanced age, diabetes mellitus, and obesity. Critical limb ischemia (CLTI) is the advanced form of PAD that can result in a lack of healing and limb loss as the most devastating consequence. Patients with PAD, especially CLTI, benefit from multidisciplinary care to optimize outcomes by reducing cardiovascular morbidity and mortality and preventing lower extremity amputation. Collaboration between various specialties allows a focus on problems involved in treating the patient with PAD including prevention, screening, medical care, wound care, infection, and revascularization when needed. Although there is no clear definition or consensus on the structure of the PAD team, certain guidelines are applicable to most clinical scenarios emphasizing "provider champions" in leading a clinical program. A vascular specialist (vascular surgery, interventional radiology, interventional cardiology) and a soft tissue specialist (podiatry, plastic surgery) are the typical "champions," often involving orthopedics, general surgery, vascular medicine, diabetology/endocrinology, infectious disease, nephrology, and rehabilitation medicine. The team should also include wound nurses, nutritionists, occupational therapists, orthotists, pharmacists, physical therapists, prosthetists, and social workers. This paper presents a brief overview of the structure of the multidisciplinary team with key components and functions of such a team to optimize treatment outcomes for PAD and CLTI.

Tapered reinforced graft and vein cuff in the distal anastomosis as adjunct strategies for infrapopliteal prosthetic bypass graft in chronic limb-threatening ischemia: A case report

The great saphenous vein is the optimal conduit for infrapopliteal bypass surgery in chronic limb-threatening ischemia. A prosthetic bypass graft is an acceptable option when the autologous vein is unavailable and the anatomy is not favorable for endovascular therapy. However, the low patency rate of prosthetic grafts calls for adjunct strategies to improve the outcomes. Tapered reinforced grafts and vein cuffs are proposed measures. We herein present a case of a 78-year-old man with chronic limb-threatening ischemia and an extensive necrotic lesion on the dorsum of the left foot. He was successfully treated with a prosthetic bypass using two adjunct strategies to help improve patency: a tapered reinforced graft and a vein cuff in the distal anastomosis. After debridement and partial skin grafting, the wound healed completely in 2 months. The bypass graft was patent for 1 year.

Long-Term Results of Below-The-Knee Bypass Using a Prosthetic Graft with a Distal Arteriovenous Fistula Interposition

Surgical bypass is the gold standard treatment in patients affected by chronic limb-threatening ischemia in advanced GLASS stages, according to the Global Vascular Guidelines. For patients in whom an autologous graft is not available, a prosthesis could be used with the adjunct of a distal arteriovenous fistula interposition. The aim of this study was to examine the long-term results of below-the-knee surgical revascularization using a prosthesis with the distal adjunct mentioned above. From 2010 to 2020, we performed 159 lower limb below-the-knee surgical revascularizations using a prosthesis with the creation of an arteriovenous fistula interposition on the distal anastomosis. The GLASS stage was 3 in 100% of patients. The primary patency rates were as follows: 86.7% at 1 year, 57.2% at 3 years, and 12.6% at 5 years. The graft thrombosis rates were 17.4% at 1 year, 42.1% at 3 years, and 64.5% at 5 years. The amputation-free survival rates were 79% at 1 year, 76% at 3 years, and 64% at 5 years. PTFE prosthetic bypass for below-the-knee arteries using an arteriovenous fistula interposition is a good solution in patients without an autologous conduit. This technique offers reasonable graft patency and limb salvage rates.

A critical review of surgical strategies to minimise venous stenosis in arteriovenous grafts

It is inevitable that complications arising from surgical procedures are ascribed to surgical technique, and this applies to venous stenosis (VS) in arteriovenous grafts. However, despite a wide range of cellular studies, computer modelling, observational series and clinical trials, there remains uncertainty on whether surgical technique contributes to VS. This article reviews evidence from basic science, fluid dynamics and clinical data to try and rationalise the main surgical options to modify the occurrence of venous stenosis. There is sufficient data from diverse sources to make recommendations on clinical practice (size of target vein, shape of anastomosis, angle of approach, distance from venous needling, trauma to the target vein) whilst at the same time this emphasises the need to carefully report the practical aspects of surgical technique in future clinical trials.

Genesis of Crural Revascularization

BACKGROUND

The purpose of this study is to recognize those investigators responsible for initiating progress in limb salvage where runoff beyond the arterial blockage was limited to the crural vasculature and to also describe how crural bypass has evolved into the contemporary setting where endovascular options have become increasingly prominent.

METHODS

An extensive literature review of articles published from 1960 to 1979 was the basis for selecting and recognizing surgeons who pioneered infrageniculate revascularization. Documentation of patency and amputation rates were tabulated for these early series of distal limb bypass. Cases performed in the decade of interest, but not published until the 1980s, are also recognized and recorded separately.

RESULTS

Subsequent to the first tibial bypass performed in 1961 by McCaughan, a total of 746 crural bypasses were defined in the decades of interest, where possible, with overall 6-, 12-, and 36-month patencies of 76%, 59%, and 48%, respectively. There was an overall amputation rate of 17%. Life table analysis and other statistical methods were also adopted during this time.

CONCLUSIONS

Performance of crural bypass from 1960 to 1979 was analyzed in groups according to the distal anastomosis site. These results confirm the satisfactory early progress leading to further refinement in subsequent decades. It is essential that the current generation of vascular surgeons recognize the value of these early open procedures as a stable force for securing limb salvage in conjunction with evolving endovascular techniques.

Case of lower limb revascularisation using composite sequential bypass graft with a 'diamond' intermediate anastomosis

In patients with critical infracrural disease, autologous saphenous vein grafting offers the best reported conduit patency and limb salvage rates but is only feasible in approximately 30% of patients due to the lack of available or suitable vein. In the absence of a suitable length of available vein, various composite grafting techniques have been explored with the aim to improve graft longevity, maximise native vein use and improve overall clinical outcomes, including limb salvage rates. We report a case of a 66-year-old man with critical limb ischaemia and a history of venous disease, where a complex composite sequential bypass graft combining both native vein and synthetic graft, incorporated into a novel intermediate anastomotic technique in a 'diamond' configuration, offered promising results in limb salvage. This case highlights the key steps and advantages in this novel technique.

The Society for Vascular Surgery practice guidelines on follow-up after vascular surgery arterial procedures

Although follow-up after open surgical and endovascular procedures is generally regarded as an important part of the care provided by vascular surgeons, there are no detailed or comprehensive guidelines that specify the optimal approaches with regard to testing methods, indications for reintervention, and follow-up intervals. To provide guidance to the vascular surgeon, the Clinical Practice Council of the Society for Vascular Surgery appointed an expert panel and a methodologist to review the current clinical evidence and to develop recommendations for follow-up after vascular surgery procedures. For those procedures for which high-quality evidence was not available, recommendations were based on observational studies, committee consensus, and indirect evidence. Recognizing that there are numerous published reports on the role of duplex ultrasound for surveillance of infrainguinal vein bypass grafts, the Society commissioned a systematic review and meta-analysis on this topic. The panel classified the strength of each recommendation and the corresponding quality of evidence on the basis of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system: recommendations were graded either strong or weak, and the quality of evidence was graded high, moderate, or low. The resulting recommendations represent a wide variety of open surgical and endovascular procedures involving the extracranial carotid artery, thoracic and abdominal aorta, mesenteric and renal arteries, and lower extremity arterial revascularization. The panel also identified many areas in which there was a lack of high-quality evidence to support their recommendations. This suggests that there are opportunities for further clinical research on testing methods, threshold criteria, and the role of surveillance as well as on the modes of failure and indications for reintervention after vascular surgery procedures.

Flow patterns through vascular graft models with and without cuffs

The shape of a bypass graft plays an important role on its efficacy. Here, we investigated flow through two vascular graft designs-with and without cuff at the anastomosis. We conducted Digital Particle Image Velocimetry (DPIV) measurements to obtain the flow field information through these vascular grafts. Two pulsatile flow waveforms corresponding to cardiac cycles during the rest and the excitation states, with 10% and without retrograde flow out the proximal end of the native artery were examined. In the absence of retrograde flow, the straight end-to-side graft showed recirculation and stagnation regions that lasted throughout the full cardiac cycle with the stagnation region more pronounced in the excitation state. The contoured end-to-side graft had stagnation region that lasted only for a portion of the cardiac cycle and was less pronounced. With 10% retrograde flow, extended stagnation regions under both rest and excitation states for both bypass grafts were eliminated. Our results show that bypass graft designers need to consider both the type of flow waveform and presence of retrograde flow when sculpting an optimal bypass graft geometry.

Distal vein patch use and limb events after infragenicular prosthetic bypasses

OBJECTIVE

In the absence of suitable autologous vein, the use of prosthetic grafts for infragenicular bypasses in peripheral arterial disease has become standard practice. The purpose of this study was to investigate whether creating a vein patch at the distal anastomosis would further improve patency and freedom from major adverse limb events (MALEs). Furthermore, we sought to investigate whether the use of a distal vein patch (DVP) was associated with lower rates of acute limb ischemia (ALI) for those presenting with occluded prosthetic bypass graft.

METHODS

The cases of all patients undergoing infragenicular prosthetic bypass grafts between January 2009 and July 2016 were retrospectively reviewed. Demographics of the patients, clinical data, and outcomes (graft patency and MALEs) were collected. Patients were compared according to treatment group (DVP vs no DVP). A Cox regression analysis was used to analyze follow-up results.

RESULTS

During the study period, a total of 373 patients underwent infragenicular bypass at our institution; of those, 93 (24.9%) had prosthetic grafts (DVP, 39; no DVP, 54). Overall, 92 (98.9%) patients were male; the mean age was 63.3 ± 6.6 years and did not differ between the two groups. Patients undergoing prosthetic bypass with DVP were more likely to have chronic obstructive pulmonary disease (38.5% vs 14.8%; P = .009) and less likely to have chronic kidney disease (2.6% vs 20.4%; P = .011). Follow-up data were available for all patients for a median of 7.8 months (range, 1-89 months). After adjustment for differences in demographics and clinical data between the two groups, when outcomes were analyzed, MALEs were significantly lower in the DVP group (35.9% vs 57.4%; odds ratio [OR], 0.4; 95% confidence interval [CI], 0.2-0.9; P = .041). Similarly, reintervention rates were significantly lower in the DVP group (30.8% vs 50.0%; OR, 0.4; 95% CI, 0.2-0.9; P = .044). There was a trend toward higher primary patency in the DVP group (46.2% vs 35.2%; OR, 1.5; 95% CI, 0.7-3.5; P = .206) and lower rates of ALI after bypass occlusion (30.0% vs 42.9%; OR, 0.6; 95% CI, 0.2-1.8; P = .345). A Cox regression time-to-event analysis revealed late separation of freedom from MALEs for DVP relative to no DVP (log rank, P = .269).

CONCLUSIONS

In this evaluation of infragenicular prosthetic bypass grafts, the creation of a vein patch at the distal anastomosis was associated with lower reintervention rates and a trend toward improved primary patency and MALEs. Furthermore, for those presenting with occluded prosthetic bypass graft, the use of a DVP was associated with a trend toward lower rates of ALI.

Development of a Limb-Preservation Program

In the global scenario, as the prevalence of renal failure and diabetes increases, healing and limb preservation assume increasing clinical importance for patients and healthcare systems. Unfortunately, there continues to be variation in the care delivered to patients at risk of losing a limb based on geography, race, socioeconomic status, and insurance status. There are also a variety of therapeutic approaches to patients with limb-threatening ischemia; 25% undergo primary amputation, 25% undergo medical therapy, and only 50% undergo any attempt at revascularization. Nearly 50% of patients undergoing major amputation have not had a simple diagnostic arteriogram to assess the possibility of limb preservation. The Society of Vascular Surgery and the American Podiatric Medical Association have recognized the benefits of a multidisciplinary approach to limb preservation. Benefits to the patient include rapid assessment, improved healing, and enhanced revascularization. Advantages for the providers include the ability to efficiently manage complex patients with help from the appropriate specialties, an increase in referrals, enhanced identity of the institution, and clinical research and trials. Such a program requires the coordinated effort of physicians, nurses, allied health professionals, and administrators dedicated to the preservation of functional limbs. Beneficial components include identifiable space, a vascular laboratory, hyperbaric oxygen therapy, and protocol-driven care involving diagnostic and therapeutic modalities such as endovascular revascularization, open bypass, and soft tissue reconstruction. Prosthetic expertise is also important to maintain function in those patients for whom amputation is appropriate. But, the key to a program is cooperation and communication among the participants who have a passion for limb preservation. Video Journal Club ‘Cappuccino with Claudio Ronco' at http://www.karger.com/?doi=452746.

A 10-Year Experience with Complementary Distal Arteriovenous Fistula and Deep Vein Interposition for Infrapopliteal Prosthetic Bypasses

Since up to 20% of patients undergoing lower extremity revascularization do not have an adequate venous conduit, some authors have explored the use of prosthetic grafts with adjunctive techniques for lower extremity revascularization. However, the long-term graft patency of those procedures has not been well documented. The purpose of this study was to examine the long-term patency of polytetrafluoroethylene (PTFE) bypass with adjunctive arteriovenous fistula and venous interposition (AVF/VI) for infrapopliteal revascularization. Over a 10-year period, 246 lower extremity reconstructions were performed in 176 (71.5% men) patients with critical ischemia in whom a totally autogenous vein bypass was not feasible. Seventy-six limbs had undergone 1 or more failed ipsilateral infrainguinal bypasses. Indications for surgery were chronic critical limb-threatening ischemia (86%) (rest pain, ischemic ulcer, or gangrene) or acute ischemia (14%). Ages ranged from 46 to 91 years (mean 74 ±0.6 [SD] years). Risk factors such as diabetes, hypertension, coronary artery disease, end-stage renal disease, and use of tobacco were present in 49%, 49%, 52%, 8%, and 67% of the patients, respectively. During the follow-up, 112 cases (45%) required reinterventions. Twenty-seven patients (15%) required bypass revision twice. During the follow up, 56 limbs (23%) were amputated (above-the-knee amputation 25 (10%); below-the-knee amputation 31 (13%). To date, 150 (85%) patients of a total of 176 are deceased. The primary graft patency rates were as follows: at 1 year, 51%; at 2 years, 41%; 3 years, 35%; and 5 years, 24%. Limb salvage rates were as follows: 1 year, 79%; 2 years, 76%; 3 years 76%; and 5 years, 74%. Patient survival rates were as follows: 1 year, 69%; 2 years, 60%; 3 years, 54%; and 5 years, 40%. Amputation-free patient survival rates were as follows: 1 year, 66%; 2 years, 57%, 3 years, 51%, and 5 years, 30%. This technique appears to offer reasonable patency and limb salvage rates in patients in whom autogenous bypass grafts are not feasible.

Popliteal-to-Distal Bypass: Identifying Risk Factors Associated with Limb Loss and Graft Failure

Modern therapy, including endoluminal procedures and improved medical management, still yield less than desired results for tibial vessel occlusive disease. Despite the recent focus on these newer interventions, few modern series have evaluated the efficacy of popliteal-to-distal bypass procedures. The authors aimed to determine the efficacy of popliteal-distal bypass and to identify adverse prognostic factors for ultimate limb salvage. Eighty-seven patients (54 men; average age: 63 years) underwent 92 popliteal-distal bypasses. Duplex ultrasound was utilized to assess patency of all grafts. Data were analyzed by life-table analysis to determine patency rates at postoperative intervals. Median patient follow-up was 2.4 years. Major indications for bypass included chronic limb ischemia (86%) and disabling claudication (8%); 62% of the limbs were considered threatened, and 74% of the proximal anastomoses were above-knee. All procedures were technically successful. There were no perioperative (<30 days) deaths, and 86% of patients were alive at 5 years. Cumulative patency rates were 74% at 6 months, 70% at 2 years, and 63% at 5 years. Limb salvage rates closely paralleled patency rates. At 5 years, 62% of the affected limbs were intact; 72% of the limbs lost were associated with early (<180 days) bypass failures. Predictors of limb loss included early graft failure (84 days vs 1,288 days, p <0.0001), younger age (57 years vs 64 years, p = 0.039), history of previous ipsilateral vascular procedures (50% vs 21%, p = 0.03), heavy (>1 ppd) tobacco use (p = 0.001), and a thrombosed femoral-popliteal bypass at presentation (p = 0.002). When successful, popliteal-distal bypass is associated with excellent long-term patency and limb salvage rates. Early failures are often associated with limb loss. Heavy tobacco use, younger age, early graft failures, repeat revascularization, and presentation with a thrombosed femoral-popliteal graft are associated with limb loss.

Adjuncts to Improve Patency of Infrainguinal Prosthetic Bypass Grafts

The superiority of autologous venous conduit for infrainguinal arterial bypass has been well documented, especially when the bypass extends below the knee or to the tibial arteries. Nevertheless, when adequate autologous vein is not available, prosthetic bypasses (eg, polytetrafluoroethylene [PTFE] or Dacron) are often used in limb-salvage situations. The inferior long-term patency of these infrainguinal prosthetic bypasses has been documented by a number of studies. One such study reported a prospective multicenter randomized trial with only a 12% primary patency for infrapopliteal prosthetic bypasses after 4 years. Another study reported a similar experience with infragenicular bypasses with PTFE for limb salvage even for above-knee (27%, 5 year) and below-knee (25%, 5 year) femoral-popliteal bypasses. The reported PTFE graft patency was consistently inferior to that achieved with autologous vein for limb salvage. Dacron grafts appear to have similar patency rates to PTFE. In an attempt to improve prosthetic graft patency, a number of surgical and medical adjuncts have been developed. In this review, the authors discuss these adjuncts and their impact on infrainguinal prosthetic graft patency.

Long-Term Results of Infrapopliteal Bypass Using Polytetrafluoroethylene and Taylor Vein Patch for Critical Lower Extremity Ischemia

Although distal anastomotic vein patch and cuff techniques have been advocated to improve the patency of lower extremity bypass grafts with polytetrafluoroethylene (PTFE), use of this approach in the infrapopliteal position remains unproven. The purpose of this study is to evaluate the results of infrapopliteal bypass grafting using PTFE and Taylor vein patch for critical lower extremity ischemia. All patients undergoing infrapopliteal bypass grafting with PTFE and Taylor vein patch for ischemic rest pain or tissue loss were identified from the vascular surgery registry. This report describes results for surgical morbidity and mortality, patency, limb salvage, and survival for procedures performed from 1993 through 1998. Forty-two infrapopliteal bypass grafts with PTFE and Taylor vein patch were placed for critical lower extremity ischemia during the 6-year period. Surgical indications were rest pain in 25 (60%) patients and ischemic tissue loss in 17 (40%). Distal arterial anastomosis included 17 (40%) anterior tibial, 10 (24%) peroneal, eight (19%) posterior tibial, and seven (17%) tibioperoneal arteries. Follow-up ranged from 1 to 52 months (mean 17 months). Life-table primary patency, secondary patency, limb salvage, and survival at 3 years were 25%, 31%, 44%, and 66%, respectively. Infrapopliteal bypass with PTFE and Taylor vein patch for critical lower extremity ischemia has poor long-term results that are comparable to those reported for PTFE without Taylor vein patch.

Anastomotic Strategies to Improve Hemodialysis Access Patency—A Review

The number of patients with end-stage renal disease (ESRD) who require maintenance hemodialysis has risen sharply in the past 2 decades. It is estimated that more than 60% of all patients with ESRD who require chronic hemodialysis are accessed through an arteriovenous fistula (AVF) or graft (AVG), and the incidence is increasing at a rate of 2% to 4% per year. The long-term patency rate of an upper extremity AVF or AVG for hemodialysis access remains suboptimal owing in part to progressive stenosis at the venous anastomosis. This article reviews the causative factors of dialysis access-related anastomotic stenosis, or intimal hyperplasia. This article also reviews the clinical experience of various anastomotic strategies to ameliorate the hemodynamic environment in an effort to improve the clinical outcome of hemodialysis access. These strategies include the use of (1) vein cuff at the expanded polytetrafluoroethylene (ePTFE)-venous anastomosis of AVG, (2) cuffed ePTFE dialysis AVG, and (3) anastomotic devices that create an interrupted anastomosis with staples or clips.

Update on the role of the distal arteriovenous fistula as an adjunct for improving graft patency and limb salvage rates after crural revascularization

BACKGROUND

Critical ischemia of the lower limb continues to challenge the ingenuity of all interventionalists in achieving reliable, predictable, and durable patency. The objective of this study was to investigate the role of the distal arteriovenous fistula (dAVF) to enhance crural revascularization patency rates particularly when prosthetics are used.

METHODS

All patients who underwent crural bypass with dAVF since 1979 were included. Graft patency was assessed periodically by clinical examination and Doppler studies. Results were analyzed by life-table methodology to obtain primary and secondary patency rates and limb salvage rates.

RESULTS

A total of 502 crural bypass plus dAVF procedures were studied within 4 consecutive periods. Primary patency rates at 1 and 3 years for each of the 4 consecutive periods were (1) 36% and 10%, (2) 52% and 15%, (3) 54% and 31%, and (4) 70% and 46%. Corresponding secondary patency rates were (1) 43% and 17%, (2) 60% and 29%, (3) 60% and 44%, and (4) 72% and 50%. There was a statistically significant improvement for primary and secondary patency rates when comparing the last 2 periods with the first 2. Limb salvage rates also showed significant improvement for the same periods.

CONCLUSIONS

Creation of a dAVF should be considered as a component of crural revascularization when prosthetics are used. The altered hemodynamics associated with dAVF prevents overload and as a consequence, potential bypass closure. The contribution of dAVF for enhancing patency rates when autologous vein is used with compromised runoff requires further study.

Effect of swirling blood flow on vortex formation at post-stenosis

Various clinical observations reported that swirling blood flow is a normal physiological flow pattern in various vasculatures. The swirling flow has beneficial effects on blood circulation through the blood vessels. It enhances oxygen transfer and reduces low-density lipoprotein concentration in the blood vessel by enhancing cross-plane mixing of the blood. However, the fluid-dynamic roles of the swirling flow are not yet fully understood. In this study, inhibition of material deposition at the post-stenosis region by the swirling flow was observed. To reveal the underlying fluid-dynamic characteristics, pathline flow visualization and time-resolved particle image velocimetry measurements were conducted. Results showed that the swirling inlet flow increased the development of vortices at near wall region of the post-stenosis, which can suppress further development of stenosis by enhancing transport and mixing of the blood flow. The fluid-dynamic characteristics obtained in this study would be useful for improving hemodynamic characteristics of vascular grafts and stents in which the stenosis frequently occurred. Moreover, the time-resolved particle image velocimetry measurement technique and vortex identification method employed in this study would be useful for investigating the fluid-dynamic effects of the swirling flow on various vascular environments.

Optimal management of infrainguinal arterial occlusive disease

Peripheral arterial occlusive disease is becoming a major health problem in Western societies as the population continues to age. In addition to risk of limb loss, the complexity of the disease is magnified by its intimate association with medical comorbidity, especially cardiovascular and cerebrovascular disease. Risk factor modification and antiplatelet therapy are essential to improve long-term survival. Surgical intervention is indicated for intermittent claudication when a patient’s quality of life remains unacceptable after a trial of conservative therapy. Open reconstruction and endovascular revascularization are cornerstone for limb salvage in patients with critical limb ischemia. Recent advances in catheter-based technology have made endovascular intervention the preferred treatment approach for infrainguinal disease in many cases. Nevertheless, lower extremity bypass remains an important treatment strategy, especially for reasonable risk patients with a suitable bypass conduit. In this review, we present a summary of current knowledge about peripheral arterial disease followed by a review of current, evidence-based medical and surgical therapy for infrainguinal arterial occlusive disease.

Coronary artery bypass grafting hemodynamics and anastomosis design: a biomedical engineering review

In this paper, coronary arterial bypass grafting hemodynamics and anastomosis designs are reviewed. The paper specifically addresses the biomechanical factors for enhancement of the patency of coronary artery bypass grafts (CABGs). Stenosis of distal anastomosis, caused by thrombosis and intimal hyperplasia (IH), is the major cause of failure of CABGs. Strong correlations have been established between the hemodynamics and vessel wall biomechanical factors and the initiation and development of IH and thrombus formation. Accordingly, several investigations have been conducted and numerous anastomotic geometries and devices have been designed to better regulate the blood flow fields and distribution of hemodynamic parameters and biomechanical factors at the distal anastomosis, in order to enhance the patency of CABGs. Enhancement of longevity and patency rate of CABGs can eliminate the need for re-operation and can significantly lower morbidity, and thereby reduces medical costs for patients suffering from coronary stenosis. This invited review focuses on various endeavors made thus far to design a patency-enhancing optimized anastomotic configuration for the distal junction of CABGs.

Distal anastomotic vein adjunct usage in infrainguinal prosthetic bypasses

OBJECTIVE

Single-segment saphenous vein remains the optimal conduit for infrainguinal revascularization. In its absence, prosthetic conduit may be used. Existing data regarding the significance of anastomotic distal vein adjunct (DVA) usage with prosthetic grafts are based on small series.

METHODS

This is a retrospective cohort analysis derived from the regional Vascular Study Group of New England as well as the Brigham and Women's hospital database. A total of 1018 infrainguinal prosthetic bypass grafts were captured in the dataset from 73 surgeons at 15 participating institutions. Propensity scoring and 3:1 matching was performed to create similar exposure groups for analysis. Outcome measures of interest included: primary patency, freedom from major adverse limb events (MALEs), and amputation free survival at 1 year as a function of vein patch utilization. Time to event data were compared with the log-rank test; multivariable Cox proportional hazard models were used to evaluate the adjusted association between vein cuff usage and the primary end points. DVA was defined as a vein patch, cuff, or boot in any configuration.

RESULTS

Of the 1018 bypass operations, 94 (9.2%) had a DVA whereas 924 (90.8%) did not (no DVA). After propensity score matching, 88 DVAs (25%) and 264 no DVAs (75%) were analyzed. On univariate analysis of the matched cohort, the DVA and no DVA groups were similar in terms of mean age (70.0 vs 69.0; P = .55), male sex (58.0% vs 58.3%; P > .99), and preoperative characteristics such as living at home (93.2% vs 94.3%; P = .79) and independent ambulatory status (72.7% vs 75.7%; P = .64). The DVA and no DVA groups had similar rates of major comorbidities such as hypertension chronic obstructive pulmonary disease, diabetes mellitus, coronary artery disease, and dialysis dependence (P > .05 for all). Likewise, they had similar rates of distal origin grafts (13.6% vs 12.5%; P = .85), critical limb ischemia indications (P = .53), and prior arterial bypass (58% vs 47%; P = .08). The DVA group had a higher rate of completion angiogram performed (55.7% vs 37.5%; P =.002) and were more likely to be discharged on coumadin (53.4% vs 37.1%; P =.01). By multivariable analysis, use of a distal DVA was protective against MALEs (hazard ratio, 0.36; 95% confidence interval, 0.14-0.90; P = .03).

CONCLUSIONS

This contemporary multi-institutional propensity-matched study demonstrates that patients that receive distal anastomotic vein adjuncts as part of infrainguinal prosthetic bypass operations in general have more extreme comorbidities and more technically challenging operations based on level of target vessel and prior bypass attempts. After propensity-matched analysis, the use of a DVA may protect against MALEs in prosthetic bypass surgery and should be considered when feasible.

Numerical Simulation of Physiological Blood Flow in 2-way Coronary Artery Bypass Grafts

The Coronary Artery Bypass Graft (CABG) yields excellent results and remains the modern standard of care for treatment of occlusive disease in the cardiovascular system. However, the development of anastomotic Intimal Hyperplasia (IH) and restenosis can compromise the medium-and-long term effects of the CABG. This problem can be correlated with the geometric configuration and hemodynamics of the bypass graft. A novel geometric configuration was proposed for the CABG with two symmetrically implanted grafts for the purpose of improving the hemodynamics. Physiological blood flows in two models of bypass grafts were simulated using numerical methods. One model was for the conventional bypass configuration with a single graft (1-way model); the other model was for the proposed bypass configuration with two grafts (2-way model). The temporal and spatial distributions of hemodynamics, such as flow patterns and Wall Shear Stress (WSS) in the vicinity of the distal anastomoses, were analyzed and compared. Calculation results showed that the 2-way model possessed favorable hemodynamics with uniform longitudinal flow patterns and WSS distributions, which could decrease the probability of restenosis and improve the effect of the surgical treatment. Concerning the limitations of the 2-way bypass grafts, it is necessary to perform animal experiments to verify the viability of this novel idea for the CABG.

Computational estimation of fluid mechanical benefits from a fluid deflector at the distal end of artificial vascular grafts

Intimal hyperplasia at the distal anastomosis is considered to be an important determinant for arterial and arteriovenous graft failure. The connection between unhealthy hemodynamics and intimal hyperplasia motivates the use of computational fluid dynamics modeling to search for improved graft design. However, studies on the fluid mechanical impact on intimal hyperplasia at the suture line intrusion have previously been scanty. In the present work, we focus on intimal hyperplasia at the suture line and illustrate potential benefits from the introduction of a fluid deflector to shield the suture line from unhealthily high wall shear stress.

Surgical bypass: when is it best and do angiosomes play a role?

The etiology of foot lesions in diabetics is multifactorial. Arterial insufficiency, neuropathy, and susceptibility to infection are major factors contributing to the formation of nonhealing diabetic foot lesions. These factors lead to a 15% ulceration rate in diabetics with 20% resulting in amputation. This amputation rate, 4.1 per 1,000 per year, represents a risk 40 times greater for diabetics, with a subsequent second amputation in 60% by 5 years. Conversely, more than half of all lower-extremity amputations are performed in diabetic patients. Therefore, the primary goal in diabetic lower-extremity care is to heal foot ulcerations and prevent amputations and major disabilities. Lower-extremity revascularization is a major facet of achieving the goal of healing and amputation prevention. Due to the severity, distribution, and complexity of diabetic vascular disease, surgical bypass continues to play a role in attaining this goal. Surgical bypass might be the best option for diabetic patients with significant tissue loss or to revascularize the appropriate angiosome of the foot and maximize healing potential. In order to offer surgical bypass to these patients, innovative techniques might need to be considered, including venous patches and cuffs, heparin-bonded grafts, and adjunctive distal arteriovenous fistulas.

Interposition vein cuff for infragenicular prosthetic bypass graft

BACKGROUND

The use of prosthetic grafts such as polytetrafluorethylene (PTFE) or Dacron to bypass occluded arteries in the lower leg is an accepted practice in the absence of suitable autologous vein. The aim is limb salvage or functional improvement in critical limb ischaemia, but patency rates for below knee prosthetic bypasses are low. Creating a vein cuff at the distal anastomosis is thought to improve outcomes. Other techniques including the use of pre-cuffed synthetic grafts, spliced segments of vein and the creation of an arterio-venous fistula (AVF) are also used to improve patency.

OBJECTIVES

To compare the beneficial effects of using vein cuffed prosthetic grafts for below knee bypass in critical limb ischaemia with other types of reconstruction.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched May 2012) and CENTRAL (2012, Issue 5) for publications comparing prosthetic infragenicular bypass using vein cuffs with other bypass techniques.

SELECTION CRITERIA

Randomised controlled trials comparing interposition vein cuff prosthetic graft with autologous vein graft and non-cuffed prosthetic graft for infragenicular bypass in patients with critical limb ischaemia were included. Trials comparing vein cuff prosthetic grafts with or without AVF and vein cuff prosthetic grafts with pre-cuffed prosthetic grafts were also included.

DATA COLLECTION AND ANALYSIS

The trials were selected and assessed independently by two review authors.

MAIN RESULTS

Six trials with a combined total of 885 patients were included in this review. Only studies using prosthetic PTFE grafts were identified.Two trials compared PTFE graft with or without a vein cuff. In one underpowered trial for below knee bypass the cumulative primary patency rate was statistically significantly higher in the vein cuff group (80.3% versus 65.3% at 12 months and 51.8% versus 29.1% at 24 months, P = 0.03). There was no statistically significant difference in secondary patency (82.9% versus 72.5% and 58.6% versus 34.9%, P = 0.14) and limb salvage rates (86.3% versus 71.8% and 82.6% versus 62.2%, P = 0.08) at 12 and 24 months respectively. The other trial showed no statistically significant difference between the groups at three years in the below knee femoro-popliteal bypasses (primary patency rate 26% (95% confidence interval (CI) 18 to 38) and 43% (95% CI 33 to 58), secondary patency rate 32% (95% CI 23 to 44) and 42% (95% CI 31 to 56) and limb salvage rate 64% (95% CI 54 to 75) and 61% (95% CI 50 to 74) in the collar and no collar groups respectively). In the femoro-distal bypass group, the differences in primary patency, secondary patency and limb salvage rates were also not statistically significant at three years (primary patency rate 20% (95% CI 11 to 38) and 17% (95% CI 9 to 33), secondary patency rate 22% (95% CI 12 to 39) and 20% (95% CI 11 to 35) and limb salvage rate 59% (95% CI 46 to 76) and 44% (95% CI 32 to 61) in the collar and no collar groups respectively).One trial compared pre-cuffed PTFE grafts with vein cuffed grafts. There was no statistically significant difference in primary patency rate (62% pre-cuffed PTFE versus 52% vein cuff PTFE and 49% versus 44%, P = 0.53), secondary patency rate (66% pre-cuffed PTFE versus 53% vein cuff PTFE and 55% versus 50%, P = 0.30) or limb salvage rate (75% pre-cuffed PTFE versus 72% vein cuff PTFE and 62% versus 65%, P = 0.88) at 12 and 24 months respectively.One trial compared spliced vein grafts with vein cuffed PTFE grafts. At 24 months, the secondary patency rate was statistically significantly higher in the spliced vein group (86% in the spliced vein and 52% in the vein cuff group, P < 0.05). There was no statistical significant difference in primary patency rate (44% versus 50%, P > 0.05) and limb salvage rate (94% versus 85%, P > 0.05).Two trials compared vein cuff PTFE grafts with and without AVF. There was no statistical significant difference at 24 months in primary patency rate (29% versus 36%, P = 0.77; 32% versus 28%, P = 0.2), secondary patency rate (40% versus 40%, P = 0.89; 28% versus 24%, P = 0.2) and limb salvage rate (65% versus 70%, P = 0.97; 62% versus 71%, P = 0.3).

AUTHORS' CONCLUSIONS

There is evidence that a vein cuff at the distal anastomosis site improves primary graft patency rates for below knee PTFE graft, but this does not reduce the risk of limb loss. Pre-cuffed PTFE grafts have comparable patency and limb salvage rates to vein cuff PTFE grafts. The use of spliced veins improved secondary patency but this did not translate into improved limb salvage. The use of an AVF alone showed no added benefits. Evidence for a beneficial effect of vein cuffed PTFE grafts is weak and based on underpowered trials. A large study with a specific focus on below knee vein cuff prosthetic grafts, including PTFE, is required.

Systematic review and meta-analysis of vein cuffs for below-knee synthetic bypass

BACKGROUND

The aim was to investigate the possible benefit of vein cuffs for femoral to below-knee popliteal and femorodistal vessel synthetic bypass grafts.

METHODS

PubMed, the Cochrane library, Embase and ClinicalTrials.gov were searched for all studies on any clinical effect of vein cuffs on synthetic grafts. Outcomes were selected based on inclusion in two or more studies: primary patency and limb survival. The data were subjected to meta-analysis by outcome.

RESULTS

Three cohort and two randomized studies were selected for inclusion, involving 885 patients. Meta-analysis of five studies examining below-knee popliteal bypass showed a significant improvement for primary patency in cuffed grafts at 2 years, but not at 1 or 3 years (odds ratio at 2 years 0·46, 95 per cent confidence interval 0·22 to 0·97; P = 0·04). Limb salvage was significantly improved in cuffed grafts up to 2 years. Limb survival was also improved for cuffed distal grafts at 2 years (odds ratio 0·29, 0·11 to 0·75; P = 0·01) but showed no difference at any other time interval. Study quality was generally poor, with conflicting results.

CONCLUSION

There was a small but significant benefit for vein cuffs on synthetic grafts used for femoral to below-knee popliteal anastomoses, but little benefit for femorodistal anastomoses.

Effects of disturbed flow on vascular endothelium: pathophysiological basis and clinical perspectives

Vascular endothelial cells (ECs) are exposed to hemodynamic forces, which modulate EC functions and vascular biology/pathobiology in health and disease. The flow patterns and hemodynamic forces are not uniform in the vascular system. In straight parts of the arterial tree, blood flow is generally laminar and wall shear stress is high and directed; in branches and curvatures, blood flow is disturbed with nonuniform and irregular distribution of low wall shear stress. Sustained laminar flow with high shear stress upregulates expressions of EC genes and proteins that are protective against atherosclerosis, whereas disturbed flow with associated reciprocating, low shear stress generally upregulates the EC genes and proteins that promote atherogenesis. These findings have led to the concept that the disturbed flow pattern in branch points and curvatures causes the preferential localization of atherosclerotic lesions. Disturbed flow also results in postsurgical neointimal hyperplasia and contributes to pathophysiology of clinical conditions such as in-stent restenosis, vein bypass graft failure, and transplant vasculopathy, as well as aortic valve calcification. In the venous system, disturbed flow resulting from reflux, outflow obstruction, and/or stasis leads to venous inflammation and thrombosis, and hence the development of chronic venous diseases. Understanding of the effects of disturbed flow on ECs can provide mechanistic insights into the role of complex flow patterns in pathogenesis of vascular diseases and can help to elucidate the phenotypic and functional differences between quiescent (nonatherogenic/nonthrombogenic) and activated (atherogenic/thrombogenic) ECs. This review summarizes the current knowledge on the role of disturbed flow in EC physiology and pathophysiology, as well as its clinical implications. Such information can contribute to our understanding of the etiology of lesion development in vascular niches with disturbed flow and help to generate new approaches for therapeutic interventions.

A reappraisal of saphenous vein grafting

Autologous saphenous vein grafting has been broadly used as a bypass conduit, interposition graft, and patch graft in a variety of operations in cardiac, thoracic, neurovascular, general vascular, vascular access, and urology surgeries, since they are superior to prosthetic veins. Modified saphenous vein grafts (SVG), including spiral and cylindrical grafts, and vein cuffs or patches, are employed in vascular revascularization to satisfy the large size of the receipt vessels or to obtain a better patency. A loop SVG helps flap survival in a muscle flap transfer in plastic and reconstructive surgery. For dialysis or transfusion purposes, a straight or loop arteriovenous fistula created in the forearm or the thigh with an SVG has acceptable patency. The saphenous vein has even been used as a stent cover to minimize the potential complications of standard angioplasty technique. However, the use of saphenous vein grafting is now largely diminished in treating cerebrovascular disorders, superior vena cava syndrome, and visceral revascularization due to the introduction of angioplasty and stenting techniques. The SVG remains the preferable biomaterial in coronary artery bypass, coronary osteoplasty, free flap transfer, and surgical treatment of Peyronie disease. Implications associated with saphenous vein grafting in vascular access surgery for the purpose of dialysis and chemotherapy are considerable. Vascular cuffs and patches have been developed as an important and effective means of enhancing the patency rates of the grafts by linking the synthetic material to the receipt vessel. In addition, saphenous veins can be a cell source for tissue engineering. We review the versatile roles that saphenous vein grafting has played as well as its current status in therapy.

Early Results for Below-Knee Bypasses Using Distaflo

In patients who require lower extremity revascularization, prosthetic graft is a reasonable alternative in the absence of a suitable autologous vein conduit. However, prosthetic bypass grafts have limited patency, especially for infrageniculate reconstruction. Polytetrafluoroethylene grafts were geometrically modified at the distal end to increase their patency. The authors reviewed their experience with the Distaflo graft in patients who required lower extremity below-knee popliteal and tibial bypasses when no suitable autologous vein conduit was available. Chart review was conducted of the 57 patients who underwent 60 lower extremity bypasses over a 3-year period between June 2003 and April 2006. Twenty-four revascularizations were constructed to the tibial outflow sites, whereas the remaining grafts were placed to the below-knee (28) and above-knee (8) popliteal artery, respectively. Study endpoints were primary, assisted primary, secondary patency, and limb salvage at the time of follow-up. Distaflo bypass was performed at the infrageniculate level in 86.7% of cases (28 below-knee popliteal, 24 tibial). Mean follow-up time was 12 months (range, 0.5-37.5 months). At 1 year, primary, assisted primary, and secondary patencies and limb salvage rates for below-knee popliteal bypasses were 83.5%, 89.5%, 94.7%, and 94.4%, respectively. Primary, assisted primary, and secondary patencies and limb salvage rates for tibial bypasses were 44.4%, 44.4%, 63.2%, and 74.9%, respectively. Distaflo precuffed graft is a good alternative conduit for below-knee popliteal and tibial lower extremity reconstructions in the absence of an autologous vein and appears to have promising early patency and limb salvage rates even when used for tibial bypasses.

Comparison of Carbon-impregnated and Standard ePTFE Prostheses in Extra-anatomical Anterior Tibial Artery Bypass: A Prospective Randomized Multicenter Study

OBJECTIVES

The aim of this study was to find out whether carbon impregnated ePTFE vascular grafts have better long-term patency or limb salvage rates than Standard ePTFE vascular grafts in crural revascularization in patients with chronic critical ischemia.

DESIGN

Prospective randomized multicenter trial. Study endpoints were 36 months follow-up, major amputation or death.

MATERIALS

We used 6mm carbon ePTFE (Carboflo) and 6mm standard ePTFE vascular grafts (both C.R. BARD Inc./IMPRA).

METHODS

From June 1995 to November 1998, 283 patients were randomly assigned either to carbon (C) (n=140) or to standard (St) ePTFE (n=143) vascular grafts at 19 centres. A standard protocol was used with lateral extra-anatomic course of the graft to the anterior tibial artery and of a distal vein patch or cuff. More than 90% of the patients had rest pain or gangrene.

RESULTS

Two hundred and sixty-five (C=130; St=135) patients could be analysed in the intention-to-treat (ITT) group. Primary patency, secondary patency and limb salvage rates after 36 months were 33, 43 and 67% in the carbon- and 30, 38 and 58% in the standard PTFE group, respectively, (log-rank test: p=0.20, 0.12 and 0.16). Additional analyses were made per protocol (PP) and as-treated (AT). The retrospective power of the study was calculated as 79 and 83%.

CONCLUSION

The ITT, PP and AT analysis, showed no statistically significant advantage of the carbon ePTFE vascular graft in terms of patency or limb salvage over the standard ePTFE vascular graft at 36 months.