Resurrection of Chronically Occluded Prosthetic Bypass Grafts in a Single Stage with Suction Thrombectomy and Intervention.

BACKGROUND: Peripheral arterial occlusive disease (PAOD) continues to be a vexing problem despite the advent of endovascular techniques augmenting traditional open repair. At our institution, we have found there is a growing number of patients with PAOD who are vein-challenged and have undergone prosthetic bypass previously for infrainguinal arterial reconstruction. When occluded, these grafts have been abandoned for a new bypass strategy or amputation. We present a novel technique of reestablishing flow through chronically occluded prosthetic bypass grafts. METHODS: A retrospective review of a prospectively maintained database compiled at 2 institutions between 2016 and 2019 was performed. Six patients had previous prosthetic bypass grafts with 4 patients having femoral to popliteal grafts, 1 patient with a femoral to femoral graft, and 1 with a femoral to posterior tibial bypass graft. All patients had an attempted single-stage intervention to clear chronically occluded grafts. RESULTS: A total of 6 patients were included in the study. Indications for intervention were chronic, critical limb ischemia with tissue loss (3), severe claudication (2), and acute on chronic limb ischemia (1). Average time from bypass to suction thrombectomy was 29 months (6-60 months). Mean patency duration is 13 months (1-28 months). Adjunctive procedures include overnight lysis to improve outflow in 1 patient (16.6%), drug-coated balloon angioplasty (83.3%), or stents (83.3%). There were no embolic complications during these procedures. All (2) wounds healed and all are maintained on full-dose anticoagulation and/or antiplatelet therapy. CONCLUSIONS: Often, the timing of bypass graft occlusion is unknown, and the risk of embolism with lysis for chronically occluded bypass grafts is concerning with traditional peripheral intervention techniques. We report a new and unique minimally invasive approach to resurrect chronically occluded prosthetic bypass grafts often successful in just one stage. This tool offers an alternative technique for limb salvage in complex patients and as use increases, requires further interrogation.

Estimation of brachial artery volume flow by duplex ultrasound imaging predicts dialysis access maturation.

OBJECTIVE: This study validated duplex ultrasound measurement of brachial artery volume flow (VF) as predictor of dialysis access flow maturation and successful hemodialysis. METHODS: Duplex ultrasound was used to image upper extremity dialysis access anatomy and estimate access VF within 1 to 2 weeks of the procedure. Correlation of brachial artery VF with dialysis access conduit VF was performed using a standardized duplex testing protocol in 75 patients. The hemodynamic data were used to develop brachial artery flow velocity criteria (peak systolic velocity and end-diastolic velocity) predictive of three VF categories: low (<600 mL/min), acceptable (600-800 mL/min), or high (>800 mL/min). Brachial artery VF was then measured in 148 patients after a primary (n = 86) or revised (n = 62) upper extremity dialysis access procedure, and the VF category correlated with access maturation or need for revision before hemodialysis usage. Access maturation was conferred when brachial artery VF was >600 mL/min and conduit imaging indicated successful cannulation based on anatomic criteria of conduit diameter >5 mm and skin depth <6 mm. RESULTS: Measurements of VF from the brachial artery and access conduit demonstrated a high degree of correlation (R(2) = 0.805) for autogenous vein (n = 45; R(2) = 0.87) and bridge graft (n = 30; R(2) = 0.78) dialysis accesses. Access VF of >800 mL/min was predicted when the brachial artery lumen diameter was >4.5 mm, peak systolic velocity was >150 cm/s, and the diastolic-to-systolic velocity ratio was >0.4. Brachial artery velocity spectra indicating VF <800 mL/min was associated (P < .0001) with failure of access maturation. Revision was required in 15 of 21 (71%) accesses with a VF of <600 mL/min, 4 of 40 accesses (10%) with aVF of 600 to 800 mL/min, and 2 of 87 accesses (2.3%) with an initial VF of >800 mL/min. Duplex testing to estimate brachial artery VF and assess the conduit for ease of cannulation can be performed in 5 minutes during the initial postoperative vascular clinic evaluation. CONCLUSIONS: Estimation of brachial artery VF using the duplex ultrasound, termed the "Fast, 5-min Dialysis Duplex Scan," facilitates patient evaluation after new or revised upper extremity dialysis access procedures. Brachial artery VF correlates with access VF measurements and has the advantage of being easier to perform and applicable for forearm and also arm dialysis access. When brachial artery velocity spectra criteria confirm a VF >800 mL/min, flow maturation and successful hemodialysis are predicted if anatomic criteria for conduit cannulation are also present.

The comparative effectiveness of surgeons over interventionalists in endovascular repairs of abdominal aortic aneurysm.

OBJECTIVE: Comparative effectiveness research has mostly been focused on comparison of treatment techniques. The goal of the present study was to extend the research to physician specialty. BACKGROUND: Both surgeons and interventionalists (cardiologists and radiologists) are involved in endovascular repairs (EVAR) of aortic aneurysms, with different residency education, operative experience, preoperative assessment and patient selection, and postoperative continuity of care. METHODS: Retrospective analysis was performed using the Nationwide Inpatient Sample from 1998 to 2009. Patients undergoing EVAR for abdominal aortic aneurysm were identified with International Classification of Diseases, Ninth Revision, procedure code 39.71. Using physician identifiers available in the database, surgeons were identified by case experience in the same calendar year with elective open AAA repairs, arteriovenous fistula repairs, or carotid endarderectomy. Multivariate analysis adjusted for physician volume, AAA ruptured status, patient demographic and comorbidities, and hospital characteristics. RESULTS: A total of 28,094 EVARs were analyzed. Unadjusted mortality rates, length of stay, and total hospital charges were significantly higher for patients treated by interventionalists than those by surgeons (all Ps < 0.001). This difference persisted on multivariate analysis, where interventionalists were associated with increased likelihood of mortality (odds ratio = 1.39; 95% confidence interval, 1.04-1.89), longer length of stay (1.32 days; 95% confidence interval, 1.03-1.62), and higher total hospital charges ($19,312; 95% confidence interval, 16,471-22,153). CONCLUSIONS: Physician specialty is associated with patient outcomes. Surgeons are associated with improved outcomes, with lower mortality, shorter length of stay, and lower charges for EVAR cases, when compared with interventionalists. This finding has significant implications for future comparative effectiveness research and potential policy changes in patient referrals or physician admitting privileges.

The role of amputation as an outcome measure in cellular therapy for critical limb ischemia: implications for clinical trial design.

BACKGROUND: Autologous bone marrow-derived stem cells have been ascribed an important therapeutic role in No-Option Critical limb Ischemia (NO-CLI). One primary endpoint for evaluating NO-CLI therapy is major amputation (AMP), which is usually combined with mortality for AMP-free survival (AFS). Only a trial which is double blinded can eliminate physician and patient bias as to the timing and reason for AMP. We examined factors influencing AMP in a prospective double-blinded pilot RCT (2:1 therapy to control) of 48 patients treated with site of service obtained bone marrow cells (BMAC) as well as a systematic review of the literature. METHODS: Cells were injected intramuscularly in the CLI limbs as either BMAC or placebo (peripheral blood). Six month AMP rates were compared between the two arms. Both patient and treating team were blinded of the assignment in follow-up examinations. A search of the literature identified 9 NO-CLI trials, the control arms of which were used to determine 6 month AMP rates and the influence of tissue loss. RESULTS: Fifteen amputations occurred during the 6 month period, 86.7% of these during the first 4 months. One amputation occurred in a Rutherford 4 patient. The difference in amputation rate between patients with rest pain (5.6%) and those with tissue loss (46.7%), irrespective of treatment group, was significant (p = 0.0029). In patients with tissue loss, treatment with BMAC demonstrated a lower amputation rate than placebo (39.1% vs. 71.4%, p = 0.1337). The Kaplan-Meier time to amputation was longer in the BMAC group than in the placebo group (p = 0.067). Projecting these results to a pivotal trial, a bootstrap simulation model showed significant difference in AFS between BMAC and placebo with a power of 95% for a sample size of 210 patients. Meta-analysis of the literature confirmed a difference in amputation rate between patients with tissue loss and rest pain. CONCLUSIONS: BMAC shows promise in improving AMP-free survival if the trends in this pilot study are validated in a larger pivotal trial. The difference in amp rate between Rutherford 4 & 5 patients suggests that these patients should be stratified in future RCTs.

A randomized, open-label pilot study comparing desirudin and argatroban in patients with suspected heparin-induced thrombocytopenia with or without thrombosis: PREVENT-HIT Study.

Because of an extreme risk for thromboemboli, patients with suspected heparin-induced thrombocytopenia (HIT) require immediate initiation of an alternative anticoagulant. The only therapies approved by the Food and Drug Administration require intravenous infusion of expensive direct thrombin inhibitors. This prospective, randomized, open-label, exploratory study compared the clinical and economic utility of subcutaneous desirudin vs argatroban, the most frequently used agent for suspected or immunologically confirmed HIT, with or without thrombosis. Sixteen patients were randomized to treatment with fixed-dose desirudin (15 or 30 mg) every 12 hours or activated partial thromboplastin time-adjusted argatroban by intravenous infusion. Arm A included 8 patients naive to direct thrombin inhibitor therapy, whereas Arm B included 8 patients on argatroban for at least 24 hours before randomization. The primary efficacy measure was the composite of new or worsening thrombosis (objectively documented), amputation, or death. Other end points included major and minor bleeding while on drug therapy, time to platelet count recovery, and pharmacoeconomics. No amputations or deaths occurred. One patient randomized to argatroban had worsening of an existing thrombosis. Major bleeding occurred in 2 patients on argatroban and in none during desirudin treatment. There was 1 minor bleed in each treatment group. The average medication cost per course of treatment was $1688 for desirudin and $8250 for argatroban. Desirudin warrants further study as a potentially cost-effective alternative to argatroban in patients with suspected HIT.

Disparity in outcomes of surgical revascularization for limb salvage: race and gender are synergistic determinants of vein graft failure and limb loss.

BACKGROUND: Vein bypass surgery is an effective therapy for atherosclerotic occlusive disease in the coronary and peripheral circulations; however, long-term results are limited by progressive attrition of graft patency. Failure of vein bypass grafts in patients with critical limb ischemia results in morbidity, limb loss, and additional resource use. Although technical factors are known to be critical to the success of surgical revascularization, patient-specific risk factors are not well defined. In particular, the relationship of race/ethnicity and gender to the outcomes of peripheral bypass surgery has been controversial. METHODS AND RESULTS: We analyzed the Project of Ex Vivo Vein Graft Engineering via Transfection III (PREVENT III) randomized trial database, which included 1404 lower extremity vein graft operations performed exclusively for critical limb ischemia at 83 North American centers. Trial design included intensive ultrasound surveillance of the bypass graft and clinical follow-up to 1 year. Multivariable modeling (Cox proportional hazards and propensity score) was used to examine the relationships of demographic variables to clinical end points, including perioperative (30-day) events and 1-year outcomes (vein graft patency, limb salvage, and patient survival). Final propensity score models adjusted for 16 covariates (including type of institution, technical factors, selected comorbidities, and adjunctive medications) to examine the associations between race, gender, and outcomes. Among the 249 black patients enrolled in PREVENT III, 118 were women and 131 were men. Black men were at increased risk for early graft failure (hazard ratio [HR], 2.832 for 30-day failure; 95% confidence interval [CI], 1.393 to 5.759; P=0.0004), even when the analysis was restricted to exclude high-risk venous conduits. Black patients experienced reduced secondary patency (HR, 1.49; 95% CI, 1.08 to 2.06; P=0.016) and limb salvage (HR, 2.02; 95% CI, 1.27 to 3.20; P=0.003) at 1 year. Propensity score models demonstrate that black women were the most disadvantaged, with an increased risk for loss of graft patency (HR, 2.02 for secondary patency; 95% CI, 1.27 to 3.20; P=0.003) and major amputation (HR, 2.38; 95% CI, 1.18 to 4.83; P=0.016) at 1 year. Perioperative mortality and 1-year mortality were similar across race/gender groups. CONCLUSIONS: Black race and female gender are risk factors for adverse outcomes after vein bypass surgery for limb salvage. Graft failure and limb loss are more common events in black patients, with black women being a particularly high-risk group. These data suggest the possibility of an altered biological response to vein grafting in this population; however, further studies are needed to determine the mechanisms underlying these observed disparities in outcome.

Follow-up after carotid endarterectomy and stenting: What to look for and why.

Duplex ultrasound testing after open or endovascular extracranial carotid artery interventions is a clinical practice guideline with a strong recommendation from the Society for Vascular Surgery. Neurologic outcomes are improved by the recognition of repair site stenosis or atherosclerotic disease progression in the unoperated carotid artery. The benefit of surveillance outweighs its risk because duplex testing is free of complications and accurate in the detection of internal carotid artery (ICA) stenosis or occlusion. Surveillance for >70% ICA stenosis is recommended within 30 days of the procedure, then every 6 months for 2 years, and annually thereafter. Repair site and contralateral ICA stenosis classification should be based on angle-corrected pulsed Doppler measurements of peak systolic velocity (PSV), end-diastolic velocity (EDV), and the ratio of PSV at the stenosis to a proximal, nondiseased common carotid artery (CCA) segment (ICA/CCA ratio). Interpretation criteria of PSV >300 cm/s, EDV >125 cm/s, and ICA/CCA ratio >4 predicts >70% repair site stenosis. Endovascular intervention is recommended for a carotid repair site stenosis based on the occurrence of an ipsilateral neurologic event and appropriate anatomy for angioplasty. For asymptomatic restenosis, intervention is based on stenosis progression to elevated PSV and EDV >70% stenosis threshold values and the patient is deemed high risk for stroke due to contralateral ICA occlusion or incomplete functional patency of the circle of Willis.

Aortic aneurysm screening using duplex ultrasound: Choosing wisely who to examine.

The noninvasive vascular laboratory plays a critical role in screening patients at risk for development of abdominal aortic aneurysm (AAA). One-time duplex ultrasound screening reduces aneurysm-related mortality due to rupture and is cost-effective. Population screening based on AAA risk factors is recommended, as it allows for proactive, elective repair of aneurysms at risk for rupture, and surveillance of smaller aneurysms for enlargement. Utilization of societal screening guidelines, such as those published by the Society for Vascular Surgery, can be employed by vascular laboratories to justify individual patient screening, aid primary care physicians to refer patients for testing, and encourage integrated medical health care systems to build prompts in patient electronic health records to ensure compliance with a AAA screening program. Risk factors for developing AAA, that is, age older than 65 years, male sex, family history, and a smoking history of >100 cigarettes, should be used to recommend patient screening, including for women and other elderly (older than 75 years) patients who fall outside of professional societal guidelines.

Regional antibiotic delivery for the treatment of experimental prosthetic graft infections.

OBJECTIVES: To evaluate the efficacy of antibiotic-impregnated polymethylmethacrylate (PMMA) beads in eradication of an arterial prosthetic graft methicillin-resistant Staphylococcus aureus (MRSA) biofilm in an experimental animal model. METHODS: Forty rats underwent subcutaneous implantation of a MRSA-colonized arterial polytetrafluoroethylene (PTFE) 1 x 1 cm wafer on the back. The effect of regional antibiosis produced by antibiotic PMMA bead placement adjacent to the infected PTFE wafer was determined using four 10-animal study groups: control (no antibiotic), PMMA bead with no antibiotic, PMMA bead with 10% vancomycin, and PMMA bead with 10% daptomycin. After 3 d, the PTFE wafers were explanted and quantitative biofilm cultures, expressed as colony-forming units (CFU) per graft wafer, performed using real-time polymerase chain reaction to assess MRSA eradication. No systemic antibiotic was administered. Bioassays of antibiotic bead bacteriocidal were performed by measuring zone of inhibition diameters on MRSA colonized agar culture plates prior to and following graft explantation. RESULTS: All animal tolerated implantation of the MRSA-infected PTFE wafer and survived the 3 d until graft explantation. Quantitative biofilm cultures demonstrated a significant decrease (P < 0.01) in MRSA CFUs present on the PTFE wafer surfaces in the presence of both the vancomycin- and daptomycin-impregnated beads compared to controls and plain PMMA beads. Both vancomycin and daptomycin PMMA beads retained antibacterial activity after 3 d of implantation with decrease in zones of inhibition of 15% and 45%, respectively. CONCLUSIONS: Regional antibiotic delivery using an antibiotic-impregnated PMMA bead reduced the bacterial biofilm concentration in experimental subcutaneous pocket model of vascular surgical site infection. The delivery of antibiotics via a PMMA bead may be a useful adjunct in the treatment of vascular surgical site infection.

Vascular surgery resident education and hands-on training in vascular laboratory testing.

Diagnostic testing performed in the noninvasive vascular laboratory is a cornerstone of care for patients with suspected or known vascular disease. The Society for Vascular Surgery has mandated that vascular surgery resident training include mentored experience in performing vascular laboratory testing and interpreting its results. The trainee should be experienced with vascular laboratory instrumentation and testing protocols, be knowledgeable in ultrasound imaging of vascular anatomy, and be competent to classify disease severity relevant to the study indication. The scope of test interpretation should include peripheral arterial, peripheral venous, cerebrovascular, and visceral abdominal testing using duplex ultrasound supplemented by indirect physiologic testing for peripheral arterial and venous disease. The emergence of endovascular therapy has expanded duplex ultrasound applications in the areas of screening, procedural imaging, and surveillance following intervention. Pre-procedure testing to assess disease location and severity, and vein mapping for dialysis access or extremity bypass grafting provide important patient-specific information that can reduce the need for more invasive vascular imaging. It is recommended that trainees acquire the hand-on skills to perform duplex testing in vascular clinic and inpatient sites, such as the emergency department and operating room. Training programs should have a structured vascular laboratory curriculum that documents annual educational milestones that encompass both test interpretation aptitude and hands-on duplex scanning skills. Before completion of training, the resident should acquire documented experience in test interpretation sufficient to take the Physician Vascular Interpretation examination, which is required for American Board of Surgery certification as a vascular surgeon.

Risk stratification in critical limb ischemia: derivation and validation of a model to predict amputation-free survival using multicenter surgical outcomes data.

BACKGROUND: Patients with critical limb ischemia (CLI) are a heterogeneous population with respect to risk for mortality and limb loss, complicating clinical decision-making. Endovascular options, compared with bypass, offer a tradeoff between reduced procedural risk and inferior durability. Risk stratified data predictive of amputation-free survival (AFS) may improve clinical decision making and allow for better assessment of new technology in the CLI population. METHODS: This was a retrospective analysis of prospectively collected data from patients who underwent infrainguinal vein bypass surgery for CLI. Two datasets were used: the PREVENT III randomized trial (n = 1404) and a multicenter registry (n = 716) from three distinct vascular centers (two academic, one community-based). The PREVENT III cohort was randomly assigned to a derivation set (n = 953) and to a validation set (n = 451). The primary endpoint was AFS. Predictors of AFS identified on univariate screen (inclusion threshold, P < .20) were included in a stepwise selection Cox model. The resulting five significant predictors were assigned an integer score to stratify patients into three risk groups. The prediction rule was internally validated in the PREVENT III validation set and externally validated in the multicenter cohort. RESULTS: The estimated 1-year AFS in the derivation, internal validation, and external validation sets were 76.3%, 72.5%, and 77.0%, respectively. In the derivation set, dialysis (hazard ratio [HR] 2.81, P < .0001), tissue loss (HR 2.22, P =.0004), age >or=75 (HR 1.64, P = .001), hematocrit or=8 [8.8% of cohort]). Stratification of the patients, in each dataset, according to risk category yielded three significantly different Kaplan-Meier estimates for 1-year AFS (86%, 73%, and 45% for low, medium, and high risk groups, respectively). For a given risk category, the AFS estimate was consistent between the derivation and validation sets. CONCLUSION: Among patients selected to undergo surgical bypass for infrainguinal disease, this parsimonious risk stratification model reliably identified a category of CLI patients with a >50% chance of death or major amputation at 1 year. Calculation of a "PIII risk score" may be useful for surgical decision making and for clinical trial designs in the CLI population.

Efficacy of duplex ultrasound surveillance after infrainguinal vein bypass may be enhanced by identification of characteristics predictive of graft stenosis development.

OBJECTIVE: Controversy regarding the efficacy of duplex ultrasound surveillance after infrainguinal vein bypass led to an analysis of patient and bypass graft characteristics predictive for development of graft stenosis and a decision of secondary intervention. METHODS: Retrospective analysis of a contemporary, consecutive series of 353 clinically successful infrainguinal vein bypasses performed in 329 patients for critical (n = 284; 80%) or noncritical (n = 69; 20%) limb ischemia enrolled in a surveillance program to identify and repair duplex-detected graft stenosis. Variables correlated with graft stenosis and bypass repair included: procedure indication, conduit type (saphenous vs nonsaphenous vein; reversed vs nonreversed orientation), prior bypass graft failure, postoperative ankle-brachial index (ABI) < 0.85, and interpretation of the first duplex surveillance study as "normal" or "abnormal" based on peak systolic velocity (PSV) and velocity ratio (Vr) criteria. RESULTS: Overall, 126 (36%) of the 353 infrainguinal bypasses had 174 secondary interventions (endovascular, 100; surgery, 74) based on duplex surveillance; resulting in 3-year Kaplan-Meier primary (46%), assisted-primary (80%), and secondary (81%) patency rates. Characteristics predictive of duplex-detected stenosis leading to intervention (PSV: 443 +/- 94 cm/s; Vr: 8.6 +/- 9) were: "abnormal" initial duplex testing indicating moderate (PSV: 180-300 cm/s, Vr: 2-3.5) stenosis (P < .0001), non-single segment saphenous vein conduit (P < .01), warfarin drug therapy (P < .01), and redo bypass grafting (P < .001). Procedure indication, postoperative ABI level, statin drug therapy, and vein conduit orientation were not predictive of graft revision. The natural history of 141 (40%) bypasses with an abnormal first duplex scan differed from "normal" grafts by more frequent (51% vs 24%, P < .001) and earlier (7 months vs 11 months) graft revision for severe stenosis and a lower 3-year assisted primary patency (68% vs 87%; P < .001). In 52 (15%) limbs, the bypass graft failed and 20 (6%) limbs required amputation. CONCLUSIONS: The efficacy of duplex surveillance after infrainguinal vein bypass may be enhanced by modifying testing protocols, eg, rigorous surveillance for "higher risk" bypasses, based on the initial duplex scan results and other characteristics (warfarin therapy, non- single segment saphenous vein conduit, redo bypass) predictive for stenosis development.

Vascular surgical site infection: risk factors and preventive measures.

Surgical-site infection (SSI) after arterial intervention is the most common nosocomial vascular infection and an important cause of postoperative morbidity. Its prevention requires the vascular surgeon to be cognizant of its changing epidemiology, patient risk factors, and effective measures to reduce its incidence. The majority of vascular SSIs are caused by Gram-positive bacteria, and methicillin-resistant Staphylococcus aureus has emerged as the prevalent pathogen, now involved in more than one-third of cases. Nasal carriage of methicillin-sensitive or methicillin-resistant S. aureus strains, recent hospitalization, failed arterial reconstruction, and presence of a groin incision, are major risk factors for developing vascular SSI. Overall, the vascular SSI rate is higher than predicted by Center for Disease Control National Nosocomial Infections Surveillance risk category system, and ranges from 1% to 2% after open or endovascular aortic interventions to as high as 10% to 20% after lower-limb bypass grafting procedures. Use of preoperative measures to reduce S. aureus nasal and skin colonization in conjunction with appropriate, bactericidal antibiotic prophylaxis, meticulous wound closure, and postoperative care to optimize patient host defense regulation mechanisms (temperature, oxygenation, blood sugar) can minimize SSI occurrence.

Expected flow parameters within hemodialysis access and selection for remedial intervention of nonmaturing conduits.

BACKGROUND: Persistent poor patency rates of arteriovenous fistulae and bridge grafts for dialysis access prompted us to investigate whether flow parameters derived from an initial postconstruction, precannulation duplex study could predict access longevity or direct remedial procedures to salvage nonmaturing conduits. METHODS: We analyzed 125 consecutive dialysis access conduits (34 forearm fistulae, 53 arm fistulae, 38 prosthetic bridge grafts, 108 patients, 82 male/26 female, average age 58 years) over the past 5 years having early (2 to 8 weeks) duplex scanning done prior to attempted hemodialysis cannulation. Velocity waveforms were recorded in the arterial inflow, arterial and venous anastomoses, mid-conduit, and in the venous outflow with averaging of volume flow rate (product of average velocity and cross-sectional area) measured at 3 mid-conduit sites. Conduits were deemed "adequate" for dialysis cannulation or "nonmaturing" by the presence of detected high-grade stenoses (peak systolic velocity >400cm/s, velocity ratio >3, and minimal diameter <2 to 3 mm) and subjected to remedial interventions (endovascular or open). Subsequent access function for hemodialysis use and late patency were recorded and correlated with early duplex findings. RESULTS: Average flow rates (forearm fistula 784 +/- 623 mL/min, arm fistula 1400 +/- 850, bridge graft 1270 +/- 604) and mid-conduit peak-systolic velocities (215 +/- 214 cm/s forearm fistula vs 312 +/- 194 arm fistula) differed between conduit type and location. Remedial interventions were needed in 10 (26%) bridge grafts and 18 (21%) fistulae "nonmaturing" due to occlusive lesions. Conduit flow rates differentiated "nonmaturing" (606 +/- 769 mL/min) and "maturing" (1140 +/- 857) fistulae (P = .01). A threshold conduit flow rate of 800 mL/min better discriminated failing and functional fistulae and bridge grafts (accuracy 77%) than a flow rate greater or less than 500 mL/min (accuracy 67%). Remedial interventions doubled average flow rates of "nonmaturing" accesses (from 605 to 1159 mL/min) to values similar to "mature, functional" conduits (1374 mL/min) and facilitated a mean duration of patency (12.9 months) equivalent to conduits not needing remedial interventions (11.5 months). CONCLUSIONS: Duplex-derived hemodynamic parameters characterized early dialysis access conduit function, prognosticated access patency, guided necessary remedial interventions, and facilitated favorable access longevity.

Evolving microbiology and treatment of extracavitary prosthetic graft infections.

The authors report the microbiology and outcomes following an individualized treatment algorithm for extracavitary (EC) prosthetic graft infection, including the use of graft preservation and in situ graft replacement techniques. A retrospective 8-year review of 87 patients treated for EC prosthetic graft infections was carried out. The treatment algorithm included culture-specific antibiotic therapy, surgical site debridement with antibiotic bead placement, selected graft preservation with muscle flap coverage, or graft excision with in situ conduit replacement. Outcomes measured included death, limb loss, and recurrent infection. It was found that present-day management of EC prosthetic graft infections is associated with lower mortality and morbidity despite changes in microbiology and the increased application of graft preservation and in situ grafting treatments.

The diabetic foot: Pathophysiology, evaluation, and treatment.

The pathophysiology of the diabetic foot ulcer and soft-tissue infection is due to neuropathy, trauma, and, in many patients, concomitant peripheral artery occlusive disease. Diabetic neuropathy results in foot deformity, leading to increased skin pressure with walking. Once a foot ulcer develops, the limb is at high risk for invasive infection and, when combined with peripheral artery occlusive disease, the patient should be considered to have critical limb ischemia. A multidisciplinary approach to care for the diabetic foot is recommended, which includes annual (3-month intervals in high-risk patients) assessments by a primary care physician and referral to a podiatrist and vascular surgeon for diabetics with a foot ulcer for evaluation of foot arterial perfusion and off-loading therapy to reduce plantar skin pressure with walking. When invasive foot infection develops and tissue beneath the fascia is involved, inpatient care is recommended for systemic antibiotic therapy, vascular laboratory testing of artery limb perfusion, and surgical debridement of infected tissue. The goals of treatment are to achieve a healed foot and keep the patient ambulatory.

Surveillance after lower extremity arterial bypass.

The elements of a surveillance program after lower limb bypass grafting to enhance graft patency continue to evolve. Graft evaluation should include clinical assessment for new or changes in limb ischemia symptoms, measurement of ankle or toe systolic pressure, or both, and duplex ultrasound imaging of the bypass graft, which in the early postoperative period is predictive of the subsequent need for bypass graft revision. The natural history of moderate graft stenosis is known, and these lesions can be safely monitored using serial testing to identify progression. The testing frequency should be individualized to the patient, type of arterial bypass, and duplex scan findings. Graft surveillance should focus on the identification and repair of critical stenosis (peak systolic velocity exceeding 300 cm/s, and peak systolic velocity ratio across the stenosis exceeding 3.5) correlating with more than 70% diameter-reducing stenosis. A graft surveillance program should result in a graft failure rate of less than 3% per year.

Duplex ultrasound surveillance can be worthwhile after arterial intervention.

A surveillance program based on duplex ultrasound testing after peripheral arterial intervention can increase long-term patency by identifying and by repairing clinical significant lesions. Its successful application requires numerous conditions regarding pathobiology of arterial repair failure and its consequences, arterial testing expertise, and durability of secondary procedures used to repair duplex-detected lesions. The methodology of surveillance should be tailored to the type of arterial intervention. Clinical reports on the efficacy of duplex ultrasound surveillance have supported its routine use, but controversy of cost-effectiveness remains. Duplex surveillance will decrease procedural primary patency, but when successful, the primary-assisted and secondary patency rates should be significantly higher than the rates when no surveillance was performed. An examination of the primary, primary-assisted, and secondary patency rates of an arterial procedure will indicate the benefit (or lack of benefit) of a surveillance program and the appropriateness of the threshold criteria used for secondary interventions.

Risk factors for recurrent hemorrhage after successful mesenteric arterial embolization.

The objective of this study was to describe the risk factors and to determine the outcomes after recurrent gastrointestinal hemorrhage after successful mesenteric arterial embolization A retrospective analysis was undertaken of a single-center experience with mesenteric arterial embolization performed for gastrointestinal hemorrhage over a 5-year period. Statistical analyses including Student's t test and Fisher's exact test were used to compare results. For the years 2001 through 2005, 36 patients (10 women; average age, 60.8 years) underwent 37 technically successful mesenteric embolizations for acute gastrointestinal hemorrhage. Two (5.4%) cases required surgical intervention for cessation of hemorrhage, and six (16.2%) patients died during their hospitalization after technically successful embolization. Nine (24.3%) patients experienced in-hospital rehemorrhage, and of these, five (55.6%) died. Risk factors for rehemorrhage included intra-abdominal malignancy (P < 0.05), transfusion requirement greater than 10 units before angiography (P < 0.05), and the source of hemorrhage other than solitary gastroduodenal artery hemorrhage (P < 0.05). The failure of initial embolization was associated with an increased incidence of death (55.6% vs 5.0%; P < 0.05) and operative intervention to cease hemorrhage (P < 0.05). The failure of technically successful mesenteric embolization is not uncommon and is associated with identifiable risk factors. Risk factor awareness should assist in patient selection for and timing of mesenteric embolization.