Daniel M. Ihnat

Vein diameter is the major predictor of fistula maturation

OBJECTIVES Preoperative duplex ultrasound mapping of veins and arteries has been widely advocated to maximize the creation of native arteriovenous fistula (AVF) for hemodialysis access, but reliable diameter criteria have not been established. We sought to determine patient and anatomic variables predictive of fistula maturation in patients receiving their initial permanent hemodialysis access. METHODS All patients undergoing dialysis access creation from January 2003 to June 2007 were retrospectively reviewed. We analyzed fistula type and functional maturation rates (Society for Vascular Surgery [SVS] reporting standards) based on patient characteristics and findings on physical examination, preoperative vein mapping studies, or venography. Maturation and patency rates were determined by Kaplan Meier analysis. The following factors were analyzed: age, race, gender, body-mass index (BMI), fistula site, preoperative duplex vein diameter, diabetes, hyperlipidemia, HTN, prior central catheter placement, HIV, and history of IV drug abuse. RESULTS From January 2003 to June 2007, 298 vascular access procedures were performed. One hundred ninety-five (65%) were initial hemodialysis access procedures, among which a native AVF was created in 185 (95%); 158 patients with posterior radiocephalic AVF (PRCAVF, n = 24), wrist radiocephalic AVF (WRCAVF, n = 72), or brachiocephalic AVF (BCAVF, n = 62) had adequate follow-up and were included in the analysis. PRCAVF, WRCAVF, and BCAVF had 54%, 66%, and 81% maturation rates, respectively. Both the type of fistula type (P = .032) and vein size (P = .002) significantly affected maturation by univariate analysis. In contrast, by multivariate logistic regression analysis, vein diameter was the sole independent predictor of fistula functional maturation (P = .002). CONCLUSION In this series of 158 patients undergoing initial hemodialysis access creation, native AVF creation was performed in 95%. In contrast to previous reports, age, gender, diabetes, and BMI had no significant effect on functional maturation. By multivariate logistic regression analysis, vein diameter was the sole independent predictor of functional fistula maturation.

Contemporary outcomes after superficial femoral artery angioplasty and stenting: The influence of TASC classification and runoff score

OBJECTIVE A recent randomized trial suggested nitinol self-expanding stents (SES) were associated with reduced restenosis rates compared with simple percutaneous transluminal angioplasty (PTA). We evaluated our results with superficial femoral artery (SFA) SES to determine whether TransAtlantic InterSociety Consensus (TASC) classification, indication for intervention, patient risk factors, or Society of Vascular Surgery (SVS) runoff score correlated with patency and clinical outcome, and to evaluate if bare nitinol stents or expanded polytetrafluoroethylene (ePTFE) covered stent placement adversely impacts the tibial artery runoff. METHODS A total of 109 consecutive SFA stenting procedures (95 patients) at two university-affiliated hospitals from 2003 to 2006 were identified. Medical records, angiographic, and noninvasive studies were reviewed in detail. Patient demographics and risk factors were recorded. Procedural angiograms were classified according to TASC Criteria (I-2000 and II-2007 versions) and SVS runoff scores were determined in every patient; primary, primary-assisted, secondary patency, and limb salvage rates were calculated. Cox proportional hazard model was used to determine if indication, TASC classification, runoff score, and comorbidities affected outcome. RESULTS Seventy-one patients (65%) underwent SES for claudication and 38 patients (35%) for critical limb ischemia (CLI). Average treatment length was 15.7 cm, average runoff score was 4.6. Overall 36-month primary, primary-assisted, and secondary rates were 52%, 64%, and 59%, respectively. Limb salvage was 75% in CLI patients. No limbs were lost following interventions in claudicants (mean follow-up 16 months). In 24 patients with stent occlusion, 15 underwent endovascular revision, only five (33%) ultimately remained patent (15.8 months after reintervention). In contrast, all nine reinterventions for in-stent stenosis remained patent (17.8 months). Of 24 patients who underwent 37 endovascular revisions for either occlusion or stenosis, eight (35%) had worsening of their runoff score (4.1 to 6.4). By Cox proportional hazards analysis, hypertension (hazard ratio [HR] 0.35), TASC D lesions (HR 5.5), and runoff score > 5 (HR 2.6) significantly affected primary patency. CONCLUSIONS Self-expanding stents produce acceptable outcomes for treatment of SFA disease. Poorer patency rates are associated with TASC D lesions and poor initial runoff score; HTN was associated with improved patency rates. Stent occlusion and in-stent stenosis were not entirely benign; one-third of patients had deterioration of their tibial artery runoff. Future studies of SFA interventions need to stratify TASC classification and runoff score. Further evaluation of the long-term effects of SFA stenting on tibial runoff is needed.

Treatment of patients with venous thromboembolism and malignant disease: Should vena cava filter placement be routine?

PURPOSE It has been proposed that inferior vena cava filter placement should be the initial treatment of deep venous thrombosis (DVT) or pulmonary embolus (PE) in patients with coexisting malignant disease. We have chosen instead to selectively place filters only in patients with either a contraindication to anticoagulation therapy or a subsequent complication from anticoagulation therapy. The treatment efficacy and mortality rates in patients with concomitant malignant disease and venous thromboembolism using this approach was determined. METHODS We retrospectively reviewed all patients at our institution with malignant disease in whom venous thromboembolism developed between August 1991 through August 1996 and identified 166 patients with PE (n = 8), DVT (n = 147), and DVT/PE (n = 11). Of these patients, 138 (83.1%) were initially treated with anticoagulation therapy, and 28 (16.9%) had primary filter placement because of contraindications to anticoagulation therapy (10 for intracranial tumors, 11 for recent or upcoming operations, 6 for recent hemorrhage, and 1 for a malignant bloody pericardial effusion). RESULTS Thirty-two (23%) of the 138 patients who initially underwent anticoagulation therapy subsequently required a filter for the following reasons: bleeding (n = 15, 10.9%); recurrent thromboembolism (n = 6, 4.3%); heparin-induced thrombocytopenia (n = 1, 0.7%); and perceived high risk for bleeding with continued anticoagulation therapy (n = 11, 8%). Both bleeding and recurrent thromboembolism developed in 1 patient. Sixty patients (36%) received filters. No major technical complications occurred from filter placement. Major recurrent thromboembolic complications developed in 10 patients: DVT (n = 6, 10%), PE (n = 2, 3.3%), inferior vena cava thrombosis and phlegmasia cerulea dolens (n = 1, 1.7%), superior vena cava thrombosis (n = 1, 1.7%). Venous gangrene developed in 1 patient with DVT. The 1-year actuarial survival rates for patients treated with filter and anticoagulation therapy were 35% and 38%, respectively (P = NS). CONCLUSION In summary, our experience suggests that 64% of patients with malignant disease and venous thromboembolism are effectively treated with anticoagulation alone; 17% require primary filter placement for standard indications, and an additional 19% require subsequent filter placement because of complications (primarily bleeding) or failure of anticoagulation therapy. Although technical complications of filter placement are low, serious life-threatening or limb-threatening thromboembolic complications developed in 17% of patients. Survival was poor in all patients, regardless of treatment. These data support a conservative approach of routine anticoagulation therapy with selective filter placement.

Comparison of the effects of open and endovascular aortic aneurysm repair on long-term renal function using chronic kidney disease staging based on glomerular filtration rate

OBJECTIVE It has been suggested that endovascular aneurysm repair (EVAR) in concert with serial contrast-enhanced computed tomography (CT) surveillance adversely impacts renal function. Our primary objectives were to assess serial renal function in patients undergoing EVAR and open repair (OR) and to evaluate the relative effects of method of repair on renal function. METHODS A thorough retrospective chart review was performed on 223 consecutive patients (103 EVAR, 120 OR) who underwent abdominal aortic aneurysm (AAA) repair. Demographics, pertinent risk factors, CT scan number, morbidity, and mortality were recorded in a database. Baseline, 30- and 90-day, and most recent glomerular filtration rate (GFR) were calculated. Mean GFR changes and renal function decline (using Chronic Kidney Disease [CKD] staging and Kaplan-Meier plot) were determined. EVAR and OR patients were compared. CKD prevalence (>or=stage 3, National Kidney Foundation) was determined before repair and in longitudinal follow-up. Observed-expected (OE) ratios for CKD were calculated for EVAR and OR patients by comparing observed CKD prevalence with the expected, age-adjusted prevalence. RESULTS The only baseline difference between EVAR and OR cohorts was female gender (4% vs 12%, P = .029). Thirty-day GFR was significantly reduced in OR patients (P = .047), but it recovered and there were no differences in mean GFR at a mean follow-up of 23.2 months. However, 18% to 39% of patients in the EVAR and OR groups developed significant renal function decline over time depending on its definition. OE ratios for CKD prevalence were greater in AAA patients at baseline (OE 1.28-3.23, depending upon age group). During follow-up, the prevalence and severity of CKD increased regardless of method of repair (OE 1.8-9.0). Deterioration of renal function was independently associated with age >70 years in all patients (RR 2.92) and performance of EVAR compared with OR (RR 3.5) during long-term follow-up. CONCLUSIONS Compared with EVAR, OR was associated with a significant but transient fall in GFR at 30 days. Renal function decline after AAA repair was common, regardless of method, especially in patients >70 years of age. However, the renal function decline was significantly greater by Kaplan-Meier analysis in EVAR than OR patients during long-term follow-up. More aggressive strategies to monitor and preserve renal function after AAA repair are warranted.

Temporary arterial shunts to maintain limb perfusion after arterial injury: an animal study.

BACKGROUND Temporary shunt placement can quickly restore perfusion after extremity arterial injury. This study examined the adequacy of limb blood flow with shunt use, non-heparin-bonded shunt patency over prolonged periods, and the safety of this technique. METHODS Common iliac arteries were divided and 4.0-mm Silastic Sundt shunts placed in 16 anesthetized pigs. Eight (group I) had shunts placed immediately; eight others (group II) were shunted after an hour of limb ischemia and hemorrhagic shock. Physiologic parameters and femoral artery blood flow in both hindlimbs were continuously monitored. Limb lactic acid generation, oxygen utilization, and hematologic and metabolic effects were serially evaluated for 24 hours. RESULTS Shunts remained patent in 13 of 16 pigs. Shunts thrombosed in two group I animals because of technical errors, but functioned well after thrombectomy and repositioning. Patency could not be maintained in one animal that died from shock. Flow in group I shunted limbs was 57 (+/-11 SD) % of control. For group II animals in shock, shunted limb flow initially averaged 46 +/- 15% of control, but 4 hours after shunt placement, the mean limb blood flow was the same as in group I. Increased oxygen extraction compensated for the lower flow. Lactic acid production was not increased in comparison to control limbs. CONCLUSION Shunts provided adequate flow in this model of extremity trauma. Correctly placed shunts stayed patent for 24 hours, without anticoagulation, if shunt placement followed resuscitation.

The use of a thrombus-specific ultrasound contrast agent to detect thrombus in arteriovenous fistulae

RATIONALE AND OBJECTIVES To evaluate the use of a new thrombus-specific ultrasound contrast agent, MRX-408, in the ultrasonic detection of thrombus in arteriovenous (AV) fistulae. METHODS Six purpose-bred mongrels with two AV fistulae each were imaged with gray-scale ultrasound 7 weeks after graft implantation before and after the intravenous bolus injection of MRX-408 (a GPIIb receptor-targeted ultrasound contrast agent). Pre- and postcontrast videotaped segments were randomized and reviewed by four radiologists blinded to the presence of thrombus in the grafts. RESULTS After the use of MRX-408, there was improved visualization of thrombus within the grafts (P < 0.0001). This was due to the enhancement of the thrombus (P < 0.0001). The improved visualization and contrast enhancement were more marked in the grafts that contained thrombus nonhyperechoic to surrounding soft tissues. CONCLUSIONS MRX-408 demonstrated better visualization of thrombus within AV fistulae. This was shown in both patent and occluded grafts. These results are encouraging and suggest that this contrast agent merits further development.

Current Assessment of Endovascular Therapy for Infrainguinal Arterial Occlusive Disease in Patients with Diabetes

Endovascular therapy (EVT) has increasingly become the initial clinical option for treatment of lower extremity peripheral arterial disease (PAD), not only for patients with claudication, but also for those with critical limb ischemia. Despite this major clinical practice paradigm shift, the outcomes of EVT for PAD are difficult to evaluate and compare with established surgical benchmarks because of the lack of prospective, randomized trials, incomplete characterization of indications for intervention, mixing of arterial segments and extent of disease treated, the multiplicity of EVT techniques used, the exclusion of early treatment failures, crossover to open bypass during follow-up, and the frequent lack of intermediate and long-term patency and limb salvage rates in life-table format. These data limitations are especially problematic when one tries to assess the outcome of EVT in patients with diabetes. The purpose of the present report is to succinctly review and objectively analyze available data regarding the results of EVT in patients with diabetes.

The correlation of early flow disturbances with the development of infrainguinal graft stenosis: A 10-year study of 341 autogenous vein grafts

PURPOSE Although duplex surveillance of infrainguinal bypass grafts is widely accepted, the optimal frequency and intensity of graft surveillance remains controversial. Earlier reports have suggested that grafts can be stratified into high-risk and low-risk groups based on the presence or absence of early graft flow disturbances. The purpose of this study was to provide long-term data in determining whether early graft flow disturbances detected by means of duplex scanning can predict the development of intrinsic vein graft stenosis. METHODS We reviewed a series of patients undergoing prospective duplex graft surveillance after autogenous infrainguinal bypass grafting procedures from 1987 to 1997. Patients included in the study underwent at least one duplex scan within 3 months of graft implantation and were observed for a minimum of 6 months. Grafts were categorized as abnormal when a focal flow disturbance with a peak systolic velocity greater than 150 cm/s was identified within 3 months of graft implantation. RESULTS Of 341 vein grafts in 296 patients who met inclusion criteria, 89 grafts (26%) required revision for intrinsic stenosis; the mean follow-up period was 35 months (range, 6 months to 10 years). Early flow disturbances were detected in 84 (25%) grafts. Grafts with early flow disturbances were more likely to ultimately require revision (43% vs 21%; P =. 0001) and required initial revision earlier (8 months vs 16 months; P =.019). Eighty-two percent of initial graft revisions occurred in the first 2 postoperative years; 69% occurred in the first year. However, an annual 2% to 4% incidence of late-appearing graft stenosis persisted during long-term follow-up. An additional 24 patients (7% of grafts) required an inflow or outflow reconstruction. CONCLUSION Grafts with early postoperative flow disturbances detected by means of duplex scanning have nearly three times the incidence of graft-threatening stenosis and an earlier requirement for revision, when compared with normal grafts. This suggests that the biology and etiology of these lesions may differ. These data support not only aggressive efforts to detect early graft lesions to stratify grafts at highest risk, but also continued lifelong graft surveillance to detect late-appearing lesions, inflow and outflow disease progression, and maximize graft patency.

The natural history of duplex-detected stenosis after femoropopliteal endovascular therapy suggests questionable clinical utility of routine duplex surveillance.

OBJECTIVE Duplex ultrasound (DU) surveillance (DUS) criteria for vein graft stenosis and thresholds for reintervention are well established. The natural history of DU-detected stenosis and the threshold criteria for reintervention in patients undergoing endovascular therapy (EVT) of the femoropopliteal system have yet to be determined. We report an analysis of routine DUS after infrainguinal EVT. METHODS Consecutive patients undergoing EVT of the superficial femoral artery (SFA) or popliteal artery were prospectively enrolled in a DUS protocol (≤1 week after intervention, then at 3, 6, and 12 months thereafter). Peak systolic velocity (PSV) and velocity ratio (Vr) were used to categorize the treated artery: normal was PSV <200 cm/s and Vr <2, moderate stenosis was PSV = 200-300 cm/s or Vr = 2-3, and severe stenosis was PSV >300 cm/s or Vr >3. Reinterventions were generally performed for persistent or recurrent symptoms, allowing us to analyze the natural history of DU-detected lesions and to perform sensitivity and specificity analysis for DUS criteria predictive of failure. RESULTS Ninety-four limbs (85 patients) underwent EVT for SFA-popliteal disease and were prospectively enrolled in a DUS protocol. The initial scans were normal in 61 limbs (65%), and serial DU results remained normal in 38 (62%). In 17 limbs (28%), progressive stenoses were detected during surveillance. The rate of thrombosis in this subgroup was 10%. Moderate stenoses were detected in 28 (30%) limbs at initial scans; of these, 39% resolved or stabilized, 47% progressed to severe, and occlusions developed in 14%. Five (5%) limbs harbored severe stenoses on initial scans, and 80% of lesions resolved or stabilized. Progression to occlusion occurred in one limb (20%). The last DUS showed 25 limbs harbored severe stenoses; of these, 13 (52%) were in symptomatic patients and thus required reintervention regardless of DU findings. Eleven limbs (11%) eventually occluded. Sensitivity and specificity of DUS to predict occlusion were 88% and 60%, respectively. CONCLUSIONS DUS does not reliably predict arterial occlusion after EVT. Stenosis after EVT appears to have a different natural history than restenosis after vein graft bypass. EVT patients are more likely to have severe stenosis when they present with recurrent symptoms, in contrast to vein graft patients, who commonly have occluded grafts when they present with recurrent symptoms. The potential impact of routine DU-directed reintervention in patients after EVT is questionable. The natural history of DU-detected stenosis after femoropopliteal endovascular therapy suggests questionable clinical utility of routine DUS.

Infrainguinal Atherectomy: A Retrospective Review of a Single-Center Experience

By decreasing plaque burden, atherectomy provides an alternative to angioplasty and stenting as a means of revascularizing patients with peripheral arterial disease. A new atherectomy device (SilverHawk) has recently been approved by the Food and Drug Administration, but the results with its use are unclear. We analyzed a series of consecutive patients undergoing atherectomy. We retrospectively reviewed the charts of 35 patients undergoing infrainguinal (IF) atherectomy in 38 limbs. The Trans-Atlantic Inter-Society Consensus (TASC) classification and Society of Vascular Surgery runoff scores were calculated. Time to event analysis was performed using Kaplan-Meier estimates. Risk factors affecting patency were analyzed with a multivariate Cox model. Mean patient age was 70 +/- 9.6 years. Indications for intervention were claudication (26%), rest pain (21%), and tissue loss (53%). Femoropopliteal (FP) atherectomy was performed in 68% and tibial atherectomy in 32%. For FP lesions, the TASC distribution was A, 42%; B, 23%; C, 4%; and D, 15%. The average lesion treatment length was 9.4 +/- 10.6 cm (range 1-40), and the runoff score was 5.1 +/- 3.5. For tibial lesions, the TASC distribution was A, 0%; B, 17%; C, 8%; and D, 75%. The average lesion treatment length was 9.2 +/- 6.0 cm (range 2-20), with a runoff score of 5.4 +/- 2.4. A total of 39% of patients had prior IF interventions. Adjunctive angioplasty of the atherectomized lesion was performed in 55% of cases, stenting in 0%, and adjunctive therapy for tandem lesions in 39%. The postoperative ankle-brachial index increased by 0.30 +/- 0.14 and toe pressures increased by 40 +/- 32.4 mm Hg. Mean follow-up was 10 +/- 8 months (range 0.3-23). During the studied period, seven patients required major limb amputation and five open surgical revascularization. Total primary and secondary patency rates were 66% and 70% at 1 year, respectively. Primary and secondary patency rates for FP atherectomy were 68% and 73% at 1 year, respectively. The limb salvage rate was 74% at 6 months. Patients with prior interventions in the atherectomized segment had an almost 10-fold decrease in primary patency. Atherectomy produces acceptable results, similar to those in reported series of conventional balloon angioplasty/stenting. Patients with prior IF interventions had a nearly 10-fold decrease in primary patency. A greater than sixfold decrease in patency rates was noted in patients who underwent simultaneous inflow or outflow procedures, but this finding did not reach statistical significance (p = 0.082). Future studies should focus on cost comparisons with other treatments such as angioplasty and stenting, and prospective randomized trials should be performed to compare these treatment alternatives.