Twenty years of embolization for acute lower gastrointestinal bleeding: a meta-analysis of rebleeding and ischaemia rates

BACKGROUND

Transarterial embolization (TAE) for acute lower gastrointestinal bleeding (LGIB) can be technically challenging due to the compromise between achieving haemostasis and causing tissue ischaemia. The goal of the present study is to determine its technical success, rebleeding, and post-embolization ischaemia rates through meta-analysis of published literature in the last twenty years.

METHODS

PubMed, Embase, and Cochrane Library databases were queried. Technical success, rebleeding, and ischaemia rates were extracted. Baseline characteristics such as author, publication year, region, study design, embolization material, percentage of superselective embolization were retrieved. Subgroup analysis was performed based on publication time and embolization agent.

RESULTS

A total of 66 studies including 2121 patients who underwent embolization for acute LGIB were included. Endoscopic management was attempted in 34.5%. The pooled overall technical success, rebleeding, post-embolization ischaemia rates were 97.0%, 20.7%, and 7.5%, respectively. Studies published after 2010 showed higher technical success rates (97.8% vs 95.2%), lower rebleeding rates (18.6% vs 23.4%), and lower ischaemia rates (7.3% vs 9.7%). Compared to microcoils, NBCA was associated with a lower rebleeding rate (9.3% vs 20.8%) at the expense of a higher post-embolization ischaemia rate (9.7% vs 4.0%). Coagulopathy (P = .034), inotropic use (P = .040), and malignancy (P = .002) were predictors of post-embolization rebleeding. Haemorrhagic shock (P < .001), inotropic use (P = .026), malignancy (P < .001), coagulopathy (P = .002), blood transfusion (P < .001), and enteritis (P = .023) were predictors of mortality. Empiric embolization achieved a similarly durable haemostasis rate compared to targeted embolization (23.6% vs 21.1%) but a higher risk of post-embolization ischaemia (14.3% vs 4.7%).

CONCLUSION

For LGIB, TAE has a favourable technical success rate and low risk of post-embolization ischaemia. Its safety and efficacy profile has increased over the last decade. Compared to microcoils, NBCA seemed to offer a more durable haemostasis rate at the expense of higher ischaemia risk. Due to the heterogeneity of currently available evidence, future prospective and comparative studies are warranted.

ADVANCES IN KNOWLEDGE

(1) Acute LGIB embolization demonstrate a high technical success rate with acceptable rate of rebleeding and symptomatic ischaemia rates. Most ischaemic stigmata discovered during routine post-embolization colonoscopy were minor. (2) Although NBCA seemed to offer a more durable haemostasis rate, it was also associated with a higher risk of ischaemia compared to microcoils. (3) Coagulopathy, malignant aetiology, and inotropic use were predictors of rebleeding and mortality. (4) Routine post-embolization endoscopy to assess for ischaemia is not indicated.

Preliminary Experience with a Low-Profile High-Density Braid Occluder for Transcatheter Embolization of Pulmonary Arteriovenous Malformations

This brief report describes safety, technical feasibility, and early treatment effectiveness of the low-profile braided occluder (LOBO; Okami Medical, San Diego, Caliornia) for embolization of 9 pulmonary arteriovenous malformations (PAVMs) in 4 patients (3 female and 1 male; age range: 33 to 63 years; 3 patients showed positive results for hereditary hemorrhagic telangiectasia genes). A total of 10 occluders were deployed in 10 vessels (median treated vessel diameters, 3 and 4 mm for LOBO-3 and LOBO-5 groups, respectively). All devices were successfully deployed into the feeder pulmonary arteries, achieving complete cessation of flow. There were no severe adverse events or device migrations. Available short-term follow-up computed tomography (6 PAVMs: median, 7 months; range, 1.5-7 months) demonstrated complete occlusion without persistence or recanalization. The early experience of embolization of PAVMs using a low-profile braided occluder showed it to be safe and effective. Further studies with larger cohorts and longer follow-up periods are warranted.

Transarterial interventions in civilian gunshot wound injury: experience from a level-1 trauma center

PURPOSE

To assess the effectiveness of trans-arterial vascular interventions in treatment of civilian gunshot wounds (GSW).

MATERIALS AND METHODS

A retrospective review was performed at a level-1 trauma center to include 46 consecutive adults admitted due to GSW related hemorrhage and treated with endovascular interventions from July 2018 to July 2022. Patient demographics and procedural metrics were retrieved. Primary outcomes of interest include technical success and in-hospital mortality. Factors of mortality were assessed using a logistic regression model.

RESULTS

Twenty-one patients were brought to the endovascular suite directly (endovascular group) from the trauma bay and 25 patients after treatment in the operating room (OR group). The OR group had higher hemodynamic instability (48.0% vs 19.0%, p = 0.040), lower hemoglobin (12.9 vs 10.1, p = 0.001) and platelet counts (235.2 vs 155.1, p = 0.003), and worse Acute Physiology and Chronic Health Evaluation (APACHE) score (4.1 vs 10.2, p < 0.0001) at the time of initial presentation. Technical success was achieved in all 40 cases in which targeted embolization was attempted (100%). Empiric embolization was performed in 6/46 (13.0%) patients based on computed tomographic angiogram (CTA) and operative findings. Stent-grafts were placed in 3 patients for subclavian artery injuries. Availability of pre-intervention CTA was associated with shorter fluoroscopy time (19.8 ± 12.1 vs 30.7 ± 18.6 min, p = 0.030). A total of 41 patients were discharged in stable condition (89.1%). Hollow organ injury was associated with mortality (p = 0.039).

CONCLUSION

Endovascular embolization and stenting were effective in managing hemorrhage due to GSW in a carefully selected population. Hollow organ injury was a statistically significant predictor of mortality. Pre-intervention CTA enabled targeted, shorter and equally effective procedures.

A Review of Professional Liability in IR: Sweeping the Mines

Medical professional liability (MPL) is becoming a substantial issue in interventional radiology (IR), with both impact on health care costs and negative psychological effects on physicians. MPL presents special challenges within IR because of the field's complex and innovative therapies that are provided to a diverse group of patients and complicated by the off-label use of devices and drugs that is pervasive in the field. This review discusses the principles and practices to avoid and manage MPLs that are specific to the field of IR.

Comparing Outcomes in Transcatheter Embolization for the Management of Penetrating versus Blunt Trauma

Purpose This article assesses potential factors associated with successful embolization and/or mortality benefit among patients with penetrating (PT) compared to those with blunt abdominal trauma (BT) undergoing emergent angiography.

Methods A retrospective study of arterial embolization for BT and PT at a tertiary care academic center in an urban setting between 2018 and 2020 was conducted. Fischer's exact and Student's t-tests were used to assess differences between PT and BT, regarding technical success, in-hospital mortality, number of vessels embolized, and requirement of Operating Room (OR) for bleeding control after embolization.

Results Forty-three patients underwent embolization. Twenty-three presented with BT versus 20 with PT. There was no difference in the rate of success between the two groups (91.3% vs. 100%; p = 0.49). No difference was observed in mean days of survival among BT and PT patients treated by embolization (mean [standard deviation]: 13.7 [2.6] vs. 19.1 [2.79] days; p = 0.160). There was no difference in mortality between the two groups (13.0% vs. 10.5%; p = 1.00). Mean number of vessels embolized was higher in the BT group compared to PT (2.26 [1.32] vs. 1.44 [1.03], p = 0.044). The rate of BT patients who required subsequent OR intervention for hemorrhage control after embolization was similar to those with PT (8.7% vs. 10.5%; p = 0.84).

Conclusion The rate of mortality, technical success, and requirement of subsequent OR intervention for hemorrhage control was comparable between BT and PT. BT was associated with a higher mean number of vessels embolized compared to PT. Our case series may provide insight in the use of embolization for PT, but further investigation is needed with larger cohorts.

Recurrent IPDA Aneurysm from Celiac Occlusion Treated by a Flow Diverting Stent

Inferior pancreaticoduodenal artery (IPDA) aneurysms have been associated with celiac axis stenosis and occlusion. Retrograde flow through the IPDA arcade has been hypothesized to cause enlargement of these vessels and lead to aneurysm formation. However, objective proof of this hypothesis is lacking, given the fact that celiac stenosis or occlusion and IPDA aneurysms are typically diagnosed concurrently and recurrent aneurysms have not been described. This report presents a patient with celiac axis stenosis and an IPDA aneurysm treated with median arcuate ligament lysis, celiac stenting, and aneurysmectomy. Seventeen years later, he developed a second IPDA aneurysm treated with a flow diverting stent.

Outcomes of bellwether cases related to inferior vena cava filters in multidistrict litigations

OBJECTIVE

In the present study, we identified and reviewed the outcomes of bellwether cases related to inferior vena cava (IVC) filter multidistrict litigations (MDLs).

METHODS

The legal research database, LexisNexis (New York, NY), was used to identify all cases related to IVC filters. Cases unrelated to the MDLs were excluded. Court documents recording the proceedings for bellwether cases sent to jury trials were retrieved from the LexisNexis subsidiary, Law360. Data on plaintiffs, filter models, reported complications, filed claims, decision-making body, verdicts, and rewards were reviewed.

RESULTS

A total of 678 cases pertaining to IVC filters were found in the database, of which 12 were identified as bellwether cases for MDL. Of the 12, 2 (16.7%) were initially ruled in favor of the plaintiffs in jury trials, although the judgment for 1 of these was later vacated by a judge. The remaining 10 (83.3%) had been decided in favor of the manufacturers by judges and juries.

CONCLUSIONS

Verdicts in all bench trials were in favor of manufacturers, suggesting that judges perceived the presented complications by patients to be within the normal realm of the expected risk of IVC filter use. The findings from the present study have emphasized the treating physicians' legal responsibility to adequately warn patients of all the associated risks with IVC filters. The findings have also indicated that physicians can still be found liable in product liability cases directed at manufacturers. Physicians should continue to actively monitor patients to optimize the IVC retrieval windows.

Inferior Vena Cava Filter Litigation Review: An Analysis of Medicolegal Cases Pertaining to Inferior Vena Cava Filters

PURPOSE

To identify and analyze all medical malpractice and product liability lawsuits pertaining to inferior vena cava (IVC) filters published within a well-recognized legal research database.

MATERIALS AND METHODS

LexisNexis, a legal research database, was used to retrieve cases that mentioned harm from IVC filters, or lack thereof, as the cause for legal action. A total of 672 cases were analyzed for type of case (medical malpractice or product liability), filter model implanted, filter complications, court decisions, and settlement payments if any.

RESULTS

Of 95 analyzed cases, 20 (21.1%) were medical malpractice cases and 75 (78.9%) were product liability cases. C.R. Bard was the manufacturer associated with the most lawsuits (n = 41, 48.8%). The most litigious filters were the G2 filter from C.R. Bard (n = 17, 20.2%) and Greenfield filter from Boston Scientific (n = 17). The most common complications were IVC penetration (n = 26, 29.9%), filter migration (n = 26, 29.9%), filter fracture (n = 23, 26.4%), and tilt (n = 16, 18.4%). The number of product liability cases has increased from accounting for 25.0% (2 of 8) of filter lawsuits between 2000 and 2010 to 83.9% (73 of 87) during 2011-2020. Of the 20 medical malpractice claims, 9 (45%) were filed for failure to place a filter. One physician was found liable for filter-related complications by a state court in 2014.

CONCLUSIONS

The majority of recent IVC filter-related lawsuits are filed against manufacturers on the basis of product liability claims, with the main litigious filters being the G2 and Greenfield filters. Most cases resulted in rulings for physicians or manufacturers. Some were filed against physicians for filter-related complications or for failure to place an IVC filter.

Real-time arteriography-directed percutaneous microwave ablation for small or poorly characterized hepatic lesions using hybrid Angio-CT

PURPOSE

To report the utility of real-time arteriography-directed percutaneous MWA (rad-pMWA) in a hybrid angiography-computed tomography (Angio-CT) suite to treat small or inconspicuous hepatic tumors on non-contrast CT.

METHOD

This single-center retrospective cohort included 15 consecutive patients who underwent rad-pMWA (6 HCC, 4 mCRC, 4 NET, and 1 cholangiocarcinoma). The median longest axial diameter of treated tumors was 1.7 (range: 1.4-6.0) cm. Technical success, contrast use, procedure-related complication, and initial treatment response were recorded.

RESULTS

Technical success was achieved in 15/15 (100%) as shown by no residual enhancement on catheter-directed CT-angiography at the conclusion of the procedure. Average contrast volume use was 63.1 (SD: 29.1) ml. No major arterial access-related complication or residual tumor was noted. Complete ablation rate was 14/14 (100%) at initial 6-8-week follow-up. Local disease progression occurred in one patient during follow-up.

CONCLUSION

Rad-pMWA using Angio-CT is safe and effective for improving tumor visibility and operator convenience. Tumors can be localized with low contrast dosage and ablated with high efficacy with immediate real-time evaluation of the ablation cavity.

Concomitant Lower-Extremity Deep Vein Thrombosis in Patients With Pulmonary Embolism Undergoing Catheter-Directed Therapy

Deep vein thrombosis (DVT) is often seen in patients with acute pulmonary embolism (PE). Risk stratification of PE patients is useful in predicting mortality risk and hospital course. However, rates or predictors of DVT or proximal DVT (popliteal, femoral, common femoral, or iliac thrombosis) have not been studied in the highest-risk patients who receive catheter-directed therapy (CDT) for their PE. A single-center retrospective analysis of patients referred for CDT for confirmed PE was conducted to evaluate rates and predictors of DVT or proximal DVT and the impact on short-term outcomes. In 137 consecutive patients undergoing CDT for PE with available lower-extremity ultrasound, the rates of DVT and proximal DVT in PE patients receiving CDT were 76.6% and 65.0%, respectively. Rates of DVT (P=.68) and proximal DVT (P=.72) did not differ between high-risk or non-high risk PE patients. The only significant factor associated with presence of concomitant DVT was previous DVT (P=.045). The presence of a concomitant DVT or proximal DVT was not associated with an increase in all-cause mortality or hospitalization at 30 days or 1 year compared with an absence of concomitant DVT or proximal DVT. The results of this study suggest that patients with PE clinically requiring CDT have high rates of concomitant DVT and proximal DVT, prior DVT predicts concomitant DVT, and the presence of DVT is not associated with additional risk in this already high-risk population of patients.

Assessment of complication rates based on time of feeding initiation in radiologically guided gastrostomy tubes: a retrospective study

PURPOSE

We aimed to assess the association between complication rate and time to feeding in a cohort of patients undergoing radiologically guided placement of gastrostomy tubes.

METHODS

A retrospective study was conducted of all patients receiving pull-type and push-type gastrostomy tubes placed by interventional radiologists between January 1st, 2017 and December 31st, 2018 at a single institution. Primary outcomes included procedural and tube-related complications per medical chart review with a follow-up interval of 30 days. Exclusion criteria were enteral nutrition delayed more than 48 hours, no feeding information, and tubes placed for venting (n=20). Overall, 303 gastrostomy tubes (pull-type, n=184; push-type, n=119) were included. The most common indications for placement included head and neck carcinoma for push-type tubes (n=76, 63.9%) and cerebral vascular accident for pull-type tubes (n=78, 42.4%).

RESULTS

In a multiple regression analysis, there was no statistically significant association between complications and time to feeding (p = 0.096), age (p = 0.758), gender (p = 0.127), indication for tube placement (p = 0.206), or type of tube placed (p = 0.437). Average time to initiation of enteral nutrition was 12.3 hours for the pull-type and 21.7 hours for the push-type cohort (p < 0.001). Additional multiple regression analyses of pull-type tubes and push-type tubes separately also did not find any significant association between complications and the above factors (p > 0.05).

CONCLUSION

There was no statistically significant correlation between time to feed and complications, suggesting that there is no clinical difference between early and late feeding following gastrostomy tube placement.

Radiation Dose during Transarterial Radioembolization: A Dosimetric Comparison of Cone-Beam CT and Angio-CT Technologies

PURPOSE

To evaluate the radiation dose differences for intraprocedural computed tomography (CT) imaging between cone-beam CT and angio-CT acquired during transarterial radioembolization (TARE) therapies for hepatocellular carcinoma.

MATERIALS AND METHODS

A retrospective cohort of 22 patients who underwent 23 TARE procedures were selected. Patients were imaged in both cone-beam CT and angio-CT rooms as a part of their conventional treatment plan. Effective dose contributions from individual CT acquisitions as well as the cumulative dose contributions from procedural 3D imaging were evaluated. Angiography dose contributions were omitted. Cone-beam CT images were acquired on a C-arm Philips Allura system. Effective doses were evaluated by coupling previously published conversion factors (effective dose per dose-area product) to patient's dose-area product meter readings after the procedure. Angio-CT images were acquired on a hybrid Canon Infinix-i Aquilion PRIME system. Effective doses from angio-CT scans were estimated using Radimetrics. Comparisons of a single patient's dose differential between the 2 technologies were made.

RESULTS

The mean effective dose from a single CT scan was 6.42 mSv and 5.99 mSv in the cone-beam CT room and the angio-CT room, respectively (P = .3224), despite the greater field of view and average craniocaudal scan coverage in angio-CT. The mean effective dose summed across all CTs in a procedure was 12.89 mSv and 34.35 mSv in the cone-beam CT room and the angio-CT room, respectively (P = .0018).

CONCLUSIONS

The mean effective dose per CT scan is comparable between cone-beam CT and angio-CT when considered in direct comparison for a single patient.

An Unusual Case of Resistant Hypertension Secondary to Fibromuscular Dysplasia

A 28-year-old woman with resistant hypertension was given a diagnosis of fibromuscular dysplasia with 100% occlusion of a right renal artery branch supplying an atrophied lower pole, collateralized by the right adrenal artery. Successful adrenal collateral coil embolization restored normotension, but hypertension recurred, necessitating right partial heminephrectomy with blood pressure normalization off medications. (Level of Difficulty: Intermediate.)

Improved Utilization Following Conversion of a Fluoroscopy Suite to Hybrid CT/Angiography System

PURPOSE

To assess changes in operational utilization following conversion of a single IR suite to a hybrid CT/angiography (Angio-CT) system at an academic tertiary care center.

MATERIALS AND METHODS

The total number of interventional procedures and diagnostic CT examinations performed in 29 rooms (20 diagnostic radiology, 7 IR, 2 shared between divisions) was calculated in the 24 months before conversion of an IR suite to Angio-CT and 12 months after conversion. The total number of IR procedures (global IR/month) and diagnostic CT scans per month (global CT/month) in both before and after conversion periods was calculated and defined as baseline institutional growth. This was compared against the change in the number of IR procedures performed in the before and after periods in the converted room (Angio-CT/month) as well as the number of diagnostic CT scans performed in the shared rooms (shared CT/month).

RESULTS

The percent change in global CT and global IR from the before to the after periods was 39.2% and 3.1%, respectively. Shared CT per month and Angio-CT per month increased by 46.7% and 12.0% across the same time periods, respectively. The ratio of the percent increase in Angio-CT per month to percent increase in global IR per month was 3.87. The ratio of the percent increase in shared CT per month to percent increase in global CT per month was 1.19.

CONCLUSIONS

Operational utilization improved in both diagnostic radiology and IR sections following conversion of a conventional fluoroscopic IR suite to an Angio-CT room.

A cohort study showing correspondence of low wall shear stress and cephalic arch stenosis in brachiocephalic arteriovenous fistula access

BACKGROUND

A brachiocephalic fistula is frequently placed for hemodialysis; unfortunately, cephalic arch stenosis commonly develops, leading to failure. We hypothesized that a contribution to brachiocephalic fistula failure is low wall shear stress resulting in neointimal hyperplasia leading to venous stenosis. The objective of this investigation is to determine correspondence of low wall shear stress and the development of cephalic arch stenosis.

METHODS

Forty subjects receiving hemodialysis with a primary brachiocephalic fistula access were followed from time of placement for 3 years or until cephalic arch stenosis. Venogram, Doppler, and viscosity were performed at time of fistula maturation, annually for 3 years or to time of cephalic arch stenosis. Computational hemodynamics modeling was performed to determine location and percent low wall shear stress in the arch. The relationship between wall shear stress at time of maturation and location of cephalic arch stenosis were estimated by correlating computational modeling and quadrant location of cephalic arch stenosis.

RESULTS

In total, 32 subjects developed cephalic arch stenosis with 26 displaying correspondence between location of low wall shear stress at time of maturation and subsequent cephalic arch stenosis, whereas 6 subjects did not (p = 0.0015). Most subjects with correspondence had low wall shear stress areas evident in greater than 20% of the arch (p = 0.0006). Low wall shear stress was associated with a higher risk of cephalic arch stenosis in the 23-to-45 age group (p = 0.0029).

CONCLUSIONS

The presence and magnitude of low wall shear stress in the cephalic arch is a factor associated with development of cephalic arch stenosis in patients with brachiocephalic fistula. Attenuation of low wall shear stress at time of maturation may help prevent the development of cephalic arch stenosis which is difficult to treat once it develops.

Thoracic Duct Embolization Using Direct Hybrid Angiography/Computed Tomography‑Guided Cisterna Chyli Access for the Treatment of Chylous Leak Secondary to Partial Glossectomy and Neck Dissection

Thoracic duct embolization (TDE) is a minimally invasive alternative to surgery for the treatment of postoperative chylous leaks that fail conventional medical management. TDE can be a technically challenging procedure that requires real-time image guidance to visualize the thoracic duct. This case report describes using hybrid angiography/computed tomography technology to perform TDE through direct access of the cisterna chyli, potentially eliminating the need for intranodal lymphangiography, and reducing procedure length.

Gastrointestinal Bleeding on Call: Questions and Answers and One Person's Opinions

Gastrointestinal (GI) bleeding represents one of the more morbid forms of hemorrhage that interventional radiologists deal with on an on-call basis. Bleeding from the GI tract takes many forms and has many etiologies. While venous bleeds from varices are often treated emergently with placement of a transjugular intrahepatic portosystemic shunt, arterial hemorrhages are treated most effectively with embolization procedures. Embolization must be performed in specific ways, however, in an effort to decrease the risk of bowel ischemia; this also requires choosing the right patients in whom to perform embolization procedures. This article will provide a discussion on when to perform embolization and how, what to do with specific patient populations such as those with coagulopathy, and which patients should be considered for emergent treatment versus those that can be postponed.

Inferior Vena Cava Filter Evaluation and Management for the Diagnostic Radiologist: A Comprehensive Review Including Inferior Vena Cava Filter-Related Complications and PRESERVE Trial Filters

Inferior vena cava filters are commonly encountered devices on diagnostic imaging that were highlighted in a 2010 Food and Drug Administration safety advisory regarding their complications from long-term implantation. The Predicting the Safety and Effectiveness of Inferior Vena Cava Filters (PRESERVE) trial is an ongoing after-market study investigating the safety and utility of commonly utilized filters in practice today. While most of these filters are safe, prompt recognition and management of any filter-associated complication is imperative to prevent or reduce the morbidity and mortality associated with them. This review is aimed at discussing the appropriate utilization and placement of inferior vena cava filters in addition to the recognition of filter-associated complications on cross-sectional imaging. An overview of the PRESRVE trial filters is also provided to understand each filter's propensity for specific complications.

A Single-Institutional Comparative Analysis of Advanced Versus Standard Snare Removal of Inferior Vena Cava Filters

PURPOSE

To investigate differences in procedure time, radiation exposure, and periprocedural complications associated with advanced inferior vena cava (IVC) filter retrieval compared with standard snare retrieval.

MATERIALS AND METHODS

A total of 378 patients underwent standard or advanced IVC filter retrieval over a 5-year period. Technical success, retrieval techniques, fluoroscopy time, radiation dose, and complications were analyzed. All retrieval procedures with techniques other than a "snare-and-sheath" method were categorized as advanced, including failed standard attempts requiring intraprocedural conversion to advanced techniques.

RESULTS

A total of 462 filter retrieval attempts were made in 378 patients (57% female). Success rates for standard and advanced retrieval attempts were 86.8% (317 of 365) and 91.8% (89 of 97), respectively. The rate of periprocedural complications was significantly higher in the advanced retrieval group (P = .006). Complication rates for standard and advanced retrievals were 0.6% (2 of 318; all minor) and 5.2% (5 of 97; 3 minor [3.1%] and 2 major [2.1%]), respectively. The 2 major complications during advanced retrievals included filter fracture and embolization. Average fluoroscopy time for advanced retrievals was significantly higher than for standard retrievals (23.1 min vs 4.3 min; P < .001). Average radiation dose for advanced retrievals was also significantly higher than for standard retrievals (557.2 mGy vs 156.9 mGy; P < .001). Use of general anesthesia was also significantly more common in advanced retrievals compared with standard retrievals (6.2% vs 0.9%; P = .002).

CONCLUSIONS

Advanced filter retrieval results in a similarly high rate of technical success compared with standard snare retrieval but is associated with greater fluoroscopy time, anesthesia requirements, and radiation exposure.

Inferior Vena Cava Filters: Why, Who, and for How Long?

Vena cava filters are implantable devices that are placed to trap thrombus originating in the lower extremities and prevent it from migrating to the lungs. In general, inferior vena cava (IVC) filters are indicated for patients who cannot receive anticoagulation. Other indications for IVC filtration are less clear, and guidelines vary. All patients who have a retrievable IVC filter should be followed, and the removal of the IVC filter should be considered once its indication is lost.

Increased Inlet Blood Flow Velocity Predicts Low Wall Shear Stress in the Cephalic Arch of Patients with Brachiocephalic Fistula Access

Background

An autogenous arteriovenous fistula is the optimal vascular access for hemodialysis. In the case of brachiocephalic fistula, cephalic arch stenosis commonly develops leading to access failure. We have hypothesized that a contribution to fistula failure is low wall shear stress resulting from post-fistula creation hemodynamic changes that occur in the cephalic arch.

Methods

Twenty-two subjects with advanced renal failure had brachiocephalic fistulae placed. The following procedures were performed at mapping (pre-operative) and at fistula maturation (8–32 weeks post-operative): venogram, Doppler to measure venous blood flow velocity, and whole blood viscosity. Geometric and computational modeling was performed to determine wall shear stress and other geometric parameters. The relationship between hemodynamic parameters and clinical findings was examined using univariate analysis and linear regression.

Results

The percent low wall shear stress was linearly related to the increase in blood flow velocity (p < 0.01). This relationship was more significant in non-diabetic patients (p < 0.01) than diabetic patients. The change in global measures of arch curvature and asymmetry also evolve with time to maturation (p < 0.05).

Conclusions

The curvature and hemodynamic changes during fistula maturation increase the percentage of low wall shear stress regions within the cephalic arch. Low wall shear stress may contribute to subsequent neointimal hyperplasia and resultant cephalic arch stenosis. If this hypothesis remains tenable with further studies, ways of protecting the arch through control of blood flow velocity may need to be developed.