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Monday, October 24, 2016

Covered stents vs. PTA for ISR in AVGs and AVFs: Results from the RESCUE study

Despite the prevalence and morbidity conveyed by in-stent restenosis following bare-metal stent placement in hemodialysis access circuits, there has been limited evidence to guide optimal therapy. The RESCUE Study was the first prospective multicenter randomized, concurrently-controlled clinical trial designed to compare the efficacy and safety of expanded polytetrafluoroethylene (ePTFE) stent-grafts following balloon pre-dilation (n=132) versus percutaneous transluminal angioplasty (PTA) alone (n=143) for the treatment of venous outflow in-stent stenosis. Primary outcomes were access circuit primary patency (ACPP) at 6 months and freedom from complications through 30 days. The stent-graft group demonstrated significantly higher ACCP at 6 months, of 18.6% compared to 4.5% in the PTA group (p<0.001), an effect which was maintained to 12 months (6.2% vs. 1.5% respectively). These differences persisted when stratifying by access type (grafts versus fistulae) or stenosis location (peripheral versus central veins). A secondary outcome, treatment area primary patency (TAPP) at 6 months, was also significantly higher in the stent-graft (66.4%) versus PTA (12.3%) groups (p<0.001). There was no significant difference in the rate of safety events between treatment groups at 30 days (p<0.003) or through the full 24-month follow-up period. The investigators concluded that stent grafts provide superior primary patency than PTA alone for in-stent stenosis in AV grafts or native fistulae, for both peripheral and central veins, while maintaining a non-inferior safety profile to PTA.


The RESCUE study serves as a well-designed and powered, comprehensive evaluation on the use of stent-grafts versus PTA alone to address in-stent restenosis for dialysis access circuits, an area which was previously under-investigated. The improved patency outcomes and absence of more frequent adverse events for stent-grafts compared to PTA in both fistulae and grafts provide strong support for their broader application in the setting of in-stent restenosis, and echoes favorable stent-graft outcomes seen in other locations in dialysis access circuits (i.e. venous anastomosis in RENOVA study). The cost efficacy of stent-grafts was not addressed in this study, but is an issue which necessitates future investigation, particularly when considering that the long-term ACCP rates remained very low (0.9% for stent-graft versus 0.8% for PTA at 24 months), despite concurrent improvements in TAPP. Nonetheless, the RESCUE study provides much needed evidence toward elucidating the optimal role of stent-grafts in dialysis access circuit preservation.

Click here for full text

Falk A, Maya ID, Yevzlin AS, Investigators R. A Prospective, Randomized Study of an Expanded Polytetrafluoroethylene Stent Graft versus Balloon Angioplasty for In-Stent Restenosis in Arteriovenous Grafts and Fistulae: Two-Year Results of the RESCUE Study. J Vasc Interv Radiol 2016; 27:1465-76.

Post Authors:

Jeffrey Forris Beecham Chick, MD, MPH
University of Michigan Hospital System

James X. Chen, MD
Hospital of the University of Pennsylvania

Monday, October 17, 2016

The Manuscripts We Deserve.

“He's the hero Gotham deserves, but not the one it needs right now. So we'll hunt him. Because he can take it. Because he's not our hero. He's a silent guardian, a watchful protector. A dark knight.”

- Jim Gordon

Too often I have read a paper or watched a lecture and thought, “That is compelling evidence, I should definitely start doing that.” However, I always fall back on tried and true methods because, “that’s the way I’ve always done it” or “it’s always worked for me.” Take a look at the papers presented below. These manuscripts have data that can help define your daily practice. Will they define it in a profound manner and be a milestone by which you judge your career? Maybe not. However, these are the papers that we as a specialty should be taking note of. Real data with definable action items that you can implement into your daily grind. We need papers that question if that annoying CVC-tip thrombus is really clinically significant or evaluate if the indirect portal venogram (aka arterial portography) is really necessary in the 21st century. While our specialty can change and adapt at acute angles, we will more likely adjust our course through small, definable change. The authors that presented these manuscripts should be applauded. They are the offensive linemen of our specialty. Slogging through it not for some flash in the pan new way to treat HCC, but for changing our daily flow. We need the dreamers but we also need people putting in the gritty work to answer those annoying questions that everyone else doesn’t have the patience for.

What to do with the annoying catheter-tip associated thrombus detected on echo?

Chick JF, Reddy SN, Bhatt RD, Shin BJ, Kirkpatrick JN, Trerotola SO. Significance of echocardiographically detected central venous catheter tip-associated thrombi. J Vasc Interv Radiol. 2016. doi: 10.1016/j.jvir.2016.07.013

Click here for abstract

The authors evaluated 170 echocardiograms and found 49 patients with CVC tip-associated thrombi. Ejection fraction, presence of a PFO, other intracardiac shunt, and mean thrombus size were all evaluated. A variety of outcome measures were collected including management decision, thrombus, extension, PE, paradoxical emboli, and stroke within 3 months. Of the 49 patients with CVC tip–associated thrombi, those without PFO or other intracardiac shunts had no embolic or other complications detected, regardless of anticoagulation status. The authors conclude that, “This suggests a benign course for such thrombi and that anticoagulation, catheter removal, thrombectomy, and thrombolysis may be unnecessary when catheter tip–associated thrombi are incidentally detected on echocardiography.”

Do we really need the post-retrieval IVC-gram?

Mintz JD, Stavropoulos SW, Trerotola SO. Is a venacavogram necessary after inferior vena cava filter retrieval? J Vasc Interv Radiol. 2016. doi: 10.1016/j.jvir.2015.08.016

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Authors looked at the utility of IVC-gram after 224 IVC filter retrievals using routine and complex techniques. Complex retrievals included forceps or other adjuncts. The IVC-gram from the retrievals was evaluated for stenosis, filling defect, dissection, and extravasation. Abnormalities requiring additional treatment were considered major and those that required no additional treatment were considered minor. Minor abnormalities were seen in 52% of routine retrievals and 79% of complex retrievals. The results were significant with a P<0.01. Major abnormalities were seen in 3% of complex retrievals and 0% or routine retrievals. The authors conclude that the lack of major abnormalities on venacavography after routine IVC filter retrieval “may justify omitting venacavography after retrieval regardless of dwell time.” However, extravasation can be infrequently seen after complex retrieval and will require additional treatment. Therefore, “venacavography remains warranted in this setting.”

Do we still need to do an indirect portal venogram prior to TACE?

Hui TC, Pua U. Arterial portography during transarterial chemoembolization: still a necessity in the age of contrast-enhanced cross-sectional imaging? J Vasc Interv Radiol. 2014. 25:41-46.

Click here for abstract

This manuscript evaluates the necessity of arterial portography (AP) if a patent PV is seen on cross-sectional imaging prior to TACE. This study included 243 total procedures with 93 of those undergoing an AP. The mean time between imaging and TACE was 46.5 days. No new cases of portal vein thrombosis were detected on AP when pre-procedure imaging demonstrated a patent portal vein. However in the group that omitted AP, post-prcoedure imaging showed one case of main PVT, 2 right PVT, and 2 left PVT. No significant difference in morbidity or mortality were detected between the two groups. The authors conclude that “AP is unnecessary if TACE is performed in a reasonable time frame” following CT or MRI demonstrating a patent PV.

Post author:
Luke R. Wilkins, MD
University of Virginia

Friday, October 14, 2016


Teaching Topic: Yttrium-90 Radioembolization as Salvage Treatment following Chemoembolization for Hepatocellular Carcinoma

Johnson G, Monsky L, Valji K, Hippe D, Padia S. Yttrium-90 Radioembolization as Salvage Treatment following Chemoembolization for Hepatocellular Carcinoma. J Vasc Interv Radiol. 2016. 27 (8): 1123-9.

Click here for abstract

A recent article in JVIR retrospectively evaluated the safety and efficacy of Yttrium-90 (90Y) transarterial radioembolization in patients who have undergone TACE for HCC at a single institution. 40 patients with multifocal disease were identified that had undergone a Tc-99m mapping study. The patients had a median age of 61 years, with various tumor stages and classes, with a median tumor diameter of 4.2 cm (range 1-11.6 cm). There were 28 (70%) Child-Pugh class A patients and 12 (30%) class B. 106 prior TACE procedures were performed on this group of patients, using drug eluting embolic agents and oiled based agents; 29 underwent TARE, with 11 excluded after their mapping study indicated that Y90 would be contraindicated. Follow up imaging was done 1 month and 3 months there-after, with tumor response assessed by tumor size. Most common grade ≥ 3 toxicities were fatigue and biochemical alterations. Of 27 patients treated with TARE with follow-up, 60% had partial or complete response and only 33% had progression of disease. Median progression-free survival and overall survival were 90 days and 257 days. Median follow-up was 266 days. The authors conclude that TARE may be considered for salvage therapy in patients after TACE with a median overall survival comparable to other large series using TARE for HCC.

Clinical Pearls

What were some limiting factors and important timelines to mention regarding this study?

Salvage therapy via TACE may be limited by tumor progression, portal vein invasion, and technical inability to deliver a chemoembolic agent secondary to arterial changes resulting from prior chemoembolization, poor patient tolerance, or progression of underlying liver disease. In the event of exhaustion of chemoembolization options, TARE could be considered as a salvage treatment.

After TACE, hepatic arterial recanalization is known to occur overtime, although variable due to which chemoembolic agent was used during TACE. This study suggests that patients who were mapped less than 90 days and over 365 days from the most recent TACE were more feasible for TARE than those who fell in the time between.

Other limitations included a small sample of patients not having adequate hepatic arterial blood flow due to attenuation in patency, as a result >4 TACE procedures in the past. These patients did not undergo TARE. (Please see below Figure A)

Figure A: Mapping hepatic arteriogram in a 61-year-old man with HCC and a history of multiple hepatic chemoembolization procedures. Vague tumor hypervascularity (arrow) is seen in the superior aspect of the right lobe. There is marked attenuation of the distal hepatic arteries. The patient was deemed not to be a candidate for radioembolization because of the condition of the hepatic 

Further, retrospective investigation on its own is a limitation that may be clinically significant. The TARE procedure technique was consistent, however, the differences in TACE technique may mount to changes in the results, given their effects on arterial vasculature in some patients. This heterogeneity remains a major obstacle in all chemoembolization studies. Also, after mapping, the decision to proceed to TARE was left up to the Interventional Radiologist.

Questions to Consider

Besides post TACE salvage therapy for HCC with 90Y, what has TARE commonly been used to treat?

Palliative treatment of non-resectable metastatic disease to the liver, usually colorectal has become popular using 90Y-labeled glass or resin microspheres (TheraSphere and SIR-Sphere) in the last several years. The benefits of this technique include more precise targeting of tumor volumes, decreases side effects and morbidity, and decreased radiation of normal tissues. Microsphere sizes vary from 20 to 60 microns in diameter and is delivered via an angiographic catheter into the hepatic artery. Treatment activity localizes in the capillary bed of the hypervascular tumor and, to a lesser extent, in the normal parenchyma. Radiation dose diameter is about 2.4mm, with a typical activity of about 40-70mCi. 

What are patient assessment measures to be taken prior and following to 90Y treatment?

Patient assessment includes issues related to tumor resectibility, disease extent, extrahepatic involvement, hepatic vascular anatomy, AV shunting, liver and kidney function and the general health of the patient.

Imaging workup begins with angiographic evaluation of abdominal aorta, celiac access, SMA and hepatic arteriograms to identify anatomy, followed by embolization of the Gastroduodenal artery and sometimes, the Right Gastric Artery.

Before 90Y microsphere delivery, during the mapping portion of the procedure, catheter directed 99mTc macroaggregated albumin infusion into the hepatic artery followed by nuclear medicine imaging is performed to rule out hepatopulmonary shunting (>20%), which could cause radiation pneumonitis. Other possible shunts include those to the stomach, gallbladder and the duodenum.

Patients may head back home after the procedures without any special instructions for linens and clothing, but a small amount of activity could be present in the urine. As a result, for the first immediate 24 hours, a toilet should be used and flushed twice. Patient should have short term follow up imaging (usually 3 months) after treatment. 

Additional reading:

Gaba RC. Plannng arteriography for yttrium-90 microsphere radioembolization. Semin Intervent Radiol 2015; 32: 428-438.

Click here for full text

Lewandowski RJ, Salem R. Yttrium-90 radioembolization of hepatocellular carcinoma and metastatic disease of the liver. Semin Intervent Radiol 2006; 23: 64-72.

Click here for full text

Post author:
Ali Alikhani, MD
Diagnostic Radiology Resident, PGY-4
University of Tennessee Methodist Healthcare

Thursday, October 6, 2016

From the SIR Residents and Fellows Section (RFS)

Teaching Topic: Inferior Vena Cava Filters in Pregnancy: A Systematic Review

Harris SA, Velineni R, Davies AH. Inferior vena cava filters in pregnancy: a systematic review. J Vasc Interv Radiol. 2016. 27(3):354-60.

Click here for abstract

Pregnancy can cause patients to be at increased risk for venous thromboembolism and is an important cause of maternal mortality. This systematic review sought to collate the available information on the use of IVC filters in pregnancy. A total of 44 articles with 124 total pregnancies were able to be identified. The articles were case reports or case series without any randomized controlled trials. The authors argue there is currently not enough evidence to suggest that IVC filters should be routinely used in pregnancy in patients with DVT. While the use of retrievable filters is attractive in this young, healthy patient population, until further studies are carried out, their use should be considered for the same absolute indications as in the nonpregnant population or in individuals in whom there are concerns surrounding delivery. The manuscript reports complication rates that are comparable to those in the nonpregnant population. In addition, while suprarenal and infrarenal positioning can be used, there are more theoretical benefits to suprarenal placement. The authors conclude that IVC filters can be used safely, when appropriate, during pregnancy. However, as always, long-term follow-up data is lacking and further research is warranted.

Clinical Pearls

What is the rate of VTE in pregnancy?

The author quotes rates of VTE in pregnancy as 0.79 in 100,000 maternities and the 3rd most common cause of maternal mortality in Great Britain, specifically. Worldwide incidence of VTE has been quoted up to 3.24 per 1000 women years accounting for 15% of maternal mortality.

What is the proposed mechanism of the increased risk of VTE?

The rate of VTE is 5 times higher during pregnancy and 60 times higher in the postpartum period. The etiology is theorized to be secondary to adaptions in the hemostatic system in preparation for the hemostatic challenge of delivery in combination with the venous stasis that occurs with a gravid uterus and increased plasma volume. Furthermore, there may be vascular endothelial damage that occurs from distention or surgical intervention, which promote thrombus formation.

What is the standard treatment in pregnancy?

Medical management is the first line treatment for VTE in pregnancy. Patients are treated with low molecular weight heparin throughout the pregnancy up until at least 6 weeks postpartum. Warfarin is avoided due to its ability to cross the placenta.

Questions to Consider

What are the Society of Interventional Radiology Guidelines (SIR) regarding the absolute indications, relative indications, and contraindications for IVC filter placement?

Absolute Indications (Proven VTE)
- Recurrent VTE (acute or chronic) despite adequate anticoagulation
- Contraindication to anticoagulation
- Complication of anticoagulation
- Inability to achieve/maintain therapeutic anticoagulation

Relative Indications (Proven VTE)
- Iliocaval DVT
- Large, free-floating proximal DVT
- Difficulty establishing therapeutic anticoagulation
- Massive PE treated with thrombolysis/thrombectomy
- Chronic PE treated with thromboendarterectomy
- Thrombolysis for iliocaval DVT VTE with limited cardiopulmonary reserve
- Recurrent PE with filter in place
- Poor compliance with anticoagulant medications
- High risk of complication of anticoagulation (eg, ataxia, frequent falls)
- Prophylactic Indications (No VTE, primary prophylaxis not feasible)
- Trauma patient with high risk of VTE
- Surgical procedure in patient at high risk of VTE
- Medical condition with high risk of VTE

Contraindications to Filter Placement
- No access route to the vena cava
- No location available in vena cava for placement of filter

What considerations are especially relevant regarding IVC filter placement in pregnancy?

An additional consideration in pregnancy is that anticoagulation is stopped during both vaginal and caesarian delivery, increasing the risk of VTE in this time period. Therefore, a filter may be placed prior to delivery. This relative indication is addressed by the above SIR guideline, “medical condition with high risk of VTE” and/or “difficulty maintaining therapeutic anticoagulation”.

SIR consensus guidelines state that some patients with indications for vena cava filters have limited periods of risk of clinically significant PE and/or contraindication to anticoagulation and may not require permanent protection from PE with a vena cava filter. This tenant applies to most pregnant patients and therefore removable filters are preferred. According to this study, rates of non-retrieval in the pregnant population (11.25%) is comparable to the non-pregnant population (12.1%).

What are the theoretical benefits to suprarenal IVC filter placement in pregnancy?

It is thought that below the level of the renal veins, it is more likely that the IVC filter can be crushed/fractured due to compression from a gravid uterus which may lead to migration of the filter and damage to the IVC wall. Suprarenal placement may also provide additional protection from thrombus which may have developed in the ovarian veins. Finally, the increased venous flow from the renal veins may promote clot lysis of trapped thrombi.

Additional citations:
Pomp ER, Lenselink AM, Rosendaal FR, Doggen CJ. Pregnancy, the postpartum period and prothrombotic defects: risk of venous thrombosis in the MEGA study. J Thromb Haemost. 2008 Apr. 6(4):632-7.

Kaufman JA, Kinney TB, Streiff MB, Sing RF, Proctor MC, Becker D, Cipolle M, Comerota AJ, Millward SF, Rogers FB, Sacks D, Venbrux AC. Guidelines for the use of retrievable and convertible vena cava filters: report from the Society of Interventional Radiology multidisciplinary consensus conference. J Vasc Interv Radiol. 2006 Mar;17(3):449-59.

Post author:
Lindsay Karr Thornton, MD
Diagnostic Radiology Resident, PGY-4
University of Florida

Friday, September 30, 2016

From the SIR Residents and Fellows Section (RFS)

Teaching Topic: The Use of Denver Shunts to Manage Chylous Ascites.

Yarmohammadi H, Brody LA, Erinjeri JP, et al. Therapeutic Application of Percutaneous Peritoneovenous (Denver) Shunt in Treating Chylous Ascites in Cancer Patients. J Vasc Interv Radiol 2016; 27: 665-673.

Click here for abstract

This manuscript revaluates the safety and efficacy of percuntaneous and peritoneovenous shunt (PPVS) placement in treating intractable chylous ascite (CA) in patients with cancer. The study from Memorial Sloan-Kettering Cancer Center involved 28 patients with refractory CA. The authors report resolution of ascites or symptom relief in 92% of patients with statistically increased levels of serum albumin in the PPVS placement group. The reported complication rate was 37% with shunt malfunction/occlusion being the most common at 22%. Both smaller venous limb size and presence of peritoneal tumor were associated with higher rates of shunt malfunction.

Clinical Pearls

How does chylous ascites (CA) form?

This study focused on CA (milky appearance of the ascites with an ascitic fluid triglyceride concentration > 110 mg/dL) as a complication of surgical therapy for urologic malignancy, which requires retroperitoneal lymph node dissection (LND). Post-surgical CA can form early, due to damage to the lymphatics themselves, or late, due to adhesions and extrinsic compression on the lymphatic system. Other causes include: malignant compression on lymphatic vessels, cardiovascular disease, such as right heart failure, causing increased lymphatic pressure, hepatic cirrhosis causing disruption of serosal lymphatic channels, infections, such as peritoneal tuberculosis and filariasis, congenital conditions, such as primary lymphatic hypoplasia and Klippel-Trenaunay (lymphatic hypoplastic malformations), or inflammatory conditions such as radiation injury and acute or chronic pancreatitis.

What treatment options are available and how does the Denver shunt work?

Traditionally, CA is managed by conservative diet modification, involving a high-protein, low-fat, medium-chain triglyceride (MCT) oral diet or total parenteral nutrition. Dietary restriction of long-chain triglycerides (LCT) avoids their conversion into monoglycerides and free fatty acids (FFA), which require transport as chylomicrons via intestinal lymph ducts. By contrast, MCTs are absorbed directly into intestinal cells and transported as FFA and glycerol directly to the liver via the portal vein. One of the main problems with conservative management and paracentesis is loss of nutrients and the risk of developing malnutrition. Pharmacological agents, such as somatostatin and octreotide, have been shown to be successful in treating chylous ascites. Paracentesis is performed as needed to palliate symptoms. Peritoneovenous shunt (PVS) placement for treatment of refractory ascites was first described by Smith in 1962. The Denver shunt (CareFusion Corporation, San Diego, California) pump is percutaneous PVS (PPVS) that is either single-valved or double-valved. These shunts redistribute ascitic fluid from the abdomen into the central circulation based on a pressure gradient between the abdomen and central venous system and incorporate a compressible valve chamber between the peritoneal limb and the venous limb to prevent reflux of fluid back into the peritoneal cavity, providing unidirectional flow.

Questions to consider

When should PPVS placement and removal be considered?

Persistent or refractory CA not responding to 2 weeks of conservative treatment and repeated paracentesis was the threshold for PPVS placement in this study. Patients’ high-protein, low-fat diet was switched to a regular diet after the procedure. Patients were instructed to pump the shunt 20 times, twice a day, once in the morning and once before bedtime while in the supine position. Initial symptomatic relief (abdominal distention) was evaluated at the 1-week visit and was achieved in 100% of patients. CA permanently resolved in patients with urologic malignancies, whose ascites had resulted from retroperitoneal LND. In the remaining 15 patients, palliation of symptoms until shunt removal or death was achieved in 13 (87%). Based on the results of the present study, the recommendation is that when a patient experiences changes in pump consistency and there is no clinical or radiographic evidence of ascites, the shunt can be removed.

What complications should be considered for PPVS?

Reported complications of PPVS placement include shunt occlusion, gastrointestinal tract (variceal) bleeding, infection, and DIC. The most common complication in this study was PPVS malfunction/occlusion (21%). Using a large venous limb (15.5F) was noted to occlude less than systems using a 11.5F venous limb. Patients with peritoneal tumors (lymphangioleiomyomatosis [LAM] and peritoneal mesothelioma) should be expected to have repeated occlusions. Two patients (7%) developed asymptomatic or subclinical DIC. One proposed reason for development of DIC is rapid introduction of the ascitic fluid containing high levels of fibrin-rich procoagulants, including endotoxin, thromboplastin activated clotting factors, and plasminogen activator, into the central venous system. In CA, the main reason for ascites formation is leakage of chyle secondary to the obstruction or disruption of the lymphatic system and returning the chylous fluid back into the circulation is actually physiologic. The authors have suggested limiting the risk of DIC by draining the ascites to completion at the time of shunt placement and replacing the ascitic fluid with 4L of normal saline to avoid putting into circulation a large amount of potentially DIC-inducing substances.

Post Author:
Rajat Chand, MD
Diagnostic Radiology Resident, R-1
John H. Stroger Jr. Hospital of Cook County

Thursday, September 22, 2016

From the SIR Residents and Fellows Section (RFS)

Teaching Topic: Position Statement on Noninvasive Imaging of Peripheral Arterial Disease by the Society of Interventional Radiology and the Canadian Interventional Radiology Association

Dhanoa D, Baerlocher MO, Benko AJ, Benenati JF, Kuo MD, Dariushnia SR, Faintuch S, Midia M, Nikolic B. Position statement on noninvasive imaging of peripheral arterial disease by the Society of Interventional Radiology and Canadian Interventional Radiology Association. J Vasc Interv Radiol. 27: 947-51.

This manuscript reviews and provides recommendations for noninvasive lower-extremity imaging of PAD. This includes both functional and anatomic tests. The functional or physiologic tests include the ankle-brachial index (ABI), segmental limb pressures, pulse volume recordings (PVRs), segmental Doppler waveforms, and oxygen testing. The anatomic tests include duplex ultrasound (US), computed tomography (CT), and magnetic resonance (MR) imaging. Because of the complexities and degree of discussion needed for each study, CT and MR imaging will be discussed in a future manuscript. Given changes to our delivery of healthcare in the United States, the manuscript serves an important role in defining the appropriate use of noninvasive imaging to improve patient selection and documenting post-procedure outcomes.

Clinical Pearls

What imaging modalities constitute a complete noninvasive examination of peripheral arterial disease?

A typical noninvasive examination should always include an ABI with concomitant pulse volume recordings (PVRs), continuous-wave Doppler analysis, segmental pressures, and exercise testing.

Why is a position statement on noninvasive imaging of PAD needed?

The implementation of the Affordable Care Act has brought about drastic changes to the reimbursement models for medicine. Alternative methods have emerged to enact the intended paradigm shift towards value-based and outcome-oriented delivery of healthcare instead of the standard, traditional merit-based fee-for-service model. Thus, the appropriate use of noninvasive imaging to improve pre-procedural patient selection, as well as to objectively document post-procedure outcomes, is of critical significance.

Questions to Consider

How are ABIs calculated and how are results utilized to grade PAD?

ABIs are calculated by dividing the ankle systolic blood pressure by the brachial artery systolic blood pressure. Both upper extremity BP are obtained and the higher of the two are utilized. For the ankle systolic BP, the greater of the dorsalis pedis or posterior tibial artery should be used.

If there is a >15mmHg discrepancy between the upper extremity systolic blood pressures, hemodynamically significant disease should be considered to be present proximal to the brachial artery with the lower systolic blood pressure.

Stielger et al. proposed an ABI-Based Grading Scale as follows:
  • >1.3 : Falsely high value (suspicious for medial sclerosis) 
  • 0.9-1.3 : Normal 
  • 0.75-0.9 : Mild PAD 
  • 0.4-0.75 : Moderate PAD 
  • <0.4 : Severe PAD 
What are the important limitations to ABIs?

ABIs can be falsely elevated in patients with heavily calcified arteries. In these circumstances, it is recommended that toe brachial index be utilized as calcifications are rarely found at the great toe. A TBI of >0.65 is considered normal and TBI < 0.4 is considered severe PAD.

What are the four phases of a normal typical waveform in segmental PVR?

The four phases are:

1. A rapid systolic upstroke
2. Rapid diastolic downstroke
3. Prominent dicrotic notch (*The dicrotic notch denotes the closing of the Aortic Valve)
4. Normalization to baseline before the next cycle

How do you interpret arterial Doppler waveforms?

Normal arterial Doppler waveforms are triphasic consisting of a sharp systolic upstroke, reversal of flow below baseline and then a short forward component in late diastole. Mild PAD leads to a bisaphic waveform in which the short forward component in late diastole is lost. As PAD progresses to severe disease, the waveform continues to flatten and becomes monophasic with loss of the flow reversal. The waveform becomes rounded with a slow upstroke and slow downstroke creating the classic postobstructive tardus parvus signal.

Post Author:
Andrew Niekamp, MD
Diagnostic Radiology Resident, PGY-3
UT Houston

Thursday, September 15, 2016

From the SIR Residents and Fellows Section (RFS)

Teaching Topic: Endovascular Repair of Celiac Artery Aneurysm with the use of Stent Grafts

Zhang W, Fu YF, Wei PL, E B, Li DC, Xu J. Endovascular repair of celiac artery aneurysm with the use of stent grafts. J Vasc Interv Radiol. 2016. 27 (4): 514-8.

A recent article in JVIR evaluated the feasibility, safety, and long-term outcome of stent-graft insertion for endovascular repair of celiac artery aneurysms (CAAs). 10 patients with CAAs underwent endovascular repair via stent-graft insertion in a single center. Follow-up CTAs were performed at 1, 3, 6, and 12 months. There was no evidence of endoleak, stent obstruction, or splenic infarction during the follow-up period and all 10 patients had CAA sac shrinkage or increased CAA sac thrombus on follow-up imaging.

Clinical Pearls

What do we know about aneurysms involving visceral arteries?

Visceral arterial aneurysm (VAA) are rare, with an incidence of 0.1%–2%. Celiac artery aneurysms (CAA) constitute 4.8%–6.3% of all VAA cases. In this study, the treated aneurysms varied from 2.1 x 1.6 cm to 8.8 x 7.1 cm. They frequently present as a life-threatening emergency and are often fatal if associated with rupture. An aneurysm ≥ 20 mm in size is considered sufficient to warrant treatment if the patient’s overall condition permits it. Recent studies have reported treatment options for CAAs consisting of open surgery or embolization. Few publications have reported stent-graft insertion for endovascular repair in patients with CAAs.

What does the data show on endovascular treatment vs. open surgery?

In a recent article by Shukla et al. comparing outcomes between endovascular treatment (n = 122) and open surgery (n = 59) for VAAs, results show that endovascular treatment and open surgery are equally durable for patients with intact VAA, but endovascular treatment for ruptured VAAs was associated with a lower 30- day mortality rate (7.4% vs 28.6%; p<0.05) and better 2-year overall survival (69.4% vs 46.4%; p<0.05).

Questions to Consider

What are possible complications of CAA aneurysms and Stent Grafts for the CAA?

As mentioned above, the most dangerous complication of untreated CAAs is life-threatening hemorrhage. However, endovascular treatment of CAAs with stent grafts carries its own set of risks including dissection, stent thrombosis with end-organ ischemia, splenic infarction, and endoleaks.

While performing an endovascular Stent Grafting of a CAA, what do you have to watch for?

The anatomy of celiac artery aneurysms is complex, given that multiple branches can exit the aneuryms. Without identifying and potentially embolizing relevant branches, endoleaks may develop after stent graft placement. Equally, the interventionalist must define the distal landing zone for the endograft to assure a good seal and likelihood of long term patency. Pre-procedure planning with CTA and detailed catheter angiography are of utmost importance. As mentioned previously, endoleaks are of a concern as well, however, none resulted in the cases presented in the manuscript above. Many CAAs are associated with median arcuate ligament compression and post-stenotic dilation. Ligamentous compression may permanently deform balloon expandable stent grafts,

What are the limitations of the above study and why?

While the study sample was small (n=10), given low prevalence of the disease, this is nevertheless a meaningful number to show safety and efficacy. In addition, the retrospective nature introduces the possibility of selection bias. Can all CAAs be treated with stent graft? What can preclude a CAA from stent graft repair? If a CAA may be treated by embolization or stent graft, how should we decide the optimal treatment approach? 

What are the different types of Endoleaks?

While the classification system for endoleaks was originally intended for and applied to abdominal aortic aneurysms (AAAs), it can be used for discussion regarding stent graft treatment for aneurysm exclusion in other vascular territories.

Type I: Persistent filling of the aneurysm sac due to incomplete seal at the proximal or distal end of the stent graft.
Type II: Persistent filling of the aneurysm sack due to retrograde branch flow from collateral vessels.
Type III: Blood flow into the aneurysm sac due to ineffective sealing of overlapping graft joints.
Type IV: Blood flow into the aneurysm sac due to the porosity of the graft fabric, causing blood to pass through the graft joints or rupture of graft fabric.
Type V: Aneurysm sac expansion without clear evidence of endoleak origin.

Additional citations:
Shukla AJ, Eid R, Fish L, et al. Contemporary outcomes of intact and ruptured visceral artery aneurysms. J Vasc Surg 2015; 61:1442–1448.

Post author:
Ali Alikhani, MD
Diagnostic Radiology Resident, PGY-4
University of Tennessee Methodist Healthcare