From the SIR Residents and Fellows Section (RFS)

Teaching Topic: Portal Vein Embolization via Percutaneous Transsplenic Access prior to Major Hepatectomy for Patients with Insufficient Future Liver Remnant

Ko HK, Ko G, Sung K, Gwon D, Yoon H. Portla vein embolization via percutaneous transsplenic access prior to major hepatectomy for patients with insufficient future liver remnant. J Vasc Interv Radiol 2016; 27:981–986.

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In this recent article from JVIR, researchers evaluated the feasibility and safety of utilizing a transsplenic approach for portal vein embolization (PVE). The transsplenic approach was used in 16 patients due to anatomic difficulty secondary to tumor burden or trajectory of transhepatic access. In the remaining patients, a planned transsplenic approach was chosen prior to the start of the procedure. Embolization was performed with gelatin sponge particles followed by coils, amplatzer vascular plugs, or glue. There were 3 of 27 failed transsplenic accesses dues to splenic vein dissection (n=1) or failed splenic vein puncture (n=2). The remaining patients had successful planned liver resection at 4.9+/-3.5 weeks. The authors conclude that transsplenic PVE may be considered a safe and feasible treatment option in patients that have contraindications to a traditional ipsilateral approach.

Clinical Pearls

What patient population would benefit from portal vein embolization?

The patient population that benefit from portal vein embolization are those who are at significant risk of fulminant hepatic failure following total right hepatectomy for tumor resection due to the fact that their liver remnant following surgery is too small to function properly for the patient. In order to increase the size of this future liver remnant, portal vein embolization can be utilized to capitalize on the liver’s unique regenerative ability and increase the future liver remnant volume. The ratio of future liver remnant to total liver volume should be >40% in patients with chronic liver disease.

What are some contraindications to PVE?

While there are no absolute contraindications for PVE, there are a number of relative contraindications. Clearly metastatic disease with distal involvement or metastatic disease involving segment I, II, or III or involving the entire left lobe and segment VI or VII are not candidates for right or left trisegmentectomy, respectively and would not benefit from PVE. Other relative contraindications include biliary dilation, uncorrectable coagulopathy, tumor invasion of the portal vein, portal hypertension, and portal vein thrombus in the contralateral portal vein.

Morning Report Questions

How is the FLR calculated?

The percentage of liver left behind after surgery (future liver remnant, FLR) is a strong, independent predictor of postsurgical hepatic dysfunction and complications. CT with volumetrics is the cornerstone for planning surgical resection. There are different methods of calculating liver volumes. Many institutions will directly measure the FLR and estimate the TELV with a formula based on the patient’s body weight and body surface area (TELV = -794.41 + 1267.28 (BSA)) so that the FLR/TELV ratio can be calculated. This method allows uniform comparison of FLR volume prior to extended resection with or without preoperative PVE.

What are the embolic agents that can be used for PVE?

A variety of embolic agents may be used in PVE. Many have been investigated and show similar levels of effectiveness. Agents include: N-butyl cyanoacrylate (NBCA) & lipiodol; ethanol; PVA or Embospheres with coils or Amplatzer vascular plugs. A recent article from Jaberi et al. compared NBCA + AVP with PVA ± coils and found a greater degree of hypertrophy of the FLR, less fluoroscopic time and contrast volume, and similar complication rates. However, a full cost analysis and additional studies may need to be performed prior to any significant change in practice pattern.

What are the benefits and drawbacks for the various approach methods for portal vein embolization?

The standard approach method for portal vein embolization is the ipsilateral transhepatic approach (i.e. approaching from the same side of the liver that you are planning to embolize). The benefit of this approach is that you avoid damage to the future liver remnant. However, with the ipsilateral approach, there is increased risk of tumor seeding if there is a large tumor burden or a tumor lies within the trajectory of the puncture. Infection is also a concern as there is a risk of bile duct puncture.

The next most common is a contralateral transhepatic approach. The benefit with the contralateral approach is that you avoid possible tumor seeding of the tract. However, this runs the risk of damage to the future liver remnant as you are traversing the normal liver that you hope to maintain and grow. As with the ipsilateral approach, infection is a concern due to possible puncture of bile ducts.

Transsplenic approach is beneficial as it allows for avoidance of tumor seeding, damage to the future liver remnant and infection from bile duct puncture. However, the main drawback of a transsplenic approach is the risk of bleeding. The spleen is a highly vascular organ and small injuries can lead to significant bleeding. As can be seen in this associated manuscript, further investigation is warranted.

Additional Citations:
Jaberi A, et al. Comparison of clinical outcomes following glue versus polyvinyl alcohol portal vein embolization for hypertrophy of the future liver remnant prior to right hepatectomy. J Vasc Interv Radiol 2016. In press.

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

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.

Commentary

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.



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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

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

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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.

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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
@lukewilkins_UVA

FROM THE SIR RESIDENTS AND FELLOWS SECTION (RFS)

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.

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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.

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

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

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.

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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