New Prospective Evaluation of Intraarterial Lidocaine During UAE

Pain control during the post-procedural period remains one of the persistent challenges of uterine artery embolization (UAE). Noel-Lamy et al present the results of a prospective randomized clinical trial comparing the efficacy of intra-arterial (IA) lidocaine infusion for pain control after UAE. Sixty patients were randomized to three arms, each with 20 patients: group A - 1% lidocaine infused with the first polyvinyl alcohol (PVA) vial during embolization followed by additional PVA vials to the embolization endpoint, group B – 1% lidocaine infused after PVA embolization to the embolization endpoint, and group C – control group for which saline was infused. The primary outcome was pain score using a validated scale at 4 hours post-UAE, which was significantly lower for the IA infusion groups (group A: infusion during PVA embolization, 28.6, SD: 24.5; group B: infusion post PVA embolization 35.8, SD: 22.6) versus control (59.4, SD: 30.3), p=0.001. This significant difference in pain levels dissipated by the 7 hour and 24 hour post-UAE time points, which were secondary outcomes. The in-hospital narcotic dose was significantly less for the lidocaine infusion groups (group A: 8.5 mg, SD: 7.4; group B: 11.1 mg, SD: 7.6) compared to control (17.4 mg, SD: 10.5), p=0.006. The 24-hour narcotic dose was also significantly less for the lidocaine infusion groups (group A: 11.1, SD: 9.6; group B: 16.3, SD: 11.5) compared to control (21, SD: 10.5), p=0.021. No significant difference in time to discharge was observed between groups. On 3-month post-UAE MRI, there was a significantly lower rate of complete infarction in group A (38.9%) versus group B (77.8%) or control (75%), p=0.045. There were no serious adverse events in any of the treatment arms.

Commentary

This study by Noel-Lamey et al provides a well-designed, prospective evaluation to confirm the efficacy of IA lidocaine infusion for pain control following UAE. The authors used a validated pain scale to provide a more reliable and replicable endpoint measure than previous studies using non-validated pain scores. Their results suggest that IA lidocaine infusion does provide significant analgesic benefit during the immediate post-procedural period, to a degree that is sufficient to reduce the oral narcotic requirement in the first 24 hours. It is important to note that the standard deviations for both the pain scale measures and the narcotic doses were relatively wide, perhaps reflecting inherent differences in pain perception between patients. Interestingly, the degree of analgesia was not significantly different between lidocaine infusion with initial embolization or following embolization, even as the authors acknowledged that most of the infusion likely refluxed from the uterine arteries in the latter approach. Previous studies have shown severe vasospasm with lidocaine infusion during embolization, which was not observed in this study, likely due to usage of a lower lidocaine dose. However, there was a 50% lower percentage of complete fibroid infarction at 3 months post-UAE in the group that received lidocaine with initial embolization versus post embolization, suggesting that distal vasospasm occurred and partially interrupted embolic delivery. Based on these findings, the authors concluded that lidocaine infusion after embolization is preferable to during embolization. Limitations to this study included the lack of investigator blinding to the method of lidocaine injection, narcotic administration by a nurse rather than patient controlled analgesia, and relatively small sample size. Nonetheless, while additional investigation should be done, the study effectively confirms the efficacy and safety of IA lidocaine infusion for UAE pain control and clarifies the optimal infusion timing relative to embolization.

Click here for abstract

Noel-Lamy M, Tan KT, Simons ME, Sniderman KW, Mironov O, Rajan DK. Intraarterial Lidocaine for Pain Control in Uterine Artery Embolization: A Prospective, Randomized Study. J Vasc Interv Radiol 2016. Article in press.

Post Authors:
Jeffrey Forris Beecham Chick, MD, MPH, DABR
Assistant Professor of Vascular and Interventional Radiology
Vice Quality Assurance and Safety Officer
University of Michigan Health Systems

James X. Chen, MD
Resident in Radiology
Hospital of the University of Pennsylvania

From the SIR Residents and Fellows Section (RFS)

Teaching Topic: Treatment of In-Stent Restenosis in Patients with Renal Artery Stenosis

Takahashi E A, McKusick M A, Bjarnason H, Piryani A, Harmsen W S, Misra, S. Treatment of In-Stent Restenosis in Patients with Renal Artery Stenosis. J Vasc Interv Radiol. 2016. 27 (11): 1657 - 1662.

Click here for abstract

In the November 2016 issue of JVIR, a retrospective study examined the clinical outcomes of patients treated for renal artery in-stent restenosis (ISR) with atherosclerotic renal artery stenosis was evaluated. 1,090 renal artery stents were placed in 1,052 patients, with an average patient age of 73.6 years +/- 8.3. in 79 patients, 101 bare metal stents developed ISR, and the patients underwent repeat stent placement vs. angioplasty. Diagnosis of ISR was mainly done via duplex ultrasound. Percutaneous Transluminal Angioplasty and or stent placement was performed. If the patient did not have >30% residual stenosis on follow-angiogram or a mean pressure gradient of < 10 mm Hg, the patient received no further treatment. Otherwise, a bare metal balloon expandable stent was used, with exception of using DES in a small group of patients.

Of the 1,090 renal artery stents, 101 developed ISR. Bilateral ISR was identified and treated in 27.8% of patients. Renal arteries with ISR treated with repeat stent placement were 6.89 times more likely to develop restenosis requiring a repeat procedure compared with arteries treated with PTA (P < 0.01). None of the arteries that received DES during repeat stent placement developed significant restenosis. The study did demonstrate a statistically significant decrease in both SBP and DBP after re-intervention. Of the 101 renal arteries treated for ISR, 13 developed secondary ISR. After ISR treatment, serum creatinine levels improved by a statistically insignificant amount.

In conclusion, treatment of renal artery ISR with PTA among patients with atherosclerotic renal artery stenosis has a lower rate of subsequent ISR compared with repeat stent placement.

Clinical Pearls

1. What is a serious potential setback with renal artery stent placement in patients with atherosclerotic RAS?

When a stent is inserted in an artery, the internal elastic lamina becomes disrupted. This results in smooth muscle cell migration and intimal hyperplasia. These intimal lesions incorporate atherosclerotic elements leading to ISR. In turn, intractable hypertension and renal insufficiency may arise secondary to ISR.

2. Did stent diameter contribute to the rate of restenosis?

The stent or PTA diameter did not have a statistically significant association with renal artery patency. However, there tended to be fewer cases of restenosis with stents or PTA diameters > 5.0 mm. Other studies also found that stent diameter was not a significant predictor of recurrent ISR events, although a similar trend can be seen with increasing vessel diameter related to decreased ISR.

Questions to Consider

1. What are the two main causes of renal artery stenosis and eventual renovascular hypertension (RVH)?

Atherosclerotic disease and FMD (Fibromuscular Dysplasia).

Other causes include trauma, renal cystic disease, renal cell carcinoma, pheochromocytoma, renal artery aneurysm, reninoma, vasculitis, extrinsic compression and renal infarction.





Source: www.cvphysiology.com

2. What are the imaging modality methods of diagnosing RAS?

Ultrasound with color doppler is the principal tool for detecting RAS / RVH because it is quick, relatively inexpensive and safe. Criteria for significant renal artery stenosis include intrastenotic peak systolic velocity (PSV) of greater than 180 cm/sec and PSV renal/aortic ratio of greater than 3.0 to 3.5.

CT and MRI have been used as a screening exam in some centers, especially if renal function is close to normal. MR Angiography can detect up to 90% to 100% sensitivity and 75-100% specificity. Weaknesses of the method include identification of disease in accessory and segmental renal arteries and artifacts related to metallic clips, intravascular stents or patient motion. Multidetector row CT angiography achieves comparable sensitivity and specificity to MR angiography in depicting renal artery stenosis.

Renal vein sampling measures renin activity in the renal vein vs. the IVC. In a patient with RVH and two functioning kidneys, the affected kidney overproduces renin, and the renin production of the contralateral kidney is reduced. Renal vein renin ratio between the involved and uninvolved kidney of greater than 1.5 and a ratio of (renal renin – IVC renin) / IVC renin of > 0.48 is indicative of RVH.

Lastly, catheter angiography is the gold standard for the diagnosis of RAS. This method allows direct and live visualization of the renal arterial narrowing under fluoroscopic guidance. Hemodynamic significance is proved by the following criteria:

• Reduction in luminal diameter of > 75%. 
• Systolic pressure gradient cross stenosis in the main renal artery greater than 10-20mm hg or greater than 20% of aortic systolic pressure. 
• A stenosis with a 50-75% reduction in luminal diameter may be hemodynamically significant, but in such cases, pressures should be measured. 

Other sources used: The Practice of Interventional Radiology by Karim Valji

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

It's All in the PROBIO: 12-month Results of the Nitinol Astron Stent in Iliac Artery Lesions 

Multiple stents are currently on the market for use in treating iliac atherosclerotic occlusions, but the optimal system remains to be determined. Burket et al. present the results of a prospective registry evaluating the safety and efficacy of the Astron stent (Biotronik; Bulach, Switzerland), a new amorphous silicon carbide (PROBIO)-coated nitinol self-expanding stent, in treatment of iliac occlusive disease. The PROBIO coating reduces metal ion release, which decreases stent thrombogenicity and promotes endothelialization. 161 patients underwent stent placement at 30 sites, of whom 145 patients completed 12-month study follow-up. The patient demographics and comorbidities as well as iliac lesion characteristics were comparable with other similar stent studies. The primary endpoint, a composite major adverse event (MAE) rate, including 30-day all-cause mortality, 12-month target lesion revascularization (TLR) rate, and 12-month index limb amputation, demonstrated a MAE rate of 2.1%, which was well within the performance goal of 15% (determined based on results of prior similar stent studies). The secondary outcomes included primary patency rate at 12-months (89.8%), freedom from target vessel revascularization (97.9%), freedom from bypass or amputation at 12-months (100%), and acute and 30-day technical success rates (95% for both metrics). ABI increased by a mean of 0.23 (p<0.001) and 6-minute walk increased by a mean of 158 feet (p<0.001) after stenting. Technical adverse events occurred in four cases, including uneven stent expansion (n=2), stent misplacement (n=1), and failure to deliver the stent at the intended site (n=1).

Commentary

The results of this prospective registry demonstrated promising efficacy and a favorable safety profile for the Astron stent in treating iliac occlusive disease. Although the 12-month composite MAE of 2.1% was similar to the range of results seen in other stent models (2.2-7.5%), direct comparisons were hampered by heterogeneity in MAE score definition between studies, and additional studies (ideally prospective randomized controlled trials with standardized endpoints) are necessary to elucidate the optimal stent device for iliac occlusive disease. Given known durability of iliac stenting and previous studies with freedom of 92% at 48 month2, long term outcomes beyond 12-months will also be important to determine durability of this stent, and may provide additional clarification on the potential real-world benefits of silicon carbide-coating versus non-silicon carbide coating for iliac arterial stenting. In the discussion, the authors referred to the CLEVER trial, which demonstrated similar efficacy between supervised exercise and stenting, a finding which raises fundamental questions regarding the risk and benefit ratio of endovascular intervention in these patients. These results are an important consideration for future iliac occlusive disease study designs, which may need to not only compare outcomes between multiple stent models, but also against supervised exercise testing, to best define the optimal treatment paradigm.

Click here for abstract

1. Burket MW, Brodmann M, Metzger C, Tan K, Jaff MR. Twelve-Month Results of the Nitinol Astron Stent in Iliac Artery Lesions. J Vasc Interv Radiol 2016; 27: 1650-1656.

2. Sabri SS, et al. Outcomes of covered kissing stent placement compared with bare metal stent placement in the treatment of atherosclerotic occlusive disease at the aortic bifurcation. J Vasc Interv Radiol 2010; 21: 995-1003.

Post Authors:
Jeffrey Forris Beecham Chick, MD, MPH, DABR
Assistant Professor of Vascular and Interventional Radiology
Vice Quality Assurance and Safety Officer
University of Michigan Health Systems

James X. Chen, MD
Resident in Radiology
Hospital of the University of Pennsylvania

From the SIR Residents and Fellows Section (RFS)

Teaching Topic: Transradial Approach for Noncoronary Interventions: A Single-Center Review of Safety and Feasibility in the First 1,500 Cases

Posham R, Biederman DM, Patel RS, Kim E, Tabori NE, Nowakowski FS, Lookstein RA, Fischman AM. J Vasc Interv Radiol 2016; 27:159-66.

Click Here for Abstract

Transradial access (TRA) is an increasingly common method of performing percutaneous intravascular interventions. Although the interventional cardiology literature has described the benefits of TRA in large prospective studies, the data for TRA in noncoronary interventions is sparse. In this study, a retrospective analysis was performed on 946 patients for 1,531 consecutive procedures using transradial access for noncoronary interventions. Exclusion criteria included sheath sizes >6Fr, Barbeau D waveform, radial artery <2mm, known severe aortic tortuosity, dialysis, and radial artery occlusion. Reported results included success rates of 98.2% with minor and major complication rates of 2.38% and 0.13%, respectively. Endoleak repair and renal/visceral intervention were the only significant predictors of cross over to transfemoral access (TFA). Limitations were stated to be non-randomization of the population, operator proficiency bias, and subclinical complications.

Clinical Pearls

What is the Barbeau classification of pulse waveform and how is it used in selecting eligible patients for TRA?

Radial access is a theoretically feasible approach due to the vascular anatomy of the hand. The hand is supplied by both the ulnar and radial artery. There is collateral flow between arteries via the deep and superficial arches as well as the interosseous collaterals. The Barbeau classification of pulse wave forms is an objective test (adaption of the modified Allen test), which indirectly assess the integrity of the collateral circulation between both arteries. To perform this test, a pulse oximetry device is placed on the thumb and the morphology of a plethysmography tracing is noted. The examiner subsequently occludes the radial artery and observes the waveform over a two minute period (see Figure 1 of article).

· A type A response does not demonstrate a change in the waveform (uninterrupted arterial filling) after occlusion.

· A type B response does not demonstrate interrupted arterial filling, however, there is decreased amplitude of the waveform with adaption and restoration of the previous (unconcluded) waveform by two minutes.

· A type C response demonstrates interrupted arterial filling (cessation of pulsatile waveform) with subsequent delayed appearance of a pulsatile waveform. This is thought to be secondary to recruitment of collaterals.

· A type D response demonstrates interrupted arterial filling, however, there is no restoration of visualized pulsatile collateral flow at two minutes.

What is the standard radial access technique?

Topical nitroglycerine and lidocaine are applied to the wrist 30 minutes prior to cannulation. Preferentially, the left wrist is cannulated. A wrist towel roll is places beneath the wrist to allow for adequate hyperextension. Patient can be positioned prone or supine. Pulse oximeter is applied to the ipsilateral thumb or index finger. After radial access is obtained, a hydrophilic sheath is placed (4-7Fr with preference for smaller sheaths). Catheter lengths of 110 cm with standard 0.035-in access wire are used for engaging the mesenteric vessels. Microcatheters are typically 150 cm. Nonocclusive hemostasis is utilized to decrease risk of radial artery occlusion at the conclusion of the procedure.

Questions to Consider

What are the proposed benefits of TRA versus TFA?

The RIFLE study demonstrated a decrease in access site-related bleeding, net adverse events (in PCI), and decreased length of hospital stays. The RIVAL study, a multicenter prospective randomized controlled trial, showed a decrease in major vascular complications in the TRA arm. TRA also provides for easier hemostasis, the option of earlier ambulation, and increased reported patient satisfaction. Finally, TRA has also been shown in one study to be overall more cost effective.

What complications should be specifically mentioned in the consent process when considering TRA?

Radial artery occlusion (RAO) is a known complication of TRA thought to be secondary to intimal disruption which is reversible and asymptomatic in most subjects. Symptomatic RAO has been reported at 0.2% with digital ischemia being a severe presentation of such. The radial artery is also subject to spasm. The risk of cerebrovascular infection is theoretically increased (although debated) due to proximity to the vertebral artery and necessary aortic arch manipulation. However, this is mediated by preferentially cannulating the left wrist to decrease arch manipulation. Other complications include hematoma, pain, pseudoaneurysm, perforation, and dissection which are also risks of TFA.

Additional References:
Kotowycz MA, Dzavík V. Advances in Interventional Cardiology. Circ Cardiovasc Interv. 2012 Feb 1;5(1):127-33.

Fischman AM, Swinburne NC, Patel RS. A Technical Guide Describing the Use of Transradial Access Technique for Endovascular Interventions. Tech Vasc Interv Radiol. 2015 Jun;18(2):58-65

Post Author:
Lindsay Karr Thornton, MD
SIR RFS Clinical Education Chair
University of Florida

5-Year Results of Laser-Assisted Vena Cava Filter Removal

Inferior vena cava (IVC) filters with prolonged implantation are associated with increased risk of filter-related complications. Prolonged dwell time is also associated with an increased risk of the filter embedding in the vessel wall increasing the likelihood of failed retrieval using standard retrieval methods. Kuo et al. recently published their 5-year results of laser-assisted removal of embedded IVC filters in the journal CHEST. A total of 251 patients were enrolled prospectively in the study after failure of standard retrieval methods. Indications for filter retrieval included symptomatic IVC thrombosis, chronic IVC occlusion, pain from filter penetration and/or reduction of risk from prolonged implantation. Success was defined as complete filter detachment and removal. Major procedure-related complications were assessed. Laser-assisted retrieval was successful in 249/251 (99.2%) with a mean dwell time of 979 days (range 37-9098). Less measured force was needed for laser-assisted retrieval compared to failed standard retrieval attempts (3.8 lbs compared to 6.7 lbs). They report a major complication rate of 1.6%. This included 2 patients who developed IVC thrombus during the procedure that was successfully treated with catheter-directed thrombolysis and 2 patients who suffered IVC injury with retroperitoneal hemorrhage and hypotension requiring endovascular stentgraft placement. Retrieval permitted a cessation of anticoagulation in 45/46 (98%) patients. Filter associated morbidity was relieved in 55/57 (96%) patients. Authors conclude the excimer laser-sheath technique is safe and effective for removing embedded IVC filters that have failed standard retrieval attempts.

Commentary

This article reports favorable results for the use of the excimer laser sheath for IVC filter retrieval that has failed standard techniques. The laser sheath is FDA approved for removal of embedded venous pacemaker leads and any use for embedded IVC filters is off-label. Failed laser-assisted retrieval occurred with cylindrical-shaped filters (1 Optease and 1 Trapease) that contained a large amount of chronic thrombus that could not be captured within the sheath. In subsequent cases, authors reduced large amounts of chronic thrombus with a separate atherectomy catheter and/or angioplasty balloon allowing for laser-assisted filter removal. Not included in the major complications were 25 patients that developed a small (<2.5 cm) pseudoaneursym and 3 patients with small focal hemorrhage. All were self-limited or treated with temporary occlusion balloon inflation with resolution on immediate follow-up venography. Pseudoaneurysms larger than 2.5 cm were followed with cross sectional imaging and found to be resolved within 2-3 months. Data for this study was collected over a 5-year time period and authors do admit to a learning curve with laser sheath usage. Prior to routine force gauge use there were 4 cases of laser sheath cracking external to the patient with application of excessive force. Additionally, the major complications reported occurred earlier in their experience. The encouraging overall safety and efficacy, therefore, may not be transferable to early experience.

Click here for abstract

Kuo WT, Odegaard JI, Rosenberg JK, Hofmann LV, Laser-Assisted Removal of Embedded Vena Cava Filters: A 5-Year First-in-Human Study, CHEST (2016), doi: 10.1016/j.chest.2016.09.029.

Post Author:
Jennifer Montgomey, MD, PhD
Assistant Professor
Cleveland Clinic

From the SIR Residents and Fellows Section (RFS)

Teaching Topic: The Influence of Statin Therapy on Restenosis in Patients Undergoing Nitinol Stent Implantation for de Novo Femoropopliteal Artery Disease

Kim W, Gandhi RT, Peña CS, Herrera RE, Schernthaner MB, Acuña JM, Becerra VN, Katzen BT. The Influence of Statin Therapy on Restenosis in Patients Who Underwent Nitinol Stent Implantation for de Novo Femoropopliteal Artery Disease: Two-Year Follow-up at a Single Center. J Vasc Interv Radiol 2016; 27:1494–1501

Click here for abstract

Peripheral artery disease (PAD), including femoropopliteal artery disease, has been proposed as a “coronary heart disease risk equivalent” in the National Cholesterol Education Program Adult Treatment Panel III. Patients with femoropopliteal arterial disease are strong candidates for statin therapy. The effect of statin therapy on femoropopliteal arterial disease has received relatively little attention in the literature. This manuscript evaluated 135 limbs in 135 patients in whom nitinol stents were placed in femoropopliteal occlusions and found that the incidence of binary restenosis was significantly lower in the statin group than in the nonstatin group.

Clinical Pearls

What are the TransAtlantic Inter-Society Concensus (TASC) II classifications of femoral popliteal lesions?
The following diagram illustrates the TASC II classification of femoropoliteal disease as described by Norgren et al. in the Journal of Vascular Surgery in January of 2007.



This study aimed for goals of a residual pressure gradient of less than 10 mm Hg, residual stenosis of less than 30%, or no flow-limiting dissection after nitinol stent implantation according to TASC II. 91.1% of lesions treated in this study were TASC II type C or D.


What are the American College of Cardiology and American Heart Association guidelines for intensity of statin therapy?

The “2013 ACC/AHA Guideline on the Treatment of Blood Cholesterol to Reduce Atherosclerotic Cardiovascular Risk in Adults” established algorithms to decide initiation and dosing of statin therapy.  

Click here for the complete report

What are the pharmacologic effects of statins?

Statins have potent pleiotropic effects in addition to their lipid-lowering effects, such as reducing inflammatory response and oxidative stress, protecting vascular endothelial function, inhibiting the proliferation and migration of vascular smooth muscle cells, and inhibiting neointimal hyperplasia.

Morning Report Questions

What were the methods to follow-up patients after femoropopliteal revascularization with nitinol stenting?

The authors in this study evaluated patients for follow-up within 30 days of the index procedure, which included an assessment of the patient’s clinical improvement as well as interval ankle-brachial index (ABI) and duplex ultrasound (US) scanning. Follow-up was then conducted every 3–6 months during the first postoperative year and every 6–12 months thereafter. In cases of suspected restenosis based on the clinical evaluation and arterial noninvasive examination, lower-extremity computed tomographic angiography could be performed at the discretion of the operator. The primary endpoint of the study was binary restenosis (angiographic luminal narrowing > 50% in diameter anywhere within the stent or within the 5-mm proximal or distal border of the stent or peak systolic velocity ratio of > 2.54 by duplex US) at 1 year. Secondary endpoints were primary patency at 1 year, binary restenosis at 2 years, and target lesion revascularization (TLR; repeat revascularization of the target lesion secondary to restenosis of more than 50% within the stent or 5 mm proximal or distal to the stent) at 2 years

In the present study, a total of 135 limbs (91.1% TASC II type C or D lesions) of 135 patients were included in the analysis. 91 (67.4%) received statin therapy and 44 (32.6%) did not. Equivalent proportions of patients in each group were treated with aspirin, thienopyridine derivatives, and cilostazol. The total stent implanted length and mean stent diameter did not differ between groups. The mean follow-up duration was 16.9 months. There were significant differences in the incidence of binary restenosis between groups at 1 year (45.5% for the nonstatin group vs 28.6% for the statin group; P = .05) and 2 years. Primary patency rates at 1 year were 50.5% in the nonstatin group and 72.5% in the statin group (P = .01). The 2-year TLR rates were 54.5% in the nonstatin group and 35.2% in the statin group (P = .03). The odds of binary restenosis at 1 year were not affected after adjustment for age, sex, and other cardiovascular risk factors.

What is the mechanism of cilostazol and how might it have confounded the study?

Cilostazol is a phosphodiesterase (PDE) III inhibitor with vasodilator, metabolic, and antiplatelet activity. The TASC II analysis reported benefits of cilostazol over placebo in treadmill performance and quality of life measures with side effects of headache, diarrhea, and palpitations. Because it is a PDE III inhibitor, it should not be given to patients with congestive heart failure. Recent studies have demonstrated that that long-term cilostazol therapy was able to reduce restenosis after endovascular therapy in symptomatic patients with femoropopliteal artery disease. Although the use of cilostazol was statistically equivalent between the two groups in the present study, the rates of binary restenosis and TLR might be affected according to the proportion of patients receiving cilostazol therapy.

How may future studies be affected by increasing statin use?

Some patients in the nonstatin group of this study included those with hypertension, CAD, or a history of percutaneous coronary intervention. It is possible that these and other patients with transient ischemic attack or minimal coronary artery stenosis may have been followed up without the use of statins, even though that is not considered the standard of care. The Reduction of Atherothrombosis for Continued Health Registry showed that the rate of statin use at baseline was only 62.2% in patients with PAD, and one third of the nonstatin group had a history of CAD or cerebrovascular disease. They observed differences in statin use based on physician subspecialty or patient age. The use of statins has become more common, but a high prevalence of statin use among patients with PAD in the future will make it challenging to design clinical studies to evaluate the role of statin therapy as an inhibitor of restenosis after nitinol stent implantation in patients with femoropopliteal artery disease.

Additional Citations:
Norgren et al. Inter-Society Concensus for the Management of Peripheral Arterial Disease (TASC II). Journal of Vascular Surgery. 2007 January; 45(1): S5A-S67A

Stone NJ, Robinson JG, Lichtenstein AH, et al. 2013 ACC/AHA guideline on the treatment of blood cholesterol to reduce atherosclerotic cardiovascular risk in adults: a Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation 2014; 129(25 Suppl 2):S1–45.

Post Author:
Rajat Chand, MD
Diagnostic Radiology Resident, PGY-2
John H. Stroger Hospital of Cook County

Meta-analysis of Prostate Artery Embolization

There is increasing data on outcomes of prostate artery embolization (PAE) for benign prostatic hyperplasia (BPH), but there remains a need for more robust evaluation of this new intervention. Uflacker et al performed a meta-analysis of available PAE studies, including studies which reported standardized urologic and clinical outcomes, and excluding studies which included redundant cases. Six of 268 studies met these criteria, and were analyzed for primary outcomes of International Prostate Symptom Score (IPSS) and Quality of Life (QoL) score. At 1, 3, 6, and 12-months post PAE, there were significant decreases in both scores from baseline values (p < 0.001); the IPSS scores decreased 12.93, 14.98, 15.00 and 20.39 points and the QoL scores decreased 2.17, 2.18, 2.15, and 2.49 points at the respective times points. Secondary outcomes included changes in prostate volume (PV), post void residual (PVR) and International Index of Erectile Function (IIEF) score. Prostate volumes demonstrated significant progressive decreases from baseline, including 62.0 mL at 1-month (p < 0.004) and 85.5 mL at 12-months (p < 0.001) post PAE. Qmax also demonstrated durable improvement, of 4.7 mL/s at 1-month, and 5.4 mL/s at 12-months post PAE (p < 0.001). There was no significant change in the IIEF score at the various time points, up to 12=months post PAE. Complications were also analyzed from nine studies, which revealed a 32.9% complication rate, nearly all of which were minor complications (216/218). The two major complications were severe urinary tract infection and bladder ischemia.

Commentary

As the authors highlighted in their introduction, there have been numerous challenges to interpreting previous meta-analyses on PAE literature, due to the inclusion of studies with redundant cases. The efforts in this study design to avoid those confounding factors and attain patient-level data, when possible, afforded a cleaner, potentially more valid, evaluation of existing PAE data. The improvements in the primary endpoints of IPSS and QoL as well as secondary endpoints including Qmax seen at up to 12-months after PAE, across the analyzed studies supported the efficacy and durability of PAE, while the exceedingly low rate of major complications also suggested a favorable safety profile. There are numerous limitations to the meta-analysis results, which the authors described in the discussion, including heterogeneity in patient populations and technical approaches between studies, as well as drop-offs in data for the longer post-PAE time points (i.e. 12-month versus 1-month). These factors precluded reliable elucidation of controversial issues including optimal embolic size/agent and unilateral versus bilateral embolization. Outcome comparisons with existing urologic interventions for BPH including transurethral resection of the prostate (TURP) and transurethral holmium laser enucleation (HoLEP) were also not addressed by this meta-analysis. Ongoing and future randomized controlled trials and registries will be essential to provide definitive answers to these questions and delineate the optimal role of PAE in BPH management. Nonetheless, this meta-analysis provides an improved evaluation of currently available evidence on this promising intervention for BPH.

Click here for abstract

Uflacker A, Haskal ZJ, Bilhim T, Patrie J, Huber T, Pisco JM. Meta-Analysis of Prostatic Artery Embolization for Benign Prostatic Hyperplasia. J Vasc Interv Radiol. 2016; 27: 1686-1697.

Post Authors:
Jeffrey Forris Beecham Chick, MD, MPH, DABR
Assistant Professor of Vascular and Interventional Radiology
Vice Quality Assurance and Safety Officer
University of Michigan Health Systems

James X. Chen, MD
Resident in Radiology
Hospital of the University of Pennsylvania

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.

Click here for abstract

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.



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

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

Click here for full text

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
@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.

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

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

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