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Thursday, January 26, 2017

From the SIR Residents and Fellows Section (RFS)


Teaching Topic: Cryoneurolysis in Patients with Refractory Chronic Peripheral Neuropathic Pain


Yoon JH, Grechushkin V, Chaudhry A, Bhattacharji P, Durkin B, Moore W. J Vasc Interv Radiol. 2016 Feb;27(2):239-43. doi: 10.1016/j.jvir.2015.11.027.

Click Here for Abstract

Approximately, 15 million people in the United States and Europe experience chronic neuropathic pain. In the current climate, non-opiate based pain control is a topic of discussion among doctors and patients as well as at the national level among politicians. Therefore, studies showing efficacy of percutaneous interventions for the purpose of pain alleviation are paramount. In this study, the authors performed ultrasound guided cryoneurolysis on 22 patients with refractory peripheral neuropathic pain. Mean pain levels were 8.3 +/- 1.9 prior to intervention with a statistically significant decrease in mean pain scores at 1, 3, 6, and 12 months post procedure with repeat intervention required in 50%. This suggests this method may be efficacious for moderate term pain relief. Limitations of the study included small sample size and non-uniform concurrent pain regimens. However, the results are quite promising given the positive response to therapy and the superior safety profile of cryoneurolysis compared to alternative invasive therapies for the treatment of neuropathic pain.

Clinical Pearls


What is the basic pathophysiology of pain generation?


Nociceptors in the tissue convert a noxious stimuli to an electric impulse signaling an efferent nerve. This signal travels to the dorsal root ganglion and ascend centrally via the spinothalamic tract. Glutamate is thought to be involved in signaling at this level. The electrical signaling continues to the thalamus where it then relays the stimulus to various centers in the brain including the primary sensory cortex, periaqueductal grey, amygdala, pons and reticular formation in the brainstem among others. Under normal circumstances, inhibitory pathways in the periaqueductal grey and Lissauer tract release endogenous opioids, norepinephrine (NE), and serotonin mediated by GABA inhibitory neurons to mediate the perceived pain.

What is the pathophysiology of Cryoneurolysis on the peripheral nerve?

Temperatures of at least -30°C causes axonotmesis (disruption of the axon) and results in Wallerian degeneration of the nerve distal and slightly proximal to the induced thermal injury. There is preservation of the perineurium and epineurium and, therefore, regeneration of the nerve may occur over time. According to the authors, some studies show that the time for nerve regeneration is proportional to length of cryoablation.

Questions to Consider


What are other common percutaneous interventions available for neuropathic pain and what are their drawbacks?

Percutaneous nerve blocks are among the most common types of anesthesia for neuropathic pain. This technique typically employs a steroid/analgesic concoction to chemically decrease inflammation and axonal conduction, respectively. Drawbacks include: relatively short term relief, adverse systemic effects of corticosteroids, and possible nerve damage with subsequent neuritis.

Thermal ablation including microwave ablation and radiofrequency ablation/pulsed radiofrequency ablation cause tissue/nerve necrosis at predictable temperatures. Arguably, there is increased risk of thermal injury to potentially sensitive adjacent structures with thermal ablation.

Currently, what are the recommended first, second, and third line options for patients with neuropathic pain?

First line therapies: Tricyclic antidepressants, dual NE and serotonin reuptake inhibitors, calcium channel α2-δ ligands (gabapentin and pregabalin), and topical lidocaine.

Second line therapies: Opioid analgesics and Tramadol

Third line: Bupropion, Citalopram, Paroxetine, Antiepileptic medications, other topical ointments (i.e. capsaicin).

Additional references:
Chen H, Lamer TJ, Rho RH, Marshall KA, Sitzman BT, Ghazi SM, Brewer RP. Contemporary management of neuropathic pain for the primary care physician. Mayo Clin Proc. 2004 Dec;79(12):1533-45.

O'Connor AB, Dworkin RH. Treatment of neuropathic pain: an overview of recent guidelines. Am J Med. 2009 Oct;122(10 Suppl):S22-32.

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

Monday, January 23, 2017

Image-Guided Cryoablation for the Treatment of Phantom Limb Pain in Amputees: A Pilot Study


Phantom limb pain (PLP) affects up to 50-80% of patients with limb loss amputations. This condition is defined by unpleasant, often painful, sensations that are perceived to originate from the amputated limb. Prologo et al present the results of a single-arm pilot study with 21 patients investigating the efficacy of percutaneous cryoneurolysis for treatment of PLP refractory to conventional treatments. The study patients underwent a two-step protocol consisting of initial computed tomography-guided perineural injection with 0.25% bupivacaine and betamethasone. If initial injection improved PLP symptoms, the patients underwent cryoneurolysis at a later date. Study endpoints included changes in pain intensity and functional impairment as measured by a visual analog scale and the Roland Morris Disability Questionnaire, respectively. At 7-days post-cryoablation, pain intensity scores decreased by 0.8 (5.4 versus 6.2) and functional impairment decreased by 1.9 (9.4 versus 11.3) compared to baseline; however, these changes were not statistically significant. At 45-days post-cryoablation, pain intensity scores decreased by 3.9 (2.3 versus 6.2) and functional impairment decreased by 8.0 (3.3 versus 11.3) compared to baseline, and these changes were statistically significant (p<0.0001). There were no statistically significant differences in pain intensity and functional impairment scores between the 45-day post-procedure visit and long-term follow-up visits (194 days +/- 99 days). Four patients volunteered to undergo repeat cryoablation and demonstrated consistent response to the second treatment with respect to both functional impairment and pain intensity score improvement. There was 100% technical success in the study with no reported adverse events related to treatment or participation in the study. Six patients (29%) required additional nonsteroidal anti-inflammatory drugs during the initial days following cryoneurolysis due to procedure related pain.




Commentary

This pilot study by Prologo et al provides preliminary data demonstrating safety and efficacy of cryoneurolysis for reducing refractory phantom limb pain. At 45-days post-treatment, patients demonstrated significant decreases in both pain intensity and functional impairment. The study had 100% technical success and no reported adverse events related to treatment or inclusion in the study. Interestingly, pain in the residual limb was a significant covariate for both baseline pain intensity and response to cryotherapy. Patients with residual limb pain had lower baseline pain and less overall change in pain intensity compared to patients without residual limb pain. This study was limited as a pilot study without a control arm or randomization. In addition, the authors did not collect or evaluate medication logs to determine how treatment affected use of pain control medication. The reported exploratory data; however, supports the design of a larger, parallel-arm randomized controlled trial in the future with more comprehensive outcome measurements. Overall, percutaneous cryoneurolysis has the potential be a safe and effective treatment option for refractory PLP.

Click here for abstract

Prologo JD, Gilliland CA, Miller M, Harkey P, Knight J, Kies D, Hawkins CM, Corn D, Monson DK, Edalat F, Dariushnia S, Brewster L. Percutaneous Image-Guided Cryoablation for the Treatment of Phantom Limb Pain in Amputees: A Pilot Study. J Vasc Interv Radiol. 2017 Jan;28(1):24-34.

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

Thomas J. An, BA
Vanderbilt University School of Medicine

Thursday, January 19, 2017

From the SIR residents and fellows section (RFS)


Teaching Topic: Whether or Not to Use Free Hepatic Vein Pressure to Calculate the Portal Pressure Gradient in Cirrhosis.


Martin Rössle, MD, Philipp Blanke, MD, Benjamin Fritz, MD, Michael Schultheiss, MD, and Dominik Bettinger, MD. Free Hepatic Vein Pressure Is Not Useful to Calculate the Portal Pressure Gradient in Cirrhosis: A Morphologic and Hemodynamic Study. J Vasc Interv Radiol 2016; 27: 1130-1137

Click here for abstract

In a recent study published in JVIR, researchers from the University Hospital Freiburg investigated the role of using free hepatic vein pressure in calculating the hepatic venous pressure gradient. Diameter and pressure measurement were obtained in multiple locations within the hepatic vein, IVC, and right atrium on 30 hepatic venograms in 29 consecutive patients with planned TIPS creation. The authors found a wide range of pressure measurements and diameters across the length of the hepatic vein creating a significant amount of variability in measured pressure gradients that were not reflective of the hemodynamic changes occurring within the portal system. This challenges the current guideline recommendations of measurement in the hepatic vein or the IVC, disregarding the right atrium as an internal reference. The manuscript concludes that using the free hepatic vein pressure (FHVP) to calculate the hepatic vein pressure gradient (HVPG) is not recommended given changes with catheter tip position and vein morphology. However, the high agreement between the wedged hepatic vein/IVC pressure gradient (HCPG) and hepatic atrial pressure gradient (HAPG) suggest that both may be used.

Clinical Pearls


What is the significance of the hepatic venous pressure gradient (HVPG)?

The HVPG is the calculated difference of the wedged hepatic vein pressure (WHVP) from the free hepatic vein pressure (FHVP). A value of more than 10 mm Hg is considered clinically significant portal hypertension. A reduction to less than 12 mm Hg or a reduction of more than 10% from the baseline value is associated with decreased risk of variceal hemorrhage and improved survival. Traditionally, FHVP should be measured close to the hepatic vein orifice within a distance of 4-5 cm of the IVC. When pressure measurement differences of more than 1-2 mm Hg exist between the hepatic vein and the IVC, the pressure measured at the IVC at the level of the entrance of the hepatic veins should be used in place of the FHVP.

This study sought to reevaluate the use of HVPG for several reasons. First, in patients with advanced cirrhosis, hepatic veins may be narrowed, irregular, or compressed. This may result in erroneous measurements with an apparently high FHVP and a low HVPG. Second, postprocedural measurement of the FHVP is difficult or impossible. Therefore, measurements are commonly performed in the IVC or right atrium, which is considered the “sea level” of the vascular system and therefore the natural reference for hemodynamic measurements.

What are the recommendations of the Baveno Consensus Workshop?


The most recent expanded Baveno VI Consensus recommends TIPS within 72 hours (ideally < 24 hours) in patients bleeding from esophageal or gastric varices at high risk of treatment failure (Child class C < 14 points or Child class B with active bleeding) after initial pharmacologic and endoscopic therapy (Class 1b; Level A). Persistent bleeding despite combined pharmacologic and endoscopic therapy is best managed by PTFE-covered TIPS (Class 2b; Level B). Rebleeding during the first five days may be managed by a second attempt at endoscopic therapy. If rebleeding is severe, PTFE-covered TIPS is likely the best option (Class 2b; Level B). New guidelines in this workshop now recommend TIPS for patients with refractory ascites who are intolerant to non-selective beta blockers (NSBB) (Class 5, Level D). TIPS can be considered in patients with transfusion-dependent portal hypertensive gastropathy in whom NSBB and/or endoscopic therapies fail (Class 4; Level C). The stepwise approach to management of Budd-Chiari syndrome/hepatic venous outflow tract obstruction is: anticoagulation, angioplasty/thrombolysis, TIPS, and orthotopic liver transplantation (Class 3b; Level B).

Morning Report Questions


What factors may contribute to the inaccuracy of FHVP measurement?

Aside from narrowed, irregular, or compressed veins in patients with cirrhosis, relative obstruction of a hepatic vein by a catheter may erroneously increase the measured FHVP. In this study, the percentage of vessel obstruction by the 8-F catheter (diameter, 2.4 mm) was 40% in the peripheral position and decreased to 10% in the central (proximal) position. Small hepatic veins with a diameter of < 6 mm have a considerable obstruction of 20% or more irrespective of the location of the tip of the catheter. This study found excellent correlation between the wedged hepatic vein/IVC pressure gradient (HCPG) and the hepatic atrial pressure gradient (HAPG), which justifies using either the IVC or right atrium as internal references to calculate the portosystemic pressure gradient, not the free hepatic venous pressure. If using the HAPG, the systemic difference of 2 mm Hg should be regarded by resetting the threshold for symptomatic portal hypertension at an HAPG of 14 mm Hg.



What concerns exist about the use of the right atrium as an internal reference when calculating the portosystemic pressure gradient?

The authors mention previous studies in which pressure measurement in the right atrium is neglected because changes in intraabdominal pressure may affect the portoatrial pressure gradient but not the portohepatic pressure gradient. Therefore, it can be argued that the portosystemic pressure gradient will be significantly higher when using right atrial pressure as an internal reference as compared to using the hepatic veins or IVC. These studies placed sandbags over the abdomen to mimic high intraabdominal pressure, which led to uniform increase in pressure downstream of the obstruction in the hepatic and portal veins but left the right atrium unaffected or even reduced. The authors argue that increased intraabdominal pressure in patients with true ascites reflects an “open” system and that such increased pressures result in a change in their respective blood pools but may have only a short and limited effect on the intravascular pressure.

Additional Citations:
De Franchis, Roberto. “Report of the Baveno VI Consensus Workshop: Stratifying Risk and Individualizing Care for Portal Hypertension.” Journal of Hepatology. 2015 September; 63(3): 743-752.

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

Thursday, January 12, 2017

Management of May–Thurner Syndrome in Adolescents 


Although there is a mature body of evidence supporting the safety and efficacy of endovascular intervention for May-Thurner syndrome (MTS) in adults, few studies have described results of intervention in the pediatric population. Goldman et al present a retrospective, single institution study of 10 adolescent patients, ages 12-18 years, who underwent endovascular therapy for MTS between 1998 and 2015. Six patients had pro-thrombotic risk factors including heritable conditions like factor V Leiden and/or oral contraceptive use. Acute deep venous thrombosis (DVT) was the presentation of 6/10 patients, who were treated with catheter-directed thrombolysis (CDT) alone or in combination with pharmacomechanical thrombolysis. The remaining 4/10 presented with symptoms of chronic venous outflow obstruction. All patients (thrombotic and non-thrombotic) were treated with venoplasty and stenting. Stent models included S.M.A.R.T, Wallstent, and Protégé stents, varying between 12-mm-16-mm diameters. Thrombolysis was technically successful in 4/5 patients and stenting was technically successful in 9/10 patients (the last patient did not have available imaging for review). No periprocedural complications were observed. All patients were treated with systemic anticoagulation for at least 3-months following intervention and were followed for median 32-months (range: 6-109 months). The rates of post-thrombotic syndrome (PTS) following intervention was 0% by Villalta score and 60% by modified Villalta score (designed for use in the pediatric population), and all cases with positive PTS were mild in symptom severity. Iliofemoral patency rates at 12-months were 79% (primary) and 100% (secondary), and at 36-months were 79% (primary) and 89% (secondary). One patient with antiphospholipid syndrome and homozygous MTHFR gene mutation, as well as non-adherence to medical anticoagulation presented with occlusive thrombus 14-months after initial intervention, but no invasive therapy was pursued given relatively mild symptoms.



Commentary


Venothromboembolism (VTE) is rare in the pediatric population, and pediatric MTS therefore remains a nascent area of study, for which optimal therapeutic approach is not fully elucidated. The risks for recurrent DVTs, and long-term debility from PTS in the adult MTS population has been well described, and pediatric patients may suffer similar outcomes without treatment. The experience described by Goldman et al suggests that CDT and stenting techniques may be applied with similar efficacy and safety in the adolescent population as the adult population, suggesting that these techniques should be considered in these patients. In particular, the high primary and secondary patency rates at 12 and 36-months compare favorably to those reported in adults. The authors highlighted the challenges to stenting MTS patients with underlying thrombophilic syndromes, which overall had poorer patency outcomes than those without thrombophilic syndromes and included a case of re-occlusion associated with prothromobotic syndrome and non-compliance with anticoagulation regimen. The study was subject to biases of a small patient population, retrospective imaging and clinical assessment, and non-standardized anticoagulation regimens as well as follow-up times. Furthermore, the majority of patients were of adult body habitus so the endovascular techniques and venous patency outcomes cannot be generalized to younger pediatric patients, who still have significant growth potential. Nonetheless, this study bolsters the limited evidence base for endovascular management of MTS in the pediatric population by demonstrating excellent long-term patency rates and safety profile, concordant with results seen in adults and further follow-up studies would be beneficial.

Click here for abstract

Goldman RE, Arendt VA, Kothary N, Kuo WT, Sze DY, Hofmann LV, Lungren MP. Endovascular Management of May-Thurner Syndrome in Adolescents: A Single-Center Experience. J Vasc Interv Radiol. 2017 Jan;28(1):71-77.

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

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

Wednesday, January 4, 2017

From the SIR Residents and Fellows Section (RFS)


Teaching Topic: Clinical Outcomes following Percutaneous Radiofrequency Ablation of Unilateral Aldosterone-Producing Adenoma: Comparison with Adrenalectomy


Sarwar A, Brook OR, Vaidya A, Sacks AC, Sacks BA, Goldberg SN, Ahmed M, Faintuch S. Clinical outcomes following percutaneous radiofrequency ablation of unilateral aldosterone-producing adenoma: comparison with adrenalectomy. J Vasc Interv Radiol. 2016. 27: 961-7.

Click here for abstract

In this recent manuscript in JVIR, researchers at Beth Israel Deaconess Medical Center compared adrenal RFA with adrenalectomy in treating unilateral aldosterone-producing adenoma (APA). The study included 44 patients with confirmed unilateral APA. Twelve of 44 underwent RFA and 32/44 underwent adrenalectomy. Both RFA and adrenalectomy resulted in normokalemia and normotension in all patients. However, RFA patients had a shorter lenth of stay (0.6 +/- 0.8 d vs. 1.7 +/- 1.4 d) less intraoperative blood loss. In addition, the adrenalectomy patients had procedural complication in 5/32 (15%) versus 0/12 in the RFA group. The authors concluded that RFA has similar effectiveness to adrenalectomy in treating patients with APA with less complications and a shorter hospital stay.

Clinical Pearls


Primary Aldosteronism (PA) is the most common cause of secondary hypertension, with a reported prevalence of 4.3% in the general population with hypertension and >11% in patients referred to specialized centers. Clinical practice guidelines from the Endocrine Society recommend unilateral laparoscopic adrenalectomy for patients with documented unilateral PA.

What patient factors/characteristics have studies shown to be associated with surgical cure of hypertension secondary to PA?

Demographic factors show that a younger age population, females and those with a BMI < 25 kg/m2 have been associated with surgical cure of hypertensin secondary to PA. Other factors that studies have shown to be associated with surgical cure are fewer antihypertensive medications before the procedure and a higher preoperative blood pressure.

Morning Report Questions


What constitutes a cure of hypertension and what constitutes improvement in hypertension from adrenalectomy?

A cure of hypertension is defined as normotension without the use of antihypertensive medications. An improvement in hypertension is normotension on the same regimen of medications that the patient was on prior to the procedure or normotension on a reduced number of antihypertensive medications.

What does The Endocrine Society recommend as the gold standard for laterization of excess hormone production?

The Endocrine Society recommends adrenal venous sampling (AVS) as the gold standard for laterization of excess hormone production. Unilateral production of excess aldosterone is most commonly due to an aldosterone-producing adenoma (APA) or unilateral adrenal hyperplasia.

What were some of the key findings observed in adrenalectomy vs RF ablation of unilateral aldosterone-producing adenoma?

This study demonstrated that RF ablation can achieve clinical outcomes similar to adrenalectomy with lower procedural morbidity in treating patients with AVS-proven unilateral APA. It showed that the efficacy in treating APA was similar with both treatments reducing blood pressure, number of anti-hypertensive medications and both treatments also increasing the serum potassium levels without the need for potassium replacement.

Another important finding in this study was that patients undergoing RF ablation had a significantly higher incidence of intraprocedural hypertensive urgency compared with patients undergoing adrenalectomy. These episodes of hypertensive urgency in the RF group were short in duration (<15 minutes) and were easily reversed by intraprocedural medications without any reported clinical sequelae. This raises an important consideration for future RF ablation procedures such as possibly adding alpha-adrenergic antagonist before the procedure to minimize the catecholamine surges that may occur secondary to incidental ablation of normal adrenal medullary tissue.

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





Friday, December 16, 2016

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

Thursday, December 8, 2016

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