Tuesday, August 16, 2016

Modifications to IRE: Are we there yet?


In an upcoming issue of JVIR, researchers from Stanford University present their experience in producing spherical ablation using irreversible electroporation (IRE) using a single electrode and a grounding pad. The drawbacks to IRE are evident to any interventionalist that regularly uses this treatment technique in clinical practice and any research that addresses these shortcomings should come as welcome news. In short, IRE has some limitations as an ablative tool including cardiac arrhythmias, requirement for chemical paralysis to prevent muscle contractions, and need for placing probes close together. This study investigated two modifications to attempt to address these issues. One is the use of high-frequency IRE (H-FIRE). Besides sounding awesome, H-FIRE uses a rapid burst of 0.25-5-┬Ás alternating-polarity pulses instead of the long-duration monopolar IRE pulse. This produces less susceptibility to distortions in the magnetic field distribution created by tissue heterogeneities and produces more predictable treatment zones. Further, H-FIRE inhibits stimulation of action potentials and treats without inducing muscles contractions. However, H-FIRE has been limited by the small size and “peanut” shape of the ablation zone. This study included a modified probe design to include a single electrode at the target site and a distal grounding pad. This differs from the traditional design with two separate electrical conductors co-located in the same tumor volume. Computed simulations were performed by using varying voltages, electrode exposure lengths, and tissue types. A vegetable (potato) tissue model was then used to compare ablations created by conventional and high-frequency IRE protocols by using the two collinear electrodes or a single electrode configured with a grounding pad. In addition, the new electrode configuration was evaluated in ex vivo liver tissue. Researchers found that the new probe + grounding pad configuration produced larger and more spherical ablation volumes than the traditional configuration in computed simulations and tissue models. Potato model studies verify that the probe + grounding pad configuration produces larger and more spherical ablations than those produced by the traditional method. The researchers made no comment regarding the flavor of the ablated potato.

Commentary:


This paper does a very good job at identifying an existing treatment modification (H-FIRE) and modifying that further with creating a single probe system with the use of a grounding pad. As many interventional oncologists would attest, it would be very advantageous in clinical practice to have an IRE system that used a single probe and was able to create spherical ablation zones. There are some additional hurdles for this technical modification. As mentioned in the paper, the creation of large ablations is theoretically possible with the new configuration if voltages are between 3,000 and 5,000 V. However, 3,000 V is the highest voltage reported for clinical IRE treatments, and the thermal implications of these higher voltages are not fully understood. In addition, in the new configuration, the electrical current will travel between the single electrode and the grounding pad. There is the potential for nontarget thermal and electrical effects. Despite these obstacles, many interventionalists will be looking forward to seeing this technology progress through development to the market.



Click here for abstract

Sano MB, Fan RE, Hwang GL, Sonn GA, Xing L. Production of Spherical Ablations Using Nonthermal Irreversible Electroporation: A Laboratory Investigation Using a Single Electrode and Grounding Pad. J Vasc Interv Radiol. doi: 10.1016/j.jvir.2016.05.032

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

Monday, August 1, 2016

Results from the RENOVA study show superiority of stent graft to balloon angioplasty in the treatment of arteriovenous graft stenosis


A national team of researchers led by Dr. Ziv Haskal of the University of Virginia have recently published their 2-yr results from the Prospective, Randomized, Concurrently-Controlled Study of an ENdOVAscular Stent Graft. The RENOVA trial, was conducted at 28 clinical sites in the U.S. and was designed to compare the use of an ePTFE stent graft to PTA alone for the revision of AV access graft-venous anastomotic stenosis through 2 years. A total of 270 patients were enrolled with malfunctioning AVG anastomotic stenoses of ≥50%. 138 patients underwent placement of a stent graft (SG) and 132 received angioplasty (PTA) alone. At 12 months, treatment area primary patency (TAPP) was: SG 47.6% vs. PTA 24.8% (p< 0.001) and access circuit primary patency (ACPP) was SG 24% vs. PTA 11% (p=0.007). At 24 months, TAPP was: SG 26.9% vs. PTA 13.5% (p<0.001) and ACPP was SG 9.5% vs. PTA 5.5% (p=0.01). The estimated number of re-interventions before graft abandonment was 3.4 for the SG group vs. 4.3 for PTA group. There were no significant differences in the adverse events (p>0.05) excepting restenosis requiring reintervention rates of 82.6% in PTA patients vs. 63.0% in SG (p<0.001). The authors concluded that at 2 years, Stent graft use provided a “sustained, greater than two-fold advantage over angioplasty in treatment area and overall access patency.”

Discussion


The FLAIR trial from 2010 showed 6-month superiority of the SG for both prolonging uninterrupted access function and patency of the target stenosis and led to FDA approval of the device. The RENOVA study has replicated and affirmed the pivotal trial results, extending the follow up to 2 years, and establishing the long-term superiority of this stent-graft for revision of failing anastomoses in prosthetic grafts as compared to repeated PTA. As detailed in the paper, the healthcare costs of maintaining a failed AV access are substantial. Further, given the burden associated repeat interventions upon patients, the use of SGs in this clinical scenario may offer significant advantages to the dialysis patient population and to the healthcare system as a whole.

Click here for full text

Haskal, Ziv J., et al. "Prospective, Randomized, Concurrently-Controlled Study of a Stent Graft versus Balloon Angioplasty for Treatment of Arteriovenous Access Graft Stenosis: 2-Year Results of the RENOVA Study." Journal of Vascular and Interventional Radiology 27.8 (2016): 1105-1114.

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

Tuesday, July 12, 2016

Can IVUS-Guided TIPS be more than just “Fancy TIPS”?


Intravascular ultrasound guided access to a portal vein during TIPS creation is an alternate technique to the conventional method of fluoroscopically guided access following hepatoportal venography. This retrospective study was performed to compare three parameters: mean time to PV access, radiation dose, and capsular perforation, between the intravascular US guided access (n=55) and conventional fluoroscopically guided access (n=54) groups. Further, the results were stratified by operator experience (10 total operators; 5 with <20, and 5 with > 20 conventional TIPS procedures before this study, classified as inexperienced, and experienced, respectively). There was no significant difference in the sex, age, BMI, etiology of cirrhosis, or indication for TIPS, in the two study populations. The study found that parameter mean time to PV access was significantly lower for the intravascular US guided access group overall, but showed no difference when comparing experienced operators only. Further, parameter mean time to PV access continued to decrease over the course of the study in the US guided access group. In measuring radiation dose and capsular perforation, both were statistically lower in the intravascular US guided group than the conventional group.

Comment:


Alternate techniques to gaining portal vein access during TIPS include three dimensional navigation using fusion, prior percutaneous PV marking, utilization of cone beam CT, transabdominal ultrasound, and intravascular ultrasound. While there have been studies comparing the conventional vs. intravascular US guided PV access techniques in the past, this is the first one to take operator experience into account, and has a slightly higher number of patients (109 vs. 100). This study also does not compare the number of needle passes performed to access the PV, as this was felt to be a subjective measurement. Further, time for femoral vein access and IVUS set-up was not included in this study nor was the added cost associated with the device. As technology progresses, cost, operator preference, and quality control will dictate whether such ancillary techniques will contribute in regularly to TIPS creation.



Click here for abstract

Pillai, Anil K., et al. Utility of Intravascular US–Guided Portal Vein Access during Transjugular Intrahepatic Portosystemic Shunt Creation: Retrospective Comparison with Conventional Technique in 109 Patients. Article in press. doi: 10.1016/j.jvir.2016.05.010

Post Author:
Nabeel Mecci, MD
University of Virginia
PGY-2 Radiology Resident

Thursday, June 2, 2016

New Study Investigates Retrieval and Complication Rates of Denali and Celect IVC Filter


In an article in press, Researchers from the University of Chicago compared the indwelling and retrieval complications of Denali and Celect filters placed in the infrarenal IVC. This retrospective review was conducted over 2 years and included 171 Denali and 162 Celect filters. 91% (303) of the filters were placed from a jugular approach. Follow-up CT images were evaluated in 58 filters from each group. The Denali group showed significantly lower incidence of caval strut penetration (1 vs 12) and tilt (1 vs 15). Retrieval attempts were made on 43 Denali filters and 53 Celect filters with similar indwelling times. There was significantly less fluoroscopy time in the Denali group (3.1 vs 6.0 min). In addition, there was a trend toward fewer “complex” retrievals in the Denali group (2 vs 10, p = 0.06). ​Complex retrieval was defined as “successful retrieval attempts in which conventional retrieval techniques, failed necessitating one of the adjunctive retrieval methods described earlier.” It is noted that only 5 of the 15 tilted Celect filters presented for retrieval and 3 of those 5 required snare-over-guide wire loop technique or forceps for retrieval. Complex retrievals were associated with increased fluoro time (14.3 vs 3.2 min) and increased dose (333.4 vs 149.5 mGy).

Discussion


While the current study demonstrates that “complex” techniques are needed more frequently in retrieval of Celect filters when compared with Denali filters, it remains to be seen if this will significantly impact practice pattern. “Complex” retrievals are becoming much less, well.… complex. Given increased familiarity with advanced techniques, many centers are seeing a marked decrease in fluoro times for even the most challenging retrievals. When combined with overall decreasing rates of strut penetration and tilt (even in the Celect group), the result is low average rates of fluoroscopy time when compared to the group as a whole (Celect 6.0 min in the current study). Further, depending on local pricing, there is likely an increased cost for Denali when compared to some of the older generations of IVC filters. Before a practice considers changing filters, a comprehensive view of potential costs (clinical and financial) of retrieval should be thoroughly considered.



Click here for abstract

Bos AS, Tulius T, Patel M, Leef JA, Navuluri R, Lorenz JM, Van Ha TG. Indwelling and retrieval complication of Denali and Celect infrarenal vena cava filters. J Vasc Interv Radiol. June 2016. doi: 10.1016/j.jvir.2016.03.034

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

Monday, May 23, 2016

Endologix Unibody Endograft performance in Aortoiliac occlusive disease


The field of endograft manufacture and design has been an active one with improved performance and lower profile devices under continuous development. A multicenter retrospective review was conducted to evaluate safety, efficacy and early patency rates of the 17Fr ipsilateral, 9Fr contralateral Endologix AFX unibody endograft in the treatment of aortoiliac occlusive disease and recently published in the European Journal of Vascular and Endovascular Surgery.

91 patients were treated for aortoiliac occlusive disease. Patients with concomitant aortic aneurysm were excluded. Mean follow up was 22.2 months. Technical success was 100%. Complication rate was 22% with 1 mortality in the 30 day follow up period from extensive pelvic thromboembolism. At 1 year 73% of patients experienced improvement in Rutherford stage of -3 or greater compared with baseline. At all points primary patency were >90%, assisted patency rates were >98% and secondary patency rates were 100%.



Commentary:


Use of the AFX unibody stent-graft had a high rate of technical success and a low morality rate. Patency rates were comparable to with open aortobifemoral bypass, kissing stent and CERAB techniques. This study is the largest so far in the evaluation of the AFX unibody graft performance. Notably 82% of patients treated in this study had baseline TASC D disease making the already favorable patency data arguably even more so. 41% of these cases were done percutaneously with hemostasis achieved using the Proglide (Abbott Vascular, Abbott Park, IL, USA). Although the authors indicate that the use of re-entry devices was not necessary, they say these may be helpful to obtain femoral-femoral wire access in some cases. It is not clear what proportion of aortoiliac lesions were successfully crossed in an intraluminal position and which if any required subintimal angioplasty (SIA). Furthermore if there were lesions which required SIA it is unclear if these were included.

Although the complication rate was high (22%) none of the complications appear to be device related. The majority of the complications appear to be related to the open femoral access utilized in 59% of cases. The incidence of groin related complications in this study is comparable with that found in open surgical repair and may reflect that this subset of patients is exposed to the same risks found in open surgery. Overall, this manuscript serves as continued support in using the Endologix device in cases of aortoiliac occlusive disease in which the cranial extent of occlusion makes kissing stents unfavorable.

Click here for abstract

Maldonado TS, Westin GG, Jazaeri O, et al. Treatment of aortoiliac occlusive disease with the Endologix AFX unibody endograft. Eur J Vasc Endovasc Surg. May 2016. doi: 10.1016/j.ejvs.2016.04.003

Post Author:
Marco Ugas, MD
University of Virginia
PGY-5 Radiology Resident

Wednesday, March 16, 2016

SIR 2016 Vancouver: Early Career Section "Exploring IR" Session


Seeking questions for the "In Your Experience" Panel


During the 2016 Annual Scientific Meeting in Vancouver, BC, the Early Career Section will be hosting the several meetings and events focused on addressing the needs and interests of young professionals. One of these meetings is a session in SIR targeted toward Interventionalists early on in their career.

The "In Your Experience" Panel will feature panelists that have extensive experience in both the private practice setting and academics. They will be giving answers to questions provided by YOU. Did you ever wonder how they managed to maintain a strong presence in the PVD space without alienating their vascular surgery colleagues? How did they maintain a close relationship with diagnostic radiology during years that their interventional practice was not profitable? What would they be worried about if they were just starting their career?

Exploring IR

Saturday, April 2, 2016
3:30- 5:30 pm

· Participating in Clinical Research – Wael Saad, MD, FSIR
· Developing & Maintaining a Referral Base – Elizabeth B. Spencer MD, FSIR
· Dealing with Complications and malpractice – John Cardella, MD, FSIR
· Business of Medicine – What you need to know as an early IR – Katherine Krol, MD, FSIR
· Transitioning from MSC to RFS and ECS – Geogy Vatakencherry, MD
· Value SIR offers young IR’s - Alan Matsumoto, MD, FSIR

“In Your Experience” Expert Panel

Panelists:

· Bayne Selby, MD
· Parag Patel, MD, FSIR
· Keith Sterling, MD, FSIR
· James Benenati, MD, FSIR
· Anne Roberts, MD, FSIR

This is your chance to ask the tough questions to a group of well-respected interventional radiologists. Anytime between now and March 25th , submit any questions toccouture@sirweb.org and come to the session to hear the answers by our expert panel.

Wednesday, February 24, 2016

Cryoneurolysis in Peripheral Neuropathic Pain


Neuropathic pain is a growing problem as the population ages and the prevalence of diabetes increases. Multiple methods of have been employed to treat neuropathic pain, including medical therapies, local anesthetics, and more invasive procedures such as spinal cord stimulators and neurolysis. Investigators from SUNY Stony Brook evaluated the use of ultrasound guided cryotherapy in this difficult patient population. Patients were selected based on inclusion criteria such as: failure of a first or second line therapy, evaluation by a pain physician before initiating therapy, and a history of response to nerve blocks. Exclusion criteria included an inability to participate in follow up assessments of pain levels. In total, 22 patients underwent ablation and were followed at 1 week and 1, 3, 6, 9, and 12 month intervals. Of these patients, 11 required repeat cryoneurolysis within 12 months of the initial procedure. The average pain score before treatment was 8.3 +/- 1.9. Pain scores after treatment were 2.3 +/- 2.5 at 1 month, 3.2+/- 2.5 at 3 months, 4.7 +/- 2.7 at 6 months, and 5.1 +/- 3.7 at 12 months. In addition to these findings, the study concluded that the regeneration of the treated nerve was related to ablation time. For example, authors found that 1 minute of ablation time corresponded to 1 month of time for nerve regeneration.

Commentary:


This study presents cryotherapy as an effective and safe alternative to other treatment methods for neuropathic pain. This technique provides statistically significant pain relief for the patients at every time point examined. Additional studies will be required for further evaluation of this technique, including future prospective studies to determine optimal ablation time and treatment intervals. Although the study is limited by sample size, number of ablations during the evaluation period, and concomitant pain management therapy, 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.




Click here for abstract

Yoon JHE, Grechushkin V, Chaudry A, Bhattacharji P, Durkin B, Moore W. Cryoneurolysis in Patients with Refractory Chronic Peripheral Neuropathic Pain. J Vac Interv Radiol 2016; 27:239-243.

Post Author:
Brian Gardner, MD
VIR Pathway Resident at University of Virginia